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American Urological Association, Inc. Nephrolithiasis Clinical Guidelines Panel:

Report on the Management ofStaghorn Calculi

Clinical Practice Guidelines


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The Nephrolithiasis Clinical Guidelines Panel consists of board-certified urologists who are experts instone disease. This Report on the Management of Staghorn Calculi was extensively reviewed by over 50 urolo-gists throughout the country in the Fall of 1993. The Panel finalized its recommendations to AUAs PracticeParameters, Guidelines and Standards Committee, Chaired by Winston K. Mebust, MD, in December 1993.The AUA Board of Directors approved these practice guidelines at its meeting in January 1994.

The Summary Report also underwent independent scrutiny by the Editorial Board of the Journal of Urology, was accepted for publication in March 1994, and appeared in its June issue. A guide to assist patientsdiagnosed with this condition has also been developed. The Technical Supplement to this Report is availableupon request.

The American Urological Association expresses its gratitude for the dedication and leadership demonstrat-ed by the members of the Nephrolithiasis Clinical Guidelines Panel in producing the AUAs first explicit guide-line using the Eddy methodology.

Nephrolithiasis Clinical Guidelines PanelMembers and Consultants

Dean G. Assimos, M.D.Assoc. Professor of Surgical SciencesDepartment of UrologyThe Bowman Gray School of MedicineWake Forest UniversityWinston-Salem, North Carolina

Stephen P. Dretler, M.D.Director, Kidney Stone CenterMassachusetts General HospitalBoston, Massachusetts

Robert I. Kahn, M.D.Chief of EndourologyCalifornia Pacific Medical CenterSan Francisco, California

James E. Lingeman, M.D.Director of ResearchMethodist HospitalInstitute for Kidney Stone Disease

Associate Clinical Instructor in Urology

Indiana University School of MedicineIndianapolis, Indiana

Joseph W. Segura, M.D., ChairmanThe Carl Rosen Professor of UrologyDepartment of UrologyThe Mayo ClinicRochester, Minnesota

Joseph N. Macaluso, Jr., M.D.Medical Dir.; Dir. of Grants & ResearchUrologic Institute of New OrleansAssoc. Professor & Dir. of Endourology,Lithotripsy & Stone Disease

Louisiana State Univ. Medical Center

School of MedicineNew Orleans, Louisiana

David L. McCullough, M.D.William H. Boyce ProfessorChairman, Department of UrologyThe Bowman Gray School of MedicineWake Forest UniversityWinston-Salem, North Carolina

Claus G. Roehrborn, M.D.Facilitator Coordinator

Hanan Bell, Ph.D.Methodology and Statistical Consultant

Curtis ColbyEditor

Patrick FlorerComputer Database Design Consultant

Glenn M. Preminger, M.D., FacilitatorProfessor, Department of UrologyDuke University Medical CenterDurham, North Carolina


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Urologists and patients can choose from many alternativestoday for management of renal and ureteral calculi. The improve-ments in urologic equipment, radiologic technology, and interven-tional radiologic techniques have dramatically increased the meansavailable for stone removal.

As a consequence, however, questions have arisen regardingapplications of particular modalities to treat the various types of stone disease. To help clarify treatment issues, the AmericanUrological Association, Inc., convened the Nephrolithiasis ClinicalGuidelines Panel in 1990 and charged it with the task of producingpractice recommendations based on outcomes evidence from thetreatment literature.

The recommendations in this Report on the Management of Staghorn Calculi are to assist physicians in the treatment specifical-ly of struvite staghorn calculi. Although relatively uncommon,

these kidney stones present serious problems because they occur inthe presence of urinary tract infections and because the stonesthemselves are infected. Treatment must remove stones completelyto eradicate all infected stone material.

The choice of treatment can be a source of controversy giventhe range of modalities and techniques now available, each withadvantages and disadvantages. This makes struvite staghorn calculian especially appropriate subject for evidence-based recommenda-tions.

A Patients Guide and more detailed technical appendices areavailable upon request.

Introduction


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Production and layout by

Lisa EmmonsTracy Kiely

Betty Roberts

Copyright 1994American Urological Association, Inc.

ContentsExecutive Summary: Treatment of staghorn calculi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Methodology for development of treatment recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Background: Staghorn calculi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Treatment outcomes and alternative modalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2Treatment recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2Limitations in the treatment literature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Chapter 1: Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5Literature search . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5Article selection and data extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6Evidence combination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

Chapter 2: Staghorn calculi and their management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Treatment Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Chapter 3: Outcomes analysis for staghorn treatment alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12Direct and indirect outcomes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12Combining outcome evidence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12The balance sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Analysis of the balance sheet outcomes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Chapter 4: Staghorn treatment recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19Treatment outcomes and treatment recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19The patient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19Recommendations: Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20Recommendations: Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20Recommendations: Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Recommendation limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21Basic research needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

Appendix A: Data presentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A.1

Appendix B: Data abstraction worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B.1

Appendix C: Description of available techniques for management of renal and ureteral calculi . . . . . . . . . . . .C.1Shock-wave lithotripsy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .C.1Percutaneous nephrolithotomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .C.3Ureteroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .C.4

Open lithotomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .C.5

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .I.1


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Executive Summary: Treatment of staghorncalculi

METHODOLOGY FOR DEVELOPMENT OFTREATMENT RECOMMENDATIONS

In developing recommendations for managingstaghorn calculi, the AUA Nephrolithiasis ClinicalGuidelines Panel reviewed the available literatureon treatment of struvite staghorn calculi. Relevantarticles were selected for data extraction, and thepanel devised a comprehensive data-extractionform to capture as much pertinent information aspossible. Data analysis was conducted using theconfidence profile method developed by Eddy andHasselblad [Eddy, 1989; Eddy, Hasselblad, andShachter, 1990]. Chapter 1, Methodology, pro-vides a full description of the process.

BACKGROUND : S TAGHORN CALCULIStaghorn calculi are stones that fill the major

part of the collecting system. Typically, suchstones will occupy the renal pelvis, and branchesof the stone will extend into the majority of thecalices. The term partial staghorn is often usedwhen a lesser portion of the collecting system isoccupied by stone. There is, unfortunately, noagreement on how these terms should be defined,and the term staghorn is often used irrespectiveof the percentage of the collecting system occu-pied.

There is also no widely accepted way to expressthe size of a staghorn calculus. As a result, stonesof widely different volumes are all referred to asstaghorns. Staghorn calculi are usually made of struvite (magnesium ammonium phosphate) withvariable amounts of calcium, but stones made of cystine, calcium oxalate monohydrate, and uric

acid can all fill the collecting system. Such stonesare frequently found intermixed with struvite cal-culi in many series reported in the literature.

The majority of staghorn stones are composedof struvite. These stones tend to be soft, and theirradiologic appearance varies from relatively faintto moderately radiopaque. It is generally possibleto predict on the basis of a plain x-ray film that astaghorn stone is composed of struvite.

These stones are also called infected stones orinfection stones because they occur only in thepresence of urinary tract infection and only whenthe infection is secondary to organisms that elabo-rate the enzyme urease, which splits urea [Bruceand Griffith, 1981]. Cultures of pieces of struvitestones, taken both from the surface and from in-side, have demonstrated that bacteria reside insidethe stones and that the stones themselves are in-fected in contrast to stones made of cystine, cal-

cium oxalate monohydrate, or other substances[Nemoy and Stamey, 1971].An untreated struvite staghorn calculus will in

time destroy the kidney, and the stone has a signifi-cant chance of causing the death of the affectedpatient [Rous and Turner, 1977; Koga, Arakai,Matsuoka, et al., 1991]. Moreover, struvite stonesmust be removed in their entirety to be certain of eradicating all of the infected stone material. If allof the infected material is not removed, the patientwill continue to have recurrent urinary tract infec-tions and the stone will eventually regrow. It may

be possible to sterilize small amounts of struvite,but how much of the stone can be sterilized is un-certain and unpredictable [Pode, Lenkovsky, Sha-piro, et al., 1988; Michaels and Fowler, 1991].

The panel found four modalities reported in theliterature to be potential alternatives, on thestrength of the evidence, for treating patients withstruvite staghorn calculi:

Open surgery referring to any method of open surgical exposure of the kidney and re-moval of stones from the collecting system;

Percutaneous nephrolithotomy (PNL) ; Extracorporeal shock-wave lithotripsy

(SWL) ; and Combinations of PNL and SWL .Because the panel was unable to conduct direct

assessments of patient preferences, panel membersthemselves acted as patient surrogates judgingtreatment choices on the basis of probable out-comes.


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TREATMENT OUTCOMES ANDALTERNATIVE MODALITIES

After reviewing the literature and analyzing thedata, the panel concluded that the following out-come probabilities are the most significant in set-

ting forth recommendations for treatment of stru-vite staghorn calculi:

The probability of being stone free followingtreatment;

The probability of undergoing secondary, un-planned procedures; and

The probability of having complications asso-ciated with the chosen primary treatmentmodality.

The four modalities of open surgery, PNL, SWL,and combination PNL and SWL are all reasonabletreatment alternatives for patients with struvitestaghorn calculi. However, outcome probabilitiesdiffer markedly among the four. The followingstatements are based on both statistical analysis of abstracted data from the treatment literature andexpert opinion. They form the basis of the panelsrecommendations.

The risk of having residual fragments followinginitial treatment is clearly higher after shock-wavelithotripsy monotherapy than after percutaneousnephrolithotomy, combination therapy, or open sur-gery.

It is the expert opinion of the panel that residualfragments of infected calculi left in the renal col-lecting system may be associated with recurrentinfections and eventual regrowth of these fragmentsinto significant stones leading to additional morbid-ity, although literature to support this opinion isscarce.

Shock-wave lithotripsy monotherapy carries ahigh probability of unplanned secondary proce-dures.

Percutaneous nephrolithotomy, combinationtherapy, and open surgery are more likely to re-quire general or regional anesthesia.

The chance that a blood transfusion will berequired is greater for percutaneous nephrolithoto-my, combination therapy, and open surgery than forshock-wave lithotripsy monotherapy.

Rates of complications following the four treat-ment modalities differ significantly for each modal-ity. From the patients viewpoint, a complicationmay have the same importance as a secondary, un-planned procedure, inasmuch as it may require asecond anesthetic procedure or prolong the

patients hospital stay. Therefore, an analysis com-bining secondary, unplanned procedures and thecomplications associated with the primary treat-ment modalities chosen may accurately reflect thepatients viewpoint regarding desirability or unde-sirability of a given intervention.

Of all four treatment modalities, shock-wavelithotripsy monotherapy has the highest combinedcomplication and secondary, unplanned interven-tion rate. However, the complications associatedwith shock-wave lithotripsy tend to be less severethan those associated with percutaneous nephrolith-otomy, combination therapy, or open surgery.

The peer-reviewed literature does not stratifyoutcomes appropriately by either size or composi-tion of staghorn calculi or the anatomy of the col-lecting system. Nevertheless, the panel believesthat these factors impact the outcomes of alterna-

tive treatment procedures.Also, when choosing a treatment alternative,

special circumstances such as the patients overallhealth, body habitus, and other medical problemsneed to be taken into consideration by the treatingphysician.

TREATMENT RECOMMENDATIONSThe AUA Nephrolithiasis Clinical Guidelines

Panel considered, in its recommendations, a total of five methods for managing struvite staghorn calculi including watchful waiting or observation, aswell as the four active modalities: (1) open sur-gery, (2) percutaneous nephrolithotomy (PNL),(3) extracorporeal shock-wave lithotripsy (SWL),and (4) combinations of PNL and SWL.

Levels of flexibilityThe panel graded recommendations for treat-

ment by three levels of flexibility, based primarilyon the strength of the scientific evidence for esti-mating outcomes of interventions. A standard isdefined as the least flexible of the three; a guide-line, more flexible; and an option, the most flex-

ible. These three levels of flexibility [Eddy, 1992]for treatment recommendations are defined on page5.

The patientPanel recommendations for the treatment of

staghorn calculi apply to standard and nonstandardpatients whose stones are presumed to be com-posed of struvite (magnesium ammonium phos-phate).


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Guidelines

1. As a guideline, percutaneous stone removal, followed by shock-wave lithotripsyand/or repeat percutaneous procedures as warranted, should be utilized for moststandard patients with struvite staghorn calculi, with percutaneous lithotripsy beingthe first part of the combination therapy.

2. As a guideline, shock-wave lithotripsy monotherapy should not be used for moststandard patients as a first-line treatment choice.

3. As a guideline, open surgery (nephrolithotomy by any method) should not be used formost standard patients as a first-line treatment choice.

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Standards1. As a standard, a newly diagnosed struvite staghorn calculus represents an indication

for active treatment intervention. Although this recommendation was not formallysubjected to data abstracting and statistical methods, the panel strongly believes basedon expert opinion that a policy of watchful waiting and observation is not in the bestinterest of the standard patient with struvite staghorn calculi.

2. As a standard, a patient with a newly diagnosed struvite staghorn calculus must beinformed about the four accepted active treatment modalities, including the relativebenefits and risks associated with each of these treatments.

Options

1. As options, shock-wave lithotripsy monotherapy and percutaneous lithotripsymonotherapy are equally effective treatment choices for small-volume struvite

staghorn calculi in collecting systems which are of normal or near normal anatomy.2. As an option, open surgery is an appropriate treatment alternative in unusual

situations where a staghorn calculus is not expected to be removable by a reasonablenumber of percutaneous lithotripsy and/or shock-wave lithotripsy procedures.

3. As an option for a patient with a poorly functioning, stone-bearing kidney,nephrectomy is a reasonable treatment alternative.

RECOMMENDATIONS


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A standard patient is defined as an adultpatient who has two functioning kidneys (functionof both kidneys relatively equal) or a solitary kid-ney with substantially normal function, and whoseoverall medical condition, body habitus, and anato-my permit performance of any of the four acceptedactive treatment modalities including use of anes-thesia.

A nonstandard patient is defined as one with astruvite staghorn stone who does not fulfill theabove criteria. For this patient, the choice of avail-able treatment options may be limited to three oreven fewer of the four accepted active treatmentmodalities, depending on individual circumstances.

The recommended standards and guidelines onpage 3 apply to the treatment of standard patients,followed by options for nonstandard patients.

LIMITATIONS IN THETREATMENT LITERATURE

Limitations to the process of developing treat-ment recommendations became apparent during thepanels review of the literature. Most obviously,for the purpose of this document, there is no uni-form system of categorizing staghorn calculi, no

standard method of describing the collecting sys-tem, and no widely accepted system of reportingthe size of staghorn calculi.

Few prospective, randomized, controlled studieshave been conducted concerning the treatment of struvite staghorn calculi. In addition, there is nouniform system in the literature for reporting out-comes following treatment for struvite staghorncalculi.

Further uncertainty stems from differences inhealth care delivery systems in various countries asthey impact the outcomes reported in the literature.Variability in the data leads to uncertainty in out-come estimates, which leads to flexibility in rec-ommendations. This limitation applies to a varietyof outcomes.

Notwithstanding these limitations, the panelbelieves that the standards, guidelines, and optionspresented are well supported by the data reviewed.Recommendations are founded primarily on thedata and partially on the expert opinion of panelmembers. Outcomes for which there is consider-able uncertainty are clearly identified as such in thedocument. Whenever the panels expert opinionprevailed over the limited amount of available data,this is specified in the document as well.


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The recommendations in this Report on the Management of Staghorn Calculi were developedfollowing an explicit approach to the developmentof practice policies [Eddy, 1992], as opposed to animplicit approach relying solely on expert opinionwithout any open description of the evidence con-sidered.

The explicit approach attempts to provide mech-anisms for arriving at recommendations that takeinto account the relevant factors for making selec-tions between alternative interventions. Such fac-tors include estimation of the outcomes from theinterventions, consideration of patient preferences,and assessing when possible the relative priority of the interventions for a share of limited health careresources. Emphasis is placed on the use of scien-tific evidence in estimating the outcomes of theinterventions.

In developing the recommendations in thisreport, an extensive effort was made to review theliterature on staghorn stones and to estimate theoutcomes of the alternative treatment modalities asaccurately as possible. The Nephrolithiasis Clin-ical Guidelines Panel members themselves servedas proxies for patients in considering preferences

with regard to health and economic outcomes.The review of the evidence began with a litera-

ture search and extraction of data as describedbelow. The data available in the literature weredisplayed in evidence tables. From these tables,the panel developed estimates of the outcomesfrom the various interventions (shock-wave litho-tripsy, percutaneous nephrolithotomy, combinationshock-wave lithotripsy percutaneous stone removaland open removal). The panel used the FAST*PRO meta-analysis package as described below tocombine the evidence from the various studies.These estimates of outcomes are arrayed on thebalance sheet on page 13.

The panel generated recommendations based onthe outcomes shown in the balance sheet. Theserecommendations were graded according to threelevels of flexibility, based on the strength of theevidence and on amount of variation in patientpreferences. The three levels of flexibility fortreatment recommendations [Eddy, 1992] are de-fined as follows:

1. Standard: A treatment policy is considered astandard if the health and economic outcomes of the alternative interventions are sufficientlywell-known to permit meaningful decisions andthere is virtual unanimity about which interven-tion is preferred.

2. Guideline: A policy is considered a guideline if the health and economic outcomes of the inter-ventions are sufficiently well-known to permitmeaningful decisions, and an appreciable butnot unanimous majority agree on which inter-vention is preferred.

3. Option: A policy is considered an option if (1) the health and economic outcomes of theinterventions are not sufficiently well-known topermit meaningful decisions, (2) preferencesamong the outcomes are not known, (3) pa-tients preferences are divided among the alter-native interventions, and/or (4) patients areindifferent about the alternative interventions.A standard has the least flexibility as a treat-

ment policy. A guideline has significantly moreflexibility, and options are even more flexible. Asnoted in the definitions, options can exist because

of insufficient evidence or because patient prefer-ences are divided. In the latter case particularly,the panel considered it important to take into ac-count likely preferences of individual patientswhen selecting from among alternative interven-tions.

LITERATURE SEARCHA literature search was performed utilizing

MEDLINE. Articles retrieved from MEDLINEincluded all manuscripts related to renal calculipublished from 1966-1992. Articles prior to 1966were identified by hand searching bibliographiesand reference lists from other articles. Complete-ness of the search was confirmed by cross-check-ing indices of important journals. Journals deemedimportant, but not listed on MEDLINE (such asThe Journal of Endourology ), were also searched.The total yield was 1,250 articles. The specifics of the MEDLINE search criteria are included in theTechnical Supplement.

Chapter 1: Methodology


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dom-effects, or hierarchical, model was used tocombine the studies.

A random-effects model assumes that for eachsite there is an underlying true rate for the out-comes being assessed. It further assumes that thisunderlying rate varies from site to site. This site-

to-site variation in the true rate is assumed to benormally distributed. The method of meta-analysisused in analyzing the staghorn data attempts todetermine this underlying distribution.

The results of the confidence-profile method areprobability distributions. They can be describedusing a mean or median probability with a confi-dence interval. In this case, the 95-percent confi-dence interval is such that the probability (Bayes-ian) of the true value being outside the interval is 5percent.

The probability distribution can be displayed

graphically (as a density function). This graphindicates the probability of any interval as the areaunder the graph on that interval. Thus, if a curveon a graph is very sharply peaked, the area underthe curve is narrow indicating a narrow confidenceinterval. If a curve is relatively flat, this indicatesa wide confidence interval. The total area underthe graph is always equal to 1.

The three graphs that follow illustrate a simpleexample of the use of the FAST*PRO software.Two studies looked at a certain outcome after atreatment for a given disease. In each study, 75percent of the patients had the outcome. The firststudy had a total of 20 patients, and the second hada total of 1,000. If the software is used to updatethe probabilities for each site, the resultant (poste-rior) probability distributions of the true probabili-ty of the outcome can be graphed for each study.

Note that both curves in the graph center on 75percent, but the curve for the first study is muchflatter. There is a much larger uncertainty aboutthe true value with 20 patients studied than with asample of 1,000. Figure 2 adds a third study of 600 patients with 400 (66.7 percent) having the

outcome. This study centers over a different pointand is intermediate in height between the first twostudies.

If these studies are combined using the methoddescribed above, the result is a combined profile(Curve 4 in Figure 3). This profile is very narrowindicating that there is little difference among stud-ies. Since two of the studies have the same resultand the other is close, it is not surprising that therewould be minimal site-to-site variation suggestedby these studies.

The method of computation is Bayesian innature. This implies the assumption of a priordistribution that reflects knowledge about the prob-ability of the outcome before the results of anyexperiments are known. The prior distributions

7

Figure 1. Confidence profiles for studies 1 (15 of 20 pts.) and2 (750 of 1000 pts.)

Probability

Figure 2. Confidence profiles for studies 1 (15 of 20 pts.), 2(750 of 1000 pts.), and 3 (400 of 600 pts.)

Probability

Figure 3. Confidence profiles for studies 1, 2, and 3 andcombined profile 4 (hierarchical Bayes)

Probability


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selected for this analysis are among a class of noninformative prior distributions, which meansthat they correspond to little or no preknowledge.The existence of such a prior can cause small chan-ges in results, particularly for small studies. In theforegoing example, for instance, the mean of the

distribution for the sample of size 20 is 0.74 ratherthan 0.75. The effect of the prior distribution is toslightly discount the value of the experiment. Thiseffect will not be pronounced except in very smallstudies, and the combination of multiple studieswill reduce this tendency further.

For the statistically sophisticated reader, theprior distribution for all probability parameters isJeffereys prior (beta distribution with both parame-ters set to 0.5). The prior for the variance for theunderlying normal distribution is gamma distrib-uted with both parameters set to 0.5.

In addition to graphical presentations, 95-per-cent confidence intervals are used to present re-sults. The medians and 95-percent confidenceintervals for the results of the three foregoing sam-ple studies and the combination are as follows:

Outcomes considered important to patientsreceiving treatment for nephrolithiasis were ana-lyzed in such fashion. In some cases, surrogatesfor patient outcomes were analyzed for example,stone-free rate as a surrogate for symptom im-provement. Evidence from all studies meetinginclusion criteria that reported a certain outcomewere combined within each treatment modality.

Graphs showing the combined results for each

modality are also presented as an estimate of thedifference between the modalities.

With regard to certain outcomes, more data havebeen reported for one or another treatment modali-ty. This results in a sharper and narrower peak inthe graph reflecting the available data. However,

the probability for certain outcomes can vary wide-ly from study to study within one treatment modal-ity. Such variability will result in a wide, flat com-bined distribution, which reflects considerable un-certainty about the outcome or considerable differ-ences between sites and practitioners.

As mentioned previously, there are few random-ized controlled trials for staghorn stones. Thus, thedifferences seen by comparing studies as done heremay be biased to some degree. For example, dif-ferences in patient selection may have had moreweight in yielding the results shown than the dif-fering effects of the treatment modalities. How-ever, these results reflect the best outcome esti-

mates known at the present time.

Study Median 95% CI

1 .746 .536 - .898

2 .750 .722 - .776

3 .667 .628 - .703

Combination .716 .687 - .743


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BACKGROUNDStaghorn calculi are stones that fill the major

part of the collecting system. Typically, suchstones will occupy the renal pelvis, and branchesof the stone will extend into the majority of thecalices. The term partial staghorn is often usedwhen a lesser portion of the collecting system isoccupied by stone. There is, unfortunately, noagreement on how these terms should be defined,and the term staghorn is often used irrespectiveof the percentage of the collecting system occu-

pied.There is also no widely accepted way to expressthe size of a staghorn calculus. As a result, stonesof widely different volumes are all referred to asstaghorns. Staghorn calculi are usually made of struvite (magnesium ammonium phosphate) withvariable amounts of calcium, but stones made of cystine, calcium oxalate monohydrate, and uricacid can all fill the collecting system. Such stonesare frequently found intermixed with struvite cal-culi in many series reported in the literature.

The majority of staghorn stones are composedof struvite. These stones tend to be soft, and theirradiologic appearance varies from relatively faintto moderately radiopaque. It is generally possibleto predict on the basis of a plain x-ray film that astaghorn stone is composed of struvite.

These stones are also called infected stones orinfection stones because they occur only in thepresence of urinary tract infection and only whenthe infection is secondary to organisms that elabo-rate the enzyme urease, which splits urea [Bruceand Griffith, 1981]. Cultures of pieces of struvitestones, taken both from the surface and frominside, have demonstrated that bacteria reside

inside the stones and that the stones themselves areinfected in contrast to stones made of cystine,calcium oxalate monohydrate, or other substances[Nemoy and Stamey, 1971].

An untreated struvite staghorn calculus will intime destroy the kidney, and the stone has a signifi-cant chance of causing the death of the affectedpatient [Rous and Turner, 1977; Koga, Arakai,Matsuoka, et al., 1991]. Moreover, struvite stonesmust be removed in their entirety to be certain of

eradicating all of the infected stone material. If allof the infected material is not removed, the patientwill continue to have recurrent urinary tract infec-tions and the stone will eventually regrow. It maybe possible to sterilize small amounts of struvite,but how much of the stone can be sterilized isuncertain and unpredictable [Pode, Lenkovsky,Shapiro, et al., 1988; Michaels and Fowler, 1991].

TREATMENT METHODSFour modalities reported in the literature are

acceptable as potential alternatives for treatingpatients with struvite staghorn calculi: Open surgery referring to any method of

open surgical exposure of the kidney andremoval of stones from the collecting system;

Percutaneous nephrolithotomy (PNL);

Extracorporeal shock-wave lithotripsy(SWL); and

Combinations of PNL and SWL.

Open surgery

Open surgical removal of the stone has been theso-called gold-standard, to which all other formsof stone removal have been compared. A varietyof specific operations on the kidney may be per-formed in order to remove a staghorn calculus.Depending on anatomy, a pelviolithotomy, extend-ed pyelotomy, nephrotomy, partial nephrectomy, oreven nephrectomy may all play a role in specificcases. The most common operation performedtoday is anatrophic nephrolithotomy, and this isreflected in the literature over the past 20 years[Assimos, Boyce, Harrison, et al., 1989].

Anatrophic nephrolithotomy is usually per-formed with the patient in the flank position. Astandard flank incision is made and frequently arib is resected. After surgical exposure of the kid-ney, an incision is made lengthwise, bivalving thekidney and exposing the stone. Direct inspectionand the use of intraoperative x-rays demonstratethat the kidney is stone free. The time allowed forremoval of the stone is short, unless the kidney iscooled. The principles of the operation are well

Chapter 2: Staghorn calculi and theirmanagement


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1 0

established, with usual operating times of 3-7hours. If the patient has had previous renalsurgery, the operation may be more difficult[Stubbs, Resnick, and Boyce, 1978].

Hospitalizations of 7-14 days are the rule. In

addition to the usual morbidity associated with anyoperation, flank incisions are painful and probablymore painful than midline abdominal incisions.Many patients complain of numbness, paresthesia,and weakness of the abdominal wall resulting inbulging, which may be unsightly. The averagepostoperative disability is six weeks. This is basedon the fact that a typical incision has regainedabout 80 percent of its preoperative strength bythen, but recent work suggests that months maypass before many patients feel completely normal

[Assimos, Wrenn, Harrison, et al., 1991].Occasionally, the stone has caused enough dam-

age to a kidney that nephrectomy is indicated.Such kidneys reveal the effects of years of chronicinfection, episodes of acute pyelonephritis, andhydronephrosis [Assimos, Boyce, Harrison, et al.,1989].

The development of anatrophic nephrolithotomyand the demonstration that patients with infectedstones could be stone free made an excellent casefor this surgical approach, which became the stan-dard throughout the 1960s and 1970s. In 1994,the incidence of open surgery for the treatment of all stones is about 1-2 percent. Staghorn calculicomprise most of the indications.

The decision in favor of nephrectomy is usuallymade when the contralateral kidney is normal ornearly so, and when there is poor function in theaffected kidney.

Percutaneous stone removal

Percutaneous nephrolithotomy (PNL), whichbecame popular as a primary technique for stoneremoval in the early 1980s (Appendix C, pageC.3), can theoretically be used for all stones. Inpractice, extracorporeal shock-wave lithotripsy(SWL) is used in the majority of situations wherePNL was once employed. Struvite staghorn cal-culi, however, are often best managed by PNLeither as a single technique or in combination withSWL.

The procedure may be divided into two parts,access and stone removal. To achieve percutaneousaccess, the urologist or radiologist places a smallflexible guide wire, under fluoroscopic control,through the patients flank into the kidney anddown the ureter. Care is taken to optimize theapproach to the kidney so that the best approach tothe stone is obtained. Once access is achieved, thetract is dilated to 24-30 F. and the nephroscopeintroduced. Under direct vision, the stone is bro-ken up (usually with an ultrasonic probe) and thepieces removed. One of the characteristics of stru-vite is that the stone is usually soft, and fragmenta-tion with removal of the pieces is often quick.

PNL has unquestioned advantages: (1) If thestone can be seen, it can almost always be des-troyed. (2) The collecting system may be directlyinspected so that small fragments may be identifiedand removed. (3) Because the tract can be keptopen indefinitely, repeated inspections are possible.(4) The process is rapid, with success or lack of itbeing obvious immediately.

Hospitalizations are usually from 4-10 days withmost patients returning to light activity after 1-2weeks. Transfusion rates for PNL in treatingstaghorn calculi vary from 5 to 50 percent. Re-treatment rates that is, the rate at which the in-strument must be reinserted through the tract toremove residual stones vary from 10 percent insimple situations to 40-50 percent for more compli-cated problems. Stone-free rates of 75-90 percentare regularly achievable using PNL.

One disadvantage is that the expertise requiredfor this operation is not as widely available as itonce was, because a greater number of urologytraining programs are focusing less on PNL andmore on shock-wave lithotripsy for stone manage-ment.

Extracorporeal shock-wavelithotripsy

Shock-wave lithotripsy (SWL) has become thestandard method for management of many calculiin the urinary tract (Appendix C, page C.1). SWLis based on the principle that a high-pressure shock wave will release energy when passing throughareas of different acoustic impedance. Shock waves generated outside the body can be focused


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onto a stone using a variety of geometric tech-niques. The shock wave passes through the bodywithout trauma and releases its energy as it passesinto the stone. Hundreds, or sometimes thousands,of such shock waves are required to break up theaverage small stone, with the goal being to reducethe size of the stone to particles small enough topass without significant pain.

There are many different shock-wave machinesavailable today. Although they are based on thesame general principle, there are significant differ-ences that relate to the use of these machines fortreatment of large stones such as staghorn calculi.

The original machine, the Dornier HM-3, proba-bly the most common machine throughout theworld, has the largest focal point and, in its unmod-

ified version, the highest power of all currentdevices. In an effort to reduce the anesthesiarequirement, newer machines often have less powerand smaller focal points. This means that stonestreated with such machines will often require moreprocedures to achieve the same result producedwith fewer procedures by other devices.Obviously, for very large stones, multiple treat-ments may be required.

Shock-wave lithotripsy has few short-term com-plications, its noninvasive nature has much appeal,

and the technique is widely available. SWL hasdisadvantages, however, particularly in regard tothe management of staghorns. The panel found, asstated on pages 14 and 19, a relatively higher risk of residual fragments following initial treatmentand a high probability of unplanned secondary pro-cedures.

Because multiple treatments may be needed, useof SWL may not be practical to provide therequired frequency of service if only mobile SWLis available and ancillary procedures directed

toward the management of fragments are necessary.In addition, although many factors bear on the costof any medical procedure, at the present time SWLis often more expensive than endourology or opensurgery for the same condition [Hatziandreu,Carlson, Mulley, et al., 1990].

Combination PNL and SWLSome stones can be best managed by using both

PNL and SWL on the same stone. This combinesthe main advantage of percutaneous ultrasoniclithotripsy, that of removing rapidly large volumes

of easily accessible stone, with the advantage of SWL in easily treating small volumes of stone thatare difficult or dangerous to access using PNL.

The surgeon first utilizes PNL, making everyeffort to remove as much stone as possible, beforeusing SWL. Experience has demonstrated that fol-lowing SWL, the passage of fragments cannot bepredicted. Therefore, depending upon the extentand location of residual stones, repeat SWL and/orrepeat PNL may be necessary to remove residualfragments.

Ancillary proceduresPercutaneous nephrostomy tube placement

(PNTP) may be necessary at any point in the man-agement of staghorn stones. It is a routine part of PNL, of course, and is frequently used after SWLfor drainage of an infected stone and for pain relief when obstruction is present. Preliminary stent in-sertion prior to SWL for staghorn calculi is socommon as to be part of the procedure. Frequentlya double-pigtail stent is placed and left indwelling

for days or weeks to maintain drainage while frag-ments pass.

Irrigations of the collecting system with solu-tions such as Renacidin to dissolve remaining frag-ments of infected stones, particularly after PNL,have been advocated by some. This is not a com-mon procedure, probably because it often meansadded hospitalization. The panel did not find suffi-cient evidence in the literature to support the use of Renacidin as a primary procedure for treating in-fected stones.

Ureteroscopy may be needed to remove frag-ments too large to pass spontaneously. General orregional anesthesia is necessary, but success ratesare very high (95 percent or greater). Most often,ureteroscopy is an outpatient procedure.

1 1


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1 2

DIRECT AND INDIRECT OUTCOMESAny therapeutic medical intervention has a cer-

tain set of outcomes, some of which are desirable(benefits) and some of which are not (harms)[Eddy, 1990]. Direct health outcomes are thosefelt directly by the patient and have an impact onthe quantity or quality of life. Indirect biologicoutcomes are physiologic end points such as ab-sence of infection or incidence of stone recurrence.These may be of great importance to the clinicalresearcher. Also, physicians, in general, believe

that outcomes such as absence of residual stones,prevention of stone recurrence, and limitation of residual stone growth are of the greatest impor-tance when assessing treatment options forstaghorn calculi, although patients may not viewthese outcomes per se as important end points.

An example of the difference between the twotypes of outcomes is illustrated by the patient witha recent myocardial infarction. Although the levelof the CPK enzyme is an important parameter forthe physician (indirect biologic outcome), it cannotbe felt by the patient in any way. Meanwhile, thechest pain or death associated with the infarctionhas an immediate impact on the patients quality orquantity of life (direct health outcome).

Similarly, in treatment of staghorn calculi, thepatient may not be interested in the stone-free rate,the chance of developing recurrent stones, or theincidence of growth of residual calculi followingstone removal, despite the critical importance of these parameters to the physician unless the im-plications of the parameters are explained to thepatient.

However, the patient will very likely be interest-ed in direct outcomes such as the degree of symp-

tom improvement after treatment, the complica-tions or side effects of treatment, mortality, and thecost and duration of hospital stay. For patients toparticipate in a shared decision-making processregarding treatment, they must be fully aware notonly of the magnitude of the direct outcomes relat-ed to treatment alternatives, but also of the rangeof uncertainty associated with these outcomes.

Indirect biologic outcomes can occasionallyserve as proxies for direct health outcomes. The

incidence of infection may serve as a proxy for thedegree of symptom improvement after treatment,and stone-free rate is used as a proxy for stonerecurrence and symptom recurrence because thesedata are not available in the current literature.

COMBINING OUTCOME EVIDENCEThe panel conducted a comprehensive review of

the English-language literature and combined alloutcome evidence for given treatment options, uti-lizing the confidence profile method as described

on pages 6-8 of Chapter 1. The results of the com-bined review are presented in the balance sheettable on page 13.

Outcomes with a wide confidence interval in-dicate considerable uncertainty in the medicalknowledge base. This uncertainty is due either toa limited number of studies reported for a givenintervention (as is the case for combination thera-py) or to a wide variation in outcome probabilityreported in different studies (as is the case forshock-wave lithotripsy therapy). The short dura-tion of many studies introduces uncertainty aswell.

The combined analysis is also weakened by thequality of the individual studies. As noted previ-ously, there are currently few randomized, pro-spective controlled studies of staghorn calculi ther-apy in the literature. Therefore, most of the dataanalyzed by the panel come from clinical series.The limitations of including these types of studiesare obvious. Nevertheless, if clinical series werenot included, nothing could be said about the bene-fits and harms of various types of surgical removalof staghorn calculi.

Further limitations arise from differences in

study populations. In many cases, it is likely thatpatients who are entered into trials of alternativetherapies have less severe disease states than thoseundergoing surgery. Moreover, the definition of staghorn calculi may differ significantly amongvarious investigators, and some of the reports re-garding the management of staghorn calculi do notspecify the size of the stones or portion of the col-lecting system occupied. Thus, not all studies maybe comparing treatment outcomes of stones of sim-

Chapter 3: Outcomes analysis for staghorntreatment alternatives


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1 3

ilar size, composition, or location within the kid-ney. In these cases, the panel attempted to extrap-olate from existing information to equate the treat-ment outcomes.

Despite such limitations, the panel is reasonablycertain that the confidence intervals contain the

true probability of a given outcome for mostsites. Better estimates, narrower confidence inter-vals, and greater certainty about treatment differ-ences can be obtained through large, well-con-trolled studies that test the different therapies in thesame patient population. However, until thesetypes of outcome studies are completed, guidancecan still be given to the physicians and patientswho are forced to make decisions at the presenttime.

THE BALANCE SHEETThe balance sheet table details the results of an

exhaustive combined analysis of the staghorn cal-culi treatment literature. In most cases, a 95-per-cent confidence interval is reported along with themedian probability. This median both as givenin the balance sheet and as referred to in the out-come analysis discussion that follows is themedian of the probability distribution resultingfrom the meta-analysis of outcome data. It is not

the median of an array of individual study results.In some cases, combined analysis could not be per-formed because of the way outcomes were report-ed in the literature.

ANALYSIS OF THEBALANCE SHEET OUTCOMES

The following sections discuss in detail theanalysis used to generate the data on the balancesheet. The information is organized in relation tooutcomes listed on the left side of the balancesheet, beginning with stone-free rate. Tables inaddition to those from Appendix A (A-1 - A-21),referenced in this chapter, are contained in theTechnical Supplement available upon request.These additional tables include FAST*PRO analy-sis tables.

Stone-free rateTo assess successful outcomes following vari-

ous modalities of stone removal, one can deter-mine the resolution of symptoms, absence of infec-tion, or inhibition of recurrent stone formation orstone growth. However, most urologists wouldagree that the stone-free rate following stone re-moval is the most quantifiable and meaningfuldeterminant of successful treatment.

Balance sheet: outcomes of treatments for staghorn kidney stones

Combined SWL andPercutaneous Percutaneous

Outcomes SWL Nephrolithotomy Nephrolithotomy Open SurgeryStone-free rate:

Median 0.500 0.733 0.808 0.81695% confidence interval 0.256-0.744 0.547-0.874 0.678-0.905 0.566-0.957

Acute complications:Overall significant complications:*

Median 0.308 0.074 0.244 0.11995% confidence interval 0.022-0.816 0.003-0.322 0.039-0.611 0.006-0.465

Transfusion:Median 0.009 0.108 0.120 0.08995% confidence interval 0.002-0.022 0.003-0.478 0.052-0.222 0.078-0.101

Death:Median 0.0007 0.001 0.002 0.00695% confidence interval 0.00006-0.003 0.0001-0.005 0.0001-0.006 0.004-0.009

Procedures/pt.:Primary 2.122 1.486 2.768 1.026Secondary 0.424 0.047 0.034 0.002

Long-term complications:Stone recurrence:

Median 0.058 0.068 No data 0.12095% confidence interval 0.016-0.161 0.015-0.176 0.036-0.269

Stone growth:Median No data 0.070 No data 0.08395% confidence interval 0.026-0.142 0.030-0.171

Renal impairment:Median No data No data No data 0.06395% confidence interval 0.021-0.138

Loss of kidney:Median No data 0.016 No data 0.03795% confidence interval 0.001-0.061 0.011-0.086

No. hospital days 8.72 10.09 12.73 10.99* Hydrothorax, pneumothorax, perirenal hematoma, vascular injury, urinoma, secondary unplanned interventions, sepsis, loss of kidney.


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1 4

Much of the literature regarding stone-free ratehas been clouded in the age of shock-wave litho-tripsy by studies that include patients with smallresidual fragments (so-called clinically insignifi-cant residual fragments) together with patientswho are truly stone free. Also, the method of

assessing the stone-free state has a significantimpact on the number of patients who are free of stones following surgery.

Several studies evaluating different methods of assessing stone-free status conclude that a plainabdominal radiograph (KUB) may significantlyunderestimate the incidence of residual fragments,as compared to plain renal tomograms or ultrason-ography [Denstedt, Clayman, and Picus, 1991;Jewett, Bombardier, Caron, et al., 1992]. Directvision nephroscopy has the highest sensitivity ratefor assessing stone-free status, but it is the mostinvasive method of residual stone determination.The majority of the studies included in the presentanalysis utilized only a plain abdominal radiographto assess residual fragments. Therefore, the stone-free figures are probably overestimated.

A total of 26 studies utilizing SWL monotherapyto manage staghorn calculi were analyzed, repre-senting a total of 1,669 patients or renal units. Themedian stone-free rate for this group was 0.50(95% CI 0.256 - 0.744). The studies included inthe analysis are listed in Table A-2, Appendix A.

The type of SWL machine may impact thestone-free rates for staghorn calculi. The higher-

powered lithotripters (the electrohydraulic DornierHM-3 and the electromagnetic Siemens Lithostar)impart significantly more energy to fragment thestones than do the piezoelectric devices (Wolf 2300and EDAP). Although only data from two piezo-electric machines are included in this analysis, theirstone-free rates appear to be significantly lowerthan those reported for the other lithotripsy devices(Table A-2).

The stone-free data for PNL monotherapy arelisted in Table A-3 and represent a total of 14 stud-ies in 511 renal units. The FAST*PRO analysis

calculated the median stone-free rate at 0.733 (95%CI 0.547 - 0.874).The stone-free rates for combination percuta-

neous stone removal and shock-wave lithotripsytreatment of staghorn calculi are listed in TableA-4. This group represents five studies reportingon 796 patients. The stone-free rate for the groupwas 0.808 (95% CI 0.678 - 0.905) usingFAST*PRO analysis.

Thirty-one studies reported stone-free rates in2,487 patients using open surgical techniques

(Table A-5). It should be noted that the open surgi-cal procedures included simple pyelolithotomy,extended pyelolithotomy, combination pyelolithoto-my with radial nephrotomies, as well as a formalanatrophic nephrolithotomy. Analysis of thesestudies revealed a median stone-free rate of 0.816

(95% CI 0.566 - 0.957) using FAST*PRO.Comparative analysis using the FAST*PRO pro-gram for the four different surgical modes of stoneremoval is represented in Figure 4. The findingsdemonstrate, not surprisingly, that stone-free ratesincrease as the invasiveness of the surgical proce-dure increases. If, indeed, stone-free figures areused to ultimately decide the most appropriatemode of stone removal, open surgery should pro-vide the best results. Moreover, this comparativeanalysis should demonstrate to the patient that al-though shock-wave lithotripsy monotherapy mightbe the least morbid of the surgical modalities, itdefinitely provides the lowest stone-free rates of the available treatment options.

Acute complicationsThe data abstraction sheet (Appendix B) lists a

number of acute complications. They include per-foration of the renal pelvis, hydrothorax/pneumo-thorax, perirenal hematoma, significant blood loss,

vascular injury, transfusion, urinoma, sepsis, stentmigration, renal impairment, wound infection, lossof kidney, and death. Secondary, unplanned inter-ventions were also considered by the panel to beacute complications.

In reviewing all studies for which there weredata regarding acute complications, it became ob-vious to the panel that three major acute complica-tions would most concern the patient as well as thephysician: (1) the need for secondary, unplannedinterventions, (2) the need for transfusion, and

Figure 4. Staghorn stone-free rates

Probability


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1 5

(3) death. Data for these three major complica-tions are listed separately in Appendix A (TablesA-6, A-7, A-8, and A-9). Secondary, unplannedinterventions were not analyzed by FAST*PROseparately, but were combined with other acutecomplications for inclusion in the balance sheet

under Overall Significant Complications.Transfusion and death were analyzed byFAST*PRO separately, and median probabilitiesand 95-percent confidence intervals for these twooutcomes appear separately on the balance sheet.

Table A-6 gives the acute-complications data forshock-wave lithotripsy monotherapy used to treatstaghorn calculi. The FAST*PRO analysis shows,for overall significant complications in patients un-dergoing SWL monotherapy for staghorn calculi, arelatively high median rate of 0.308 (95% CI 0.022- 0.816). A major contributor to this high overallrate was the high percentage of secondary, un-planned interventions shown in Table A-6. Themedian transfusion rate for SWL monotherapy was0.009 (95% CI 0.002 - 0.022).

The percentage of deaths following SWL mono-therapy, when initially assessed, was found to be0.13 percent. This mortality rate was based on onereported death in a population of 771 patients forwhom acute complications were reported (TableA-6). The panel believed that the resulting per-centage was clinically too high and that the reasonmay have been that many studies of SWL mono-therapy for staghorn stones did not report acute

complications, thereby lowering the denominatorused in the calculation.The mortality rate was recalculated using a

patient denominator of all patients undergoingSWL monotherapy for staghorn calculi (1,681 pa-tients), rather than only those for whom acute com-plications were reported. (The panel assumed thatif a patient had died during any clinical study of SWL monotherapy to treat staghorn calculi, thedeath would surely have been reported.) The recal-culation dropped the mortality rate to 0.06 percent,which is more consistent with the panels percep-tion of mortality from SWL monotherapy. FAST*

PRO analysis of mortality for the balance sheetproduced a median of 0.0007 (95% CI 0.00006 -0.003).

For PNL monotherapy of staghorn calculi (11studies, 921 patients), the median rate for overallsignificant complications was 0.074 (95% CI 0.003- 0.322). Listings in Appendix A are in Table A-7.

There were seven secondary, unplanned inter-ventions in the total of 921 PNL patients (TableA-7), making the percentage of secondary, un-

planned interventions for this percutaneous groupsignificantly less than for SWL monotherapy. Themedian transfusion rate for PNL, however, was0.108 (95% CI 0.003 - 0.478), significantly higherthan for SWL. The median mortality rate for PNLwas also much higher at .0011 (95% CI .0001 -

.0045).The data suggest that the more invasive percuta-neous procedure results in higher transfusion anddeath rates than SWL monotherapy does. Thenumber of secondary, unplanned interventions,however, was significantly higher in the SWLgroup, which suggests problems with incompletestone removal secondary to SWL.

The panel analyzed five studies that utilizedcombination percutaneous and shock-wave litho-tripsy treatment for staghorn calculi. For the 781patients represented, where data for acute compli-cations were available, the percentage of overallsignificant complications was 23.94 percent (TableA-8). This included a secondary, unplanned inter-vention rate of 1.62 percent.

FAST*PRO analysis of data from the combina-tion PNL-SWL group yielded the following bal-ance-sheet estimates: for overall significant com-plications, a median rate of 0.244 (95% CI 0.039 -0.611); for transfusion, a median rate of 0.120(95% CI 0.052 - 0.222); for mortality, a medianrate of 0.002 (95% CI 0.0001 - 0.006).

Acute complications were reported in 27 studiesof open surgery for staghorn calculi, representing

2,314 patients. Of these 2,314 patients, 27.53 per-cent experienced overall significant complications(Table A-9), of which 0.30 percent represented sec-ondary, unplanned interventions. The FAST*PROanalysis yielded a median rate of 0.119 (95% CI0.006 - 0.465) for overall significant complicationsfollowing open surgery for staghorns. The mediantransfusion rate was 0.089 (95% CI 0.078 - 0.101),and the median rate for mortality was 0.006 (95%CI 0.004 - 0.009).

Acute-complications data overall for the fourmodalities of stone removal show the more invasivemodalities, such as open surgery and percutaneousstone removal, with higher rates of transfusion anddeath than the rates for the less invasive therapy of shock-wave lithotripsy. However, as noted previ-ously, shock-wave lithotripsy monotherapy of staghorn calculi was followed by many more sec-ondary, unplanned interventions. The panelbelieves that this is a significant finding since thesesecondary, unplanned interventions resulted inincreased patient morbidity as well as increasedcost for stone removal. Figures 5-7 display


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1 6

FAST*PRO graphical analyses comparing the fourmodalities with regard to overall significant com-plications, transfusions, and death.

Procedures per patient(primary and secondary)

An important outcome on the balance sheet, incomparing the various surgical modes of staghornstone removal, analyzes the number of proceduresperformed per patient to achieve a successful re-sult. Before 1979, when open surgery was the onlymodality available to treat struvite staghorn calculi,it was unusual to perform more than one procedureper patient to remove all stone material. However,in an age of less invasive techniques for stone re-moval, the need for repeat primary and, in somecases, secondary procedures has significantly in-creased in order to attempt complete removal of thestone material.

A total of 16 studies using SWL monotherapywere available for analysis, representing 835 pa-tients. These individuals underwent 1,772 primary

SWL procedures, 2.12 per patient (Table A-10). Intotal, the 835 SWL patients underwent 2,126 pro-cedures, which represented an additional 0.42 sec-ondary procedures per patient (Table A-10). Thus,the advantage of reduced invasiveness for SWLtherapy for staghorn calculi resulted in a total of 2.55 procedures per patient including both prima-ry and secondary SWL procedures as well asadditional procedures which included percutaneousnephrostomy tube placement, ureteroscopy, and insome cases open surgery. Twenty-three studies thatreported SWL monotherapy of staghorn stoneswere not included in this analysis of procedures per

patient because they reported on less than five pa-tients or did not contain specific information onnumbers of procedures per patient.

In the PNL group, 10 studies met entrance crite-ria. They represent a total of 854 patients. Thesepatients underwent 1,269 primary percutaneousstone removal procedures, for a primary procedurerate of 1.49 per patient. The 854 patients under-went a total of 1,309 procedures, including an addi-tional 0.05 secondary procedures per patient (TableA-11). The total procedures-per-patient rate of 1.53 was significantly less than the total proce-dures-per-patient rate of 2.55 seen with the SWLmonotherapy group. Ten additional PNL studieswere not included in this analysis because no spe-cific data were presented regarding the number of procedures per patient or because the study samplewas less than five patients.

In the combination therapy group, six studiesmet entrance criteria, representing 168 patients(Table A-12). These patients underwent a total of 222 percutaneous procedures and 243 SWL proce-dures, representing a 2.77 primary procedures-per-

Figure 5. Overall significant complications: Comparison ofmodalities

Probability

Figure 7. Death: Comparison of modalities

Probability

Figure 6. Transfusions: Comparison of modalities

Probability


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patient rate. By definition, in the combination ther-apy group, which includes management of thestaghorn stone by both percutaneous and shock-wave lithotripsy, the minimum procedures-per-patient rate would be 2.0. An additional 0.03 pro-cedures per patient were performed in the combina-

tion group, yielding a total procedures-per-patientrate of 2.80 (Table A-12).As one would expect, the number of procedures

per patient in the open surgery group was the low-est of all four modalities for stone removal. TableA-13 presents the 27 studies. They represent 1,672procedures on 1,630 patients for a primary proce-dure rate of 1.03 per patient. With secondary pro-cedures, a total of 1,676 procedures were per-formed in this group of patients. The total proce-dures-per-patient rate remained at 1.03 (roundedoff), as the number of additional procedures perpatient was only 0.002.

Most series of open surgery were reportedbefore 1980, prior to the availability of percuta-neous surgery and shock-wave lithotripsy. Thisexplains the low secondary procedure rate, reflect-ing reluctance of the surgeon and the patient torepeat open surgical procedures. Twenty-five stud-ies were excluded from the analysis of proceduresper patient in the open group because there werefewer than five patients or because of not providingspecific data regarding the numbers of proceduresper patient.

Long-term complicationsThe long-term complications reported for the

four modes of stone removal included stone recur-rence, stone growth, renal impairment, and loss of kidney following surgery. Unfortunately, only asmall amount of data was available from the stud-ies analyzed regarding these long-term complica-tions. Only one SWL monotherapy study reportedstone recurrence in 3 of their 54 patients (TableA-14), yielding a FAST*PRO median recurrentstone rate of 0.058 (95% CI 0.016 - 0.161).

Analysis of the percutaneous monotherapygroup of studies (Table A-15), also with a limitednumber of patients (93), yielded a median rate of stone recurrence of 0.068 (95% CI 0.015 - 0.l76) aswell as a median rate of stone growth of 0.070(95% CI 0.026 - 0.142). One of the 93 patients inthe PNL group had a long-term complication of renal loss.

A significant amount of information was re-ported in the studies of open surgery, with data on1,549 patients for whom long-term complicationswere noted (Table A-16). FAST*PRO analysis of the open group yielded a higher median stone

recurrence rate, 0.120 (95% CI 0.036 - 0.269), thanthe median rates for the SWL and PNL groups. Asmall number of patients in the open group werefound to have growth of their residual stones,yielding a median stone growth rate of 0.083 (95%CI 0.030 - 0.171). Renal impairment during long-

term follow-up was a median 0.063 (95% CI 0.021- 0.138), and 21 of the 1,549 patients eventuallylost a kidney (Table A-16).

No data on long-term complications were report-ed for the combination PNL-SWL group. It shouldbe noted that renal impairment or loss of kidneymay not necessarily be due directly to stone remov-al, but may be secondary to other factors.

It appears that the open surgery group had thehighest rate of stone recurrence, but in comparisonwith very scanty data presented for the SWL andPNL series. The discrepancy is probably due to thefact that a larger number of open studies haveinvestigated the long-term results of this form of stone removal. SWL and PNL studies, for themost part, have only reported short-term follow-up.The panel anticipates that, if followed long enough,the PNL, SWL, and combination groups will showrates of stone recurrence and growth similar to

1 7

Figure 8. Stone recurrence: All modalities combined

Probability

Figure 9. Stone growth: All modalities combined

Probability


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1 8

those in the open series. One would not expectthe mode of stone removal to have any effect on apatients propensity for recurrent stone formationor growth of residual stone fragments. Medianrates for long-term complications are graphed inFigures 8-10.

Hospital daysAny form of surgical stone removal for staghorn

calculi, including the least invasive option of shock-wave lithotripsy, may require patient hospi-talization. The data on hospital days was directlyextracted from the literature and included in thebalance sheet. In the case of SWL and of combi-nation therapy, the total hospitalization may notrepresent continuous stay within the hospital. Forexample, the patient might have been hospitalizedfor 1-3 days the first time, discharged, and thenreadmitted for a second or third treatment. Thehospital days represent a cumulative total of thereported hospital stay for each modality.

Hospitalization practices vary from country tocountry and change over time. No attempt wasmade to correct for varying practices of this type.All of the hospital data are somewhat exaggeratedby current standards.

For patients with staghorn calculi undergoingSWL monotherapy, a total of seven studies, repre-

senting 305 patients and 2,660 hospital days, metappropriate criteria and were included for analysis(Table A-17). An additional 30 studies wereexcluded because they did not meet appropriatecriteria for analysis. They either did not reporthospital days or reported less than five patients.

Six studies, representing 247 patients who hadundergone percutaneous monotherapy for staghornstones, and representing 2,493 days, met analysiscriteria and are listed in Table A-18. Fourteenstudies of percutaneous monotherapy were exclud-ed from analysis due either to low numbers of pa-tients or to nonreporting of hospitalization.

Table A-19 defines the five studies utilizingcombination shock-wave lithotripsy and percuta-neous stone removal for the management of stag-horn stones in 775 patients, for a total of 9,869hospital days. One combination study was ex-

cluded from analysis due to nonreporting of hospi-talization.

Of the patients with staghorn calculi treatedwith open surgery, nine studies met entrance crite-ria for analysis, representing 1,354 patients and14,886 patient days (Table A-20). In 42 studieswhere patients had undergone open therapy forstaghorn calculi, hospitalization data were not pre-sented and could not be analyzed.

Hospitalization was highest for the combinationtherapy groups (12.73 hospital days), probably dueto the increased number of procedures performed

on each patient. Although the hospitalization datafor the shock-wave lithotripsy monotherapy groupseem somewhat high at 8.72 hospital days, itshould be noted that these were complex staghorncalculi being treated with shock-wave monothera-py with an average of approximately 2.5 proce-dures per patient.

Moreover, five of the seven studies included inthe SWL monotherapy group were performed out-side the U. S. (Table A-21), where there is less in-centive to minimize hospitalization than in theU. S. health care system.

Figure 10. Loss of kidney: All modalities combined

Probability


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There are five methods of managing staghorn

calculi. One is by watchful waiting (observation).The other four are the active treatment modalitiesdescribed in Chapter 2 and in greater detail inAppendix C. They are (1) open surgery, (2) percu-taneous nephrolithotomy (PNL), (3) extracorporealshock-wave lithotripsy (SWL), and (4) combina-tions of PNL and SWL.

The panels recommendations regarding use of these modalities to treat struvite staghorn calculiare based on the outcomes analysis presented indetail in Chapter 3.

TREATMENT OUTCOMES ANDTREATMENT RECOMMENDATIONS

The panel concluded, from reviewing the litera-ture and analyzing the data, that the following out-come probabilities are the most significant in set-ting forth recommendations for treatment of stru-vite staghorn calculi:

The probability of being stone free followingtreatment;

The probability of undergoing secondary,unplanned procedures; and

The probability of having complications associ-ated with the chosen primary treatment modality.The four modalities of open surgery, PNL, SWL,

and combination PNL and SWL are all reasonabletreatment alternatives for patients with struvitestaghorn calculi. However, outcome probabilitiesdiffer markedly among the four. The followingstatements are based on both statistical analysis of abstracted data from the treatment literature andexpert opinion. They form the basis of the panelsrecommendations:

The risk of having residual fragments followinginitial treatment is clearly higher after shock-wavelithotripsy monotherapy than after percutaneousnephrolithotomy, combination therapy, or opensurgery.

It is the expert opinion of the panel that residualfragments of infected calculi left in the renal col-lecting system may be associated with recurrentinfections and eventual regrowth of these fragmentsinto significant stones leading to additional morbid-ity, although literature to support this opinion isscarce.

Shock-wave lithotripsy monotherapy carries a

high probability of unplanned secondary proce-dures.Percutaneous nephrolithotomy, combination

therapy, and open surgery are more likely torequire general or regional anesthesia.

The chance that a blood transfusion will berequired is greater for percutaneous nephrolithoto-my, combination therapy, and open surgery than forshock-wave lithotripsy monotherapy.

Rates of complications following the four treat-ment modalities differ significantly for each modal-ity. From the patients viewpoint, a complication

may have the same importance as a secondary,unplanned procedure, inasmuch as it may require asecond anesthetic procedure or prolong thepatients hospital stay. Therefore, an analysis com-bining secondary, unplanned procedures and thecomplications associated with the primary treat-ment modalities chosen may accurately reflect thepatients viewpoint regarding desirability or unde-sirability of a given intervention.

Of all four treatment modalities, shock-wavelithotripsy monotherapy has the highest combinedcomplication and secondary, unplanned interven-tion rate. However, the complications associatedwith shock-wave lithotripsy monotherapy tend tobe less severe than those associated with percuta-neous nephrolithotomy, combination therapy, oropen surgery.

The peer-reviewed literature does not stratifyoutcomes appropriately by either size or composi-tion of staghorn calculi or the anatomy of the col-lecting system. Nevertheless, the panel believesthat these factors impact the outcomes of alterna-tive treatment procedures.

Also, when choosing a treatment alternative,special circumstances such as the patients overall

health, body habitus, and other medical problemsneed to be taken into consideration by the treatingphysician.

THE PATIENTPanel recommendations for the treatment of

staghorn calculi apply to standard and nonstandardpatients whose stones are presumed to be com-posed of struvite (magnesium ammonium phos-phate).

1 9

Chapter 4: Staghorn treatment recommendations


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2 0

A standard patient is defined as an adultpatient who has two functioning kidneys (functionof both kidneys relatively equal) or a solitary kid-ney with substantially normal function, and whoseoverall medical condition, body habitus, and anato-my permit performance of any of the four accepted

active treatment modalities including use of anes-thesia.A nonstandard patient is defined as one with

a struvite staghorn stone who does not fulfill theabove criteria. For this patient, the choice of avail-able treatment options may be limited to three oreven fewer of the four accepted active treatmentmodalities, depending on individual circumstances.

The standards and guidelines recommended bythe panel apply to the treatment of standard pa-tients, followed by options for nonstandard pa-tients.

The terms standards, guidelines, and options, asused in the panels recommendations, refer to thethree levels of flexibility for treatment policies. Astandard is the least flexible of the three, a guide-line more flexible, and an option the most flexible.

RECOMMENDATIONS : S TANDARDS1. As a standard, a newly diagnosed struvite

staghorn calculus represents an indication foractive treatment intervention. Although this rec-ommendation was not formally subjected to dataabstracting and statistical methods, the panel

strongly believes based on expert opinion that apolicy of watchful waiting and observation is notin the best interest of the standard patient withstruvite staghorn calculi.In previous years, some physicians thought that

patients with staghorn stones were better leftuntreated, without efforts to remove the stone[Libertino, Newman, Lytton, et al., 1971]. Thisidea was based on the concept that staghorn calculiwere likely to be asymptomatic except for bacteri-uria and that if symptoms were few, it was hard to

justify the aggressive surgical procedures necessary

to render the patient stone free. Review of the lit-erature, however, reveals that few patients do wellwithout the removal of their stones [Rous andTurner, 1977].

At the Mayo Clinic, the histories of 382 patientswith staghorn calculi were reviewed [Priestly andDunn, 1949]. Two hundred and thirty-four patientshad only a unilateral staghorn calculus. In thesepatients, the survival rate was only 41 percent for

those treated with observation alone compared to81 percent for those who underwent nephrolithoto-my.

Another study [Blandy and Singh, 1976]reviewed a group of 185 patients with staghorn cal-culi. Sixty of these patients were treated with ob-

servation alone, and 125 had surgical removal of their stones. The operated group had a 7.2-percentmortality rate over a 10-year period, but 28 percentof those in the observation-only group died overthat period. Significant hydronephrosis was notedin another 15 percent.

In a recent study of 167 patients, 61 of whomwere followed for an average of nearly eight years,one-third had chronic renal failure secondary tobilateral staghorn stones and seven died of uremia[Koga, Arakaki, Matsuoka, et al., 1991]. Twenty-five percent had nephrectomy revealing changes of hydronephrosis, abscess, and pyelonephritis.

It is clear that left untreated, a struvite staghornwill eventually destroy the kidney. Patients willusually have recurrent urinary tract infections,episodes of sepsis, and pain. Also, the stone has asignificant chance of causing death in the affectedpatients. Nonsurgical treatment, that is, manage-ment with antibiotics and supportive measuresonly, is not considered a viable option except inthose patients otherwise too ill to tolerate stoneremoval.

2. As a standard, a patient with a newly diagnosedstruvite staghorn calculus must be informedabout the four accepted active treatment modali-ties, including the relative benefits and risksassociated with each of these treatments.Although, as a practical matter, it is evident that

the availability of equipment and the expertise of an individual practitioner may impact the choice of a treatment intervention, it is unacceptable to with-hold certain treatments from the patient and notoffer them as alternatives because of personal inex-perience or unfamiliarity with one of the acceptedtreatment modalities, or because of the localunavailability of equipment or expertise.

RECOMMENDATIONS : G UIDELINES1. As a guideline, percutaneous stone removal, fol-

lowed by shock-wave lithotripsy and/or repeatpercutaneous procedures as warranted, should beutilized for most standard patients with struvitestaghorn calculi, with percutaneous lithotripsybeing the first part of the combination therapy.


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2. As a guideline, shock-wave lithotripsy mono-therapy should not be used for most standardpatients as a first-line treatment choice.

3. As a guideline, open surgery (nephrolithotomyby any method) should not be used for moststandard patients as a first-line treatment choice.

RECOMMENDATIONS : O PTIONS1. As options, shock-wave lithotripsy monotherapy

and percutaneous lithotripsy monotherapy areequally effective treatment choices for small-volume struvite staghorn calculi in collectingsystems which are of normal or near normalanatomy.

2. As an option, open surgery is an appropriatetreatment alternative in unusual situations wherea staghorn calculus is not expected to be remov-

able by a reasonable number of percutaneouslithotripsy and/or shock-wave lithotripsy proce-dures.

3. As an option for a patient with a poorly func-tioning, stone-bearing kidney, nephrectomy is areasonable treatment alternative.

RECOMMENDATION LIMITATIONSLimitations to the process of developing treat-

ment recommendations became apparent during thepanels review of the literature. Most obviously,

for the purpose of this document, there is no uni-form system of categorizing staghorn calculi, nostandard method of describing the collecting sys-tem, and no widely accepted system of reportingthe size of staghorn calculi.

Few prospective, randomized, controlled studieshave been conducted concerning the treatment of struvite staghorn calculi. In addition, there is nouniform system in the literature for reporting out-comes following treatment for struvite staghorncalculi.

Further uncertainty stems from differences inhealth care delivery systems in various countries asthey impact the outcomes reported in the literature.Variability in the data leads to uncertainty in out-come estimates, which leads to flexibility in rec-ommendations. This limitation applies to a varietyof outcomes.

Also, in most of the papers reviewed for thisdocument, the unmodified Dornier HM-3 was used

for shock-wave lithotripsy. Future studies in whichother machines are used, as monotherapy or incombination with other modalities, could changethe results of treatment requirements.

Notwithstanding these limitations, the panelbelieves that the standards, guidelines, and options

presented are well supported by the data reviewed.Recommendations are founded primarily on thedata and partially on the expert opinion of panelmembers. Outcomes for which there is consider-able uncertainty are clearly identified as such in thedocument. Whenever the panels expert opinionprevailed over the limited amount of available data,this is specified in the document as well.

Panel recommendations are made with theknowledge that they have not undergone review bythe public. Further, the panel acknowledges thatalthough issues of expense may have a bearing ontreatment choices, the panel is unable to addressthis aspect of the problem at the present time.Moreover, to date, no patient preference analysishas been performed to validate the recommenda-tions of the panel. Rather, the panel acted aspatient advocate and recommended treatmentchoices based on the balance sheet while acting asa proxy patient. The panel realizes that thismethod is less than ideal and may not reflect thethinking of actual patients, but it is currently themethod most available to formulate treatment rec-ommendations.

BASIC RESEARCH NEEDSFour basic improvements are needed to build a

more solid foundation for future research onstaghorn calculi:

1. A consistent method of classifying staghorn cal-culi needs to be devised, including an acceptedsystem for reporting size.

2. A consistent method of describing the collectingsystem also needs to be devised.

3. Uniform methods of reporting outcomes areneeded. For example, in reporting stone-freerates, distinctions need to be made betweenstone free and stone free with insignificantresidual fragments.

4. Parameters need to be established for stratifyingstudy results in terms of demographic data forexample, in terms of a study populations sizeand composition.

2 1


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2 2

1. * Alken P, Throff, JW, Hammer, C. The use of operative ultra-sonography for the localization of renal calculi. World Journal of Surgery 1987;11:586-92.

2. Alken, P. Percutaneous ultrasonic destruction of renal calculi.Urol Clin North Am 1982;9:145-51.

3. * Androulakakis PA, Michael V, Polychronopoulou S,Aghioutantis C. Evaluation of open surgery for staghorn calculiin children. Child Nephrol Urol 1990;10:139-42.

4. * Aso Y, Ohta N, Nakano M, Ohtawara Y, Tajima A, Kawabe K.Treatment of staghorn calculi by fiberoptic transurethralnephrolithotripsy. J Urol 1990;144:17-19.

5. * Assimos DG, Wrenn JJ, Harrison LH, McCullough DL, BoyceWH, Taylor CL, Zagoria RJ, Dyer RB. A comparison of anat-rophic nephrolithotomy and percutaneous nephrolithotomy withand without extracorporeal shock wave lithotripsy for manage-ment of patients with staghorn calculi. J Urol 1991;145:710-14.

6. Assimos DG, Boyce WH, Harrison LH, McCullough DL,Kroovand RL, Sweat KR. The role of open stone surgery sinceextracorporeal shock wave lithotripsy. J Urol 1989;142:263-7.

7. * Beck EM, Riehle RA Jr. The fate of residual fragments afterextracorporeal shock wave lithotripsy monotherapy of infectionstones. J Urol 1991;145:6-10.

8. Beck EM, Vaughan ED Jr, Sosa RE. The pulsed dye laser in thetreatment of ureteral calculi [Review]. Semin Urol 1989;7:25-9.

9. * Begun FP, Jacobs SC, Lawson RK. Small-bowel perforationduring percutaneous nephrolithotomy. J Endourol 1989;3:81-4.

10. Begun FP, Jacobs SC, Lawson RK. Use of a prototype 3F elec-trohydraulic electrode with ureteroscopy for treatment of ureteralcalculous disease. J Urol 1988;139:1188- 91.

11. * Belis JA, Morabito RA, Kandzari SJ, Lai JCW, Gabriele OF.Anatrophic nephrolithotomy: preservation of renal functiondemonstrated by differential quantitative radionuclide renal scans.J Urol 1981;125:761-4.

12. * Blandy JP, Singh M. The case for a more aggressive approachto staghorn stones. J Urol 1976;115:505-6.

13. * Blandy JP, Tresidder GC. Extended pyelolithotomy for renalcalculi. Br J Urol 1967;39:121-30.

14. * Bloom LS, Nieh PT. Retrograde nephrostolithotomy in man-agement of complex renal calculi. J Urol 1991;145:706-9.

15. * Bhle A, Knipper A, Thomas S. Extracorporeal shock wavelithotripsy in paediatric patients. Scand J Urol Nephrol1989;23:137-40.

16. * Boyce WH. Surgery of urinary calculi in perspective. UrolClin North Am 1983;10:585-94.

17. * Boyce WH, Elkins IB. Reconstructive renal surgery followinganatrophic nephrolithotomy: followup of 100 consecutive cases.J Urol 1974;111:307-12.

18. Brown RD, Preminger, GM. Changing surgical aspects of uri-nary stone disease [Review]. Surg Clin North Am 1988;68:1085-1104.

19. Bruce RR, Griffith DP. Retrospective follow-up of patients withstruvite calculi. In: Smith LH, Robertson WGL, Finlayson, B,editors. Urolithiasis Clinical and Basic Research. New Yo

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