Staghorn Calculus – Etiology, Management & Prevention

BACKGROUND• infection stones, struvite, triple phosphate stones,

staghorn calculus.• Magnesium Ammonium Phosphate (MgNH4PO4·6H2O)

+ calcium carbonate apatite crystals (Ca10(PO4)6·CO3) Potential for morbidity and mortality:1. Untreated infection stones – progressive renal demise2. Inadequately treated struvite stone – niduses for

recurrent UTI and recurrent struvite stone formation.3. bacteria reside within these stones – life-threatening

sepsis

Pathogenesis

• Infection stone =

urine pH is > 7.2urease-producing

bacteria

• (NH2 )2CO + H2O → 2NH3 + CO2

• NH3 + H2O → NH4+ + OH− pK = 9.0

• presence of urease, ammonia continues to be produced despite alkaline urine, further increasing urinary pH.

• Promotes the hydration of carbon dioxide to carbonic acid

• CO2 +H2O→ H2CO3 pK = 4.5 • H2CO3 → H+ + HCO3

− pK = 6.3• HCO3- → H+ + CO3

2- pK= 10.2

• The dissociation of hydrogen phosphate under alkaline conditions provides phosphate

OTHER FACTORS:• The relative decrease in stone inhibitors(citrate) may also

play a role in struvite physicochemistry.• GAGs theory• Stasis

Bacteriology• family Enterobacteriaceae comprises the majority of

urease-producing pathogens• The most common urease-producing pathogens are

Proteus, Klebsiella, Pseudomonas, and Staphylococcus species

• Proteus mirabilis the most common organism associated with infection stones

• Bacterial urease can be detected by the Urea-Rapid Test• E. coli and Proteus, may alter the activity of urokinase• and sialidase,

Epidemiology• Infection stones comprise 5% to 15% of all stones• More often in women (ratio of 2 : 1)Increased risk for infection calculi:1. Elderly 2. premature infants3. diabetics4. urinary stasis as a result of urinary tract obstruction,

urinary diversion, or neurologic disorders. 5. Spinalcord–injured patients 6. use of indwelling catheters

CLINICAL FINDINGSA complete history• of chronic flank pain, malaise, fever, • dysuria, and intermittent hematuria• immunosuppressed state (diabetes mellitus,

steroid intake, etc.),• history of previous stone disease• past surgical history - for urological procedures• history of using multiple, alternating antibiotics

Physical Examination• a chronically ill-appearing patient• Body habitus,• presence of vertebral kyphoscoliosis• In acute pyelonephritis or pyonephrosis -

1. toxic appearance2. costovertebral angle tenderness

Laboratory studies• complete blood count• basic metabolic panel• Urinalysis• Urine culture

Imaging Modalities

• Renal sonography• X ray KUB• IVP• CT urography• Nuclear renography

NATURAL HISTORY OF INFECTION STAGHORN CALCULI

• Pyonephrosis• xanthogranulomatous pyelonephritis• end stage hydronephrotic kidney• severe pyelonephritic changes• Perinephric abscess• Carcinoma• the overall rate of renal deterioration was 28%– Solitary, previous, recurrent, hypertension, complete,

diversion, neurogenic bladder, refused treatment• asymptomatic

TREATMENT• The primary goal of staghorn stone management is complete stone

eradication.• Various modalities of treatments are:

– Surgical• PCNL• ESWL• OPEN• SANDWICH THERAPY

– Non surgical• Dissolution therapy• Antibiotics• urease inhibitors,• urinary acidification, • dietary modification.

Percutaneous Nephrostolithotomy (PCNL)the treatment of choice• superior stone-free outcomes• acceptably low morbidity.• Stone free rate of ~80%• overall risk of transfusion was 18%• serious complications was 15%. i.e.

– injury to adjacent organs (colon, spleen, liver), – hydropneumothorax, – collecting system perforations,– sepsis, – vascular injury, – renal loss.

Technical advances in PCNL1. flexible nephroscopy is mandatory after

debulking the dominant stone2. to establish multiple percutaneous tracts3. second look nephroscopy.

Extracorporeal Shockwave Lithotripsy (Monotherapy)

• SWL is the least invasive of the operative approaches• SWL monotherapy had the lowest success rate.• Risks included – colic requiring admission, – significant perirenal hematoma, – obstruction including steinstrasse,– pyelonephritis,– renal loss.

• “sandwich therapy”- pcnl -> eswl -> pcnl

Ureteroscopy

• flexible ureteroscopy has been used in combination with PCNL – to avoid multiple access tracts– to access calyces that would be difficult to access

in an antegrade manner

Open & Laparoscopic Surgery• Anatrophic nephrolithotomy and pyelolithotomy

operations• alternative in patients who require concomitant

heminephrectomy, pyeloplasty • in those with ectopic kidneys that cannot be safely

accessed percutaneously• Other indications:– morbid obesity, – large symptomatic anterior caliceal diverticular stones, – large stone volume with infundibular stenosis – massive collecting system dilation

Dissolution therapy• Boric acid and permanganate• Suby’s solution G• Hemiacidrin or Renacidin® adding D-gluconic acid.• following precautions must be exercised during intrarenal chemolysis:

– Low intrarenal pressures must be maintained (<30 cm water),– Serum magnesium and phosphate must be monitored closely,– The urine must be sterile. Broad-spectrum antibiotics are given for 14 days in

the perioperative period,– The collecting system must be unobstructed and there must be no

extravasation.• Indication: in high-risk patients, with residual calculi after percutaneous

renal surgery.• Demerits : prolonged hospital stay, cost and risk of complications.

Antibiotics

• Culture-specific preoperative and perioperative antibiotics are critical to prevent sepsis

• Long-term, low-dose, culture specific antimicrobials are important to prevent new stone growth and progression after surgery.

• AUA Guidelines Panel stated emphatically that treatment with antibiotics alone is not standard of care.

Urease Inhibitors• Acetohydroxamic acid (AHA) is the only FDA-approved

urease inhibitor.• Irreversibly inhibits bacterial urease• High renal clearance, • Penetrate the bacterial cell wall,• Acts synergistically with several antibiotics• Adverse effects- tremulousness, thrombophlebitis,

neurologic, hematologic, and dermatologic.• Contraindicated in patients with serum creatinine

greater than 2.5 mg/dL

Urinary acidification

• L-methionine to acidify urine• oral intake of 1,500–3,000 mg daily of L-

methionine• gastric patch pyeloplasty (animal model)

Dietary modification

Aim :To deplete the substrates of struvite calculi, including

urinary phosphate, magnesium, and ammonia.• (Shorr regimen) a regimen of a low-phosphorous,

low-calcium diet with oral estrogens and aluminum hydroxide gel

• Adverse effects: constipation, anorexia, lethargy, bone pain, and hypercalciuria, increased risk of breast and uterine cancers.

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