Kidney International, Vol. 42 (1992), pp. 1408—1411

Success of kidney transplantation in oxalosis is unrelated toresidual hepatic enzyme activity

Avi KATZ, DEBORAH FREESE, CHRISTOPHER J. DANPURE, JONATHAN I. SCHEINMAN,and S. MICHAEL MAUER

Department of Pediatrics, Shaare Zedek Medical Center, Jerusalem, Israel; The Department of Pediatrics, University of Minnesota MedicalSchool, Minneapolis, Minnesota, USA; The Clinical Research Center, Middlesex, England, United Kingdom; and Department of Pediatrics,

Duke University Medical Center, Durham, North Carolina, USA

Success of kidney transplantation in oxalosis is unrelated to residualhepatic enzyme activity. We evaluated hepatic alanine glyoxylate ami-notransferase (AGT) activity in percutaneous hepatic biopsy materialobtained from four children with long-term renal allograft functionfollowing transplantation for primary hyperoxaluria type 1 (PH 1). Thestudy was performed to determine whether these successes had oc-curred because relatively high residual levels of AGT activity hadintroduced a selection bias. The children ranged from seven months toeight years at transplant and are currently well 7 to 11 years later, withno oxalate deposition on repeated allograft biopsies and creatinineclearances of 80 to 128 mI/min/! .73 m2. AGT activity ranged from 0 to13.8%, and in two of three patients with detectable levels the AGT wasin mitochondrja rather than peroxisomes. These results indicate thatlong-term renal allograft success can occur in spite of severe AGTdeficiency. Thus, the therapeutic choice of kidney alone versus com-bined kidney-liver transplant cannot currently be made by measuringresidual hepatic AGT in PH 1. Kidney transplant alone remains areasonable initial therapeutic alternative for patients with recent onsetof renal insufficiency due to PH 1.

Primary hyperoxaluria type 1 (PH 1) is an autosomal reces-sive disorder caused by a deficiency of the hepatic peroxisomalenzyme alanine:glyoxylate aminotransferase (AGT) [1]. Pa-tients with PH 1 manifest increased synthesis and urinaryexcretion of oxalate, urolithiasis, and a high risk of a gradualreduction in renal function leading to end-stage renal disease(ESRD) in late childhood and early adulthood [2]. A moresevere, albeit rare, form of the disease is encountered in infantspresenting in ESRD due to nephrocalcinosis with no antecedentstone disease [2—7]. Since the oxalate removal rate by dialysis isless than its endogenous production rate, calcium oxalatecontinues to accumulate in the body of PH 1 patients withESRD, eventually leading to systemic oxalosis and the patient'sdemise [8—10].

Although renal transplantation was introduced in the 1970'sas a treatment for ESRD in PH 1 patients, a high failure ratewith this procedure has been reported by most transplantationcenters [11]. Recent data from the European Dialysis and

Received for publication February 6, 1992and in revised form July 13, 1992Accepted for publication July 13, 1992

C 1992 by the International Society of Nephrology

Transplantation Association (EDTA) registry summarizing 20years experience with kidney transplantation for PH 1, cites athree-year graft survival of 23% for patients receiving a livingrelated donor and 18% cadaveric donors. The more recentresults in the EDTA series are only slightly better [12].

Due to the high failure rate of kidney transplantation, andbecause the basic biochemical defect (AGT deficiency) is in theliver, some centers now advocate liver transplantation (mostoften combined with kidney transplantation) as the procedureof choice for PH 1 patients with ESRD [13—19].

Some of us have previously reported long-term patient sur-vival with excellent graft function in patients who receivedkidney transplants for ESRD secondary to presumed PH 1 [20].All the patients had presented with ESRD and therefore defin-itive diagnosis by urine/plasma oxalate measurement had notbeen possible. The relatively high success rate in these patientshas been attributed to early transplantation, aggressive pre-transplantation dialysis and the use of a medical protocolpreviously outlined in detail [20]. More recently we havereported our long-term follow-up of eight PH 1 children treatedwith renal transplantation. Four of these eight patients havenow survived 6.5 to 10.5 years after renal transplantation andstill maintain good renal function with no evidence of renaloxalate deposition on renal allograft biopsies [21]. In an attemptto determine whether the successful long-term outcome of renaltransplantation was the result of clinical management or someintrinsic (genetic) characteristic of their disease, we have deter-mined the degree of hepatic AGT deficiency in these patients.

Methods

PatientsThe four patients included in this study were selected from

eight previously reported patients because of their long-termsuccess following kidney transplantation for PH 1. The otherfour patients are dead [21].

All presented with ESRD secondary to nephrocalcinosiswithout antecedent urolithiasis (Table 1). All had extrarenaloxalate deposits. The four were treated according to a previ-ously described protocol: early transplantation and aggressivepre-transplantation dialysis. Following transplantation the pa-tients were maintained on high fluid intake, vitamin B6, mag-nesium, orthophosphate supplementation and thiazide diuretics

1408

Katz et a!: Kidney transplant in PH 1 children 1409

Table 1. Patient characteristics

Patient

Age

ESRDb

in months

TX-i TX-2Reason for 1stallograft failure

Current status Hepatic AGT

Follow upsince last TX

monthsGFR

mI/mm/I .73 m2Allograftoxalosis

Age atliver biopsy

monthsEnzymeactivity CRM

Subcellularlocalization

i234

783.52.03.0

9677

16

—30—24

—Pneumoccocal sepsis

—Sepsis, dehydration

120849672

9710180

128

nonenonenonenone

2041089684

05.69.1

13.8

—

++

+++

—P + M

—M

AGT was corrected for crossover from glutamate glyoxylate aminotransferase for patient #1. For patients #2, 3 and 4, the crossover could onlybe estimated. AGT activity is expressed as % of the mean of the control value (Danpure and Jennings 1988). Abbreviations are: CRM, presenceof immunologically cross reactive material (+ + + + normal; — undetectable); P, peroxisomal; M, mitochondrial; TX, transplantation; GFR,glomerular filtration rate determined by creatinine clearance.

a In a graft biopsy 60 months following transplantationb All patients anuric or severely oliguric at presentation

[20]. All had bilateral nephrectomy and splenectomy at orbefore transplantation. All grafts were from living relateddonors. Cyclosporine was not available for use at the time thesetransplants were performed and immunosuppression includedazathioprine (Imuran), prednisone, and, for induction, 14 daysof antilymphoblast globulin.

Patients #2 and #4 required retranspiantation (Table 1). Thefirst allograft in patient #2 failed 20 months post-transplantationfollowing an episode of overwhelming pneumococcal sepsiswith shock and cerebral vascular thrombosis and infarction.Failure of the primary graft in patient #4 occurred three monthspost-transplantation and was associated with small bowel ob-struction and dehydration, E. coli sepsis, and urinary tractinfection, and cytomegalovirus infection.

All four patients are currently well 7 to 11 years followingtransplantation with creatinine clearance of 80 to 128 mi/minI1.73 m2 (Table 1). There was no evidence of calcium oxalate orcalcium phosphate deposition in the kidney.

Study protocolFor the purpose of this study all four patients were admitted

to the Clinical Research Center at the University of Minnesota(U of M) to participate in a protocol approved by the Committeefor the use of Human Subjects in Research at the U of M. Allfour patients underwent percutaneous kidney and liver biop-sies. All but one patient had adequate kidney and liver tissue foranalysis. In patient #3 the liver specimen was inadequate forimmunoelectron microscopy.

Laboratory methodsGlomerular filtration rate (GFR) was assessed using creati-

nine clearance. Serum and urinary creatinine were measuredusing the Jaffè method [221.

To make a definitive enzymological diagnosis in the patientsunder this study, percutaneous needle liver biopsies wereperformed. Portions of each biopsy were fixed in 1% glutaral-dehyde and used for the determination of the intracellularlocalization of AGT by post-embedding protein-A gold immu-noelectron microscopy [23]. The remainder of each biopsy wasfrozen until required for the determination of AGT enzymeassay using the macro-spectrophotometric method in patient #1[24] and the micro-radioactive electrophoretic method [25] for

patients #2 through 4. The presence of immunoreactive AGTwas established by SDS-PAGE/Western blotting [251.

Results

All four patients in the present study had marked deficienciesin hepatic AGT activity (0 to 13.8%) and immunoreactiveprotein (Table 1). These data confirm the diagnosis of PH 1. Inaddition, in two of the three patients with detectable levels ofAGT, the enzyme was found localized within the mitochondriarather than in the peroxisomes, but it could not be studied inone. In patient #4 the AGT was >90% within the mitochondria,while in patient #2 —50% of the gold particles were in mito-chondria and the remaining particles in peroxisomes. In thesingle patient with 0% hepatic AGT activity no immune reactiveAGT was detected.

Confirming earlier studies on these patients, and as statedabove, all patients have excellent graft function as evidenced bynormal GFR's and no evidence of calcium oxalate or calciumphosphate deposition in the allograft (Table 1).

Discussion

Four of eight of the children with PH 1 transplanted at ourcenter have achieved long-term renal graft function. One mightspeculate that these successes could have represented a selec-tion bias because these patients happened to have a higher levelof hepatic AGT than most PH 1 patients with renal failure.However, the current study clearly shows that our four long-term survivors all had severe enzyme defects associated inthree with aberrant localization of the enzyme, thus establishingthe diagnosis of PH 1 and ruling out secondary causes ofhyperoxaluria, and primary hyperoxaluria type 2 [26—28]. Thesmall number of patients does not permit us to determinewhether the long term success of kidney transplantation may berelated to a higher percent of patients with residual AGTactivity than has been previously reported elsewhere (24/59 vs.3/4 in our series) [27]. However, it is reasonable to concludefrom our results that neither severe clinical presentation withrenal failure in infancy or early childhood nor complete absenceof hepatic AGT enzyme activity precludes successful kidneytransplantation.

The recent association of PH 1 with defects, both genotypic[29, 30] and phenotypic [1], in AGT coupled with the immediate

1410 Katz et a!: Kidney transplant in PH 1 children

correction of urinary oxalate overexcretion following livertransplantation [15] suggest that hepatic AGT is an importantdeterminant of the level of endogenous oxalate production.However, in patients with PH 1, the relationship betweenhepatic enzyme level and location with the renal filtered load ofoxalate or with the rate of development of renal injury iscomplex and poorly understood [28, 31, 32]. In accord with thisis our experience that the only patient in our series with totalabsence of AGT (patient #1), had the mildest clinical coursewith ESRD, presenting at six years of age, and did not requireretranspiantation. Further, variability in the clinical course ofpatients with similar AGT levels suggests that residual AGTactivity may be only one of several genetic and environmentalfactors dictating the natural history of PH 1. Such factors mayinclude: the activity of other enzymes capable of affectingoxalate synthesis, variation in urinary solubility of oxalate,nutrition, and climate [28]. These unknown factors, as well asvariables such as total body oxalate load and clinical manage-ment, may influence renal allograft outcome.

It is therefore not surprising that the current study does notsupport the concept that hepatic AGT activity can be used asthe sole means for selecting the transplant procedure of choicein the individual PH 1 patient. Thus, there is currently no singlefactor capable of determining this decision. It is possible thatcareful study of a larger number of patients could elucidate aclearer decision making paradigm. However, this will be a slowtask considering the rarity of the disease, the high mortality ratewith all current treatment modalities, and variations in manage-ment approaches between centers.

The present study confirms the value of kidney transplanta-tion for some patients with ESRD due to PH 1. Recentlyreported short term results of combined liver-kidney transplan-tation in adults are similar to ours with kidney transplantationalone [18]. Our experience with kidney transplantation both inadults [20] and children [21] indicates that the loss of renalallograft in PH 1 patients is a two stage process requiring first areduction in graft function (rejection, obstruction, dehydration,etc). followed later by diffuse oxalate deposition in the kidney.The majority of such events occur during the first post-trans-plant year when the oxalate burden (consisting of endogenousproduction and mobilization of tissue stores) is at its peak. Latecomplications are rare as evidenced by the stable late post-transplant course of our patients. Thus, the major advantage ofliver transplantation is in reducing the oxalate load during thiscritical period rather than in the ultimate cure of a disease thatmay take two to three decades prior to reaching renal failure(probably longer if adequately treated). We would thereforereserve liver transplantation for patients with clinical evidenceof markedly increased oxalate tissue stores, and/or patientsmanaged by regular dialysis for more than one year. A loss of arenal allograft would serve as an indication for liver transplan-tation only if it occurred in spite of optimal management. Otherfactors which may favor liver transplantation would be highoxalate production rate (evidenced by high oxlate excretion rateand/or tissue oxalate accretion [33]) and a rapid course frompresentation to ESRD. Kidney transplantation should be per-formed prior to renal failure [34]. These recommendations willneed to be reviewed when long-term follow-up of liver trans-plantation results in PH 1 become available and more experi-ence with early kidney transplantation is obtained.

Acknowledgments

The technical assistance of P.R. Jennings and K.M. Guttridge isgratefully acknowledged. These studies were supported by NIH grants#M0l-RROO400 and #DK08232-02.

Reprint requests to S. Michael Mauer, M.D., Department of Pedi-atrics, University of Minnesota Medical School, Box 491 UMHC, 515Delaware Street S.E., Minneapolis, Minnesota 55455, USA.

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