Acute oxalate nephropathy following kidney transplantation: Report of three cases

Primary hyperoxaluria diagnosed after kidney transplant: A review of the literature and case report of aggressive renal replacement therapy and lumasiran to prevent allograft loss

Primary hyperoxaluria type 1 is a rare inherited disorder caused by abnormal liver glyoxalate metabolism leading to overproduction of oxalate, progressive kidney disease, and systemic oxalosis. While the disorder typically presents with nephrocalcinosis, recurrent nephrolithiasis, and/or early chronic kidney disease, the diagnosis is occasionally missed until it recurs after kidney transplant. Allograft outcomes in these cases are typically very poor, often with early graft loss. Here we present the case of a child diagnosed with primary hyperoxaluria type 1 after kidney transplant who was able to maintain kidney function, thanks to aggressive renal replacement therapy as well as initiation of a new targeted therapy for this disease. This case highlights the importance of having a high index of suspicion for primary hyperoxaluria in patients with chronic kidney disease and nephrocalcinosis/nephrolithiasis or with end stage kidney disease of uncertain etiology, as initiating therapies early on may prevent poor outcomes.

Dietary Oxalate Intake and Kidney Outcomes

Oxalate is both a plant-derived molecule and a terminal toxic metabolite with no known physiological function in humans. It is predominantly eliminated by the kidneys through glomerular filtration and tubular secretion. Regardless of the cause, the increased load of dietary oxalate presented to the kidneys has been linked to different kidney-related conditions and injuries, including calcium oxalate nephrolithiasis, acute and chronic kidney disease. In this paper, we review the current literature on the association between dietary oxalate intake and kidney outcomes.

The association of calcium oxalate deposition in kidney allografts with graft and patient survival

BACKGROUND

Whether calcium oxalate (CaOx) deposition in kidney allografts following transplantation (Tx) adversely affects patient outcomes is uncertain, as are its associated risk factors.

METHODS

We performed a retrospective cohort study of patients who had kidney allograft biopsies performed within 3 months of Tx at Brigham and Women's Hospital and examined the association of CaOx deposition with the composite outcome of death or graft failure within 5 years.

RESULTS

Biopsies from 67 of 346 patients (19.4%) had CaOx deposition. In a multivariable logistic regression model, higher serum creatinine [odds ratio (OR) = 1.28 per mg/dL, 95% confidence interval (CI) 1.15-1.43], longer time on dialysis (OR = 1.11 per additional year, 95% CI 1.01-1.23) and diabetes (OR = 2.26, 95% CI 1.09-4.66) were found to be independently associated with CaOx deposition. CaOx deposition was strongly associated with delayed graft function (DGF; OR = 11.31, 95% CI 5.97-21.40), and with increased hazard of the composite outcome after adjusting for black recipient race, donor type, time on dialysis before Tx, diabetes and borderline or acute rejection (hazard ratio 1.90, 95% CI 1.13-3.20).

CONCLUSIONS

CaOx deposition is common in allografts with poor function and portends worse outcomes up to 5 years after Tx. The extent to which CaOx deposition may contribute to versus result from DGF, however, cannot be determined based on our retrospective and observational data. Future studies should examine whether reducing plasma and urine oxalate prevents CaOx deposition in the newly transplanted kidney and whether this has an effect on clinical outcomes.

Impact of Regular or Extended Hemodialysis and Hemodialfiltration on Plasma Oxalate Concentrations in Patients With End-Stage Renal Disease

Introduction

Calcium oxalate supersaturation is regularly exceeded in the plasma of patients with end-stage renal disease (ESRD). Previous reports have indicated that hemodialfiltration (HDF) lowers elevated plasma oxalate (P_Ox) concentrations more effectively compared with hemodialysis (HD). We reevaluate the therapeutic strategy for optimized P_Ox reduction with advanced dialysis equipment and provide data on the effect of extended treatment time on dialytic oxalate kinetics.

Methods

Fourteen patients with ESRD who underwent HDF 3 times a week for 4 to 4.5 hours (regular HDF; n = 8) or 7 to 7.5 hours (extended HDF; n = 6) were changed to HD for 2 weeks and then back to HDF for another 2 weeks. P_Ox was measured at baseline, pre-, mid-, and postdialysis, and 2 hours after completion of the treatment session.

Results

Baseline P_Ox for all patients averaged 28.0 ± 7.0 μmol/l. Intradialytic P_Ox reduction was approximately 90% and was not significantly different between groups or treatment modes [F(1) = 0.63; P = 0.44]. Mean postdialysis P_Ox concentrations were 3.3 ± 1.8 μmol/l. A rebound of 2.1 ± 1.9 μmol/l was observed within 2 hours after dialysis. After receiving 2 weeks of the respective treatment, predialysis P_Ox concentrations on HD did not differ significantly from those on HDF [F(1) = 0.21; P = 0.66]. Extended treatment time did not provide any added benefit [F(1) = 0.76; P = 0.40].

Discussion

In contrast to earlier observations, our data did not support a benefit of HDF over HD for P_Ox reduction. With new technologies evolving, our results emphasized the need to carefully reevaluate and update traditional therapeutic regimens for optimized uremic toxin removal, including those used for oxalate.

Late diagnosis of primary hyperoxaluria type III

We report the case of a 78-year-old patient with late diagnosis of hyperoxaluria type III (PH3). He developed renal failure after nephrectomy for clear cell papillary renal carcinoma and complained of recurrent urolithiasis for some 30 years, whose aetiology was never identified. Biochemical laboratory investigations of urine and urolithiasis composition revealed marked hyperoxaluria but normal concentrations of urinary glyceric and glycolic acid as well as stones of idiopathic calcium-oxalate appearance. Furthermore, the dietary survey showed excessive consumption of food supplements containing massive amounts of oxalate precursors. However, the persistence of excessive hyperoxaluria after his eating habits was changed leading us to perform molecular genetic testing. We found heterozygous mutations of the recently PH3-associated HOGA1 gene when sequencing PH genes. This is the first description of late diagnosis primary PH3 in a patient with several additional pro-lithogenic factors. This case illustrates the importance of undertaking a complete biological work-up to determine the aetiology of hyperoxaluria. This may reveal underdiagnosed primary hyperoxaluria, even in older patients.

Identification of a novel AGXT gene mutation in primary hyperoxaluria after kidney transplantation failure

Primary hyperoxaluria is a genetic disorder in glyoxylate metabolism that leads to systemic overproduction of oxalate. Functional deficiency of alanine-glyoxylate aminotransferase in this disease leads to recurrent nephrolithiasis, nephrocalcinosis, systemic oxalosis, and kidney failure. The aim of this study was to determine the molecular etiology of kidney transplant loss in a young Tunisian individual. We present a young man with end-stage renal disease who received a kidney allograft and experienced early graft failure. There were no improvement in kidney function; he required hemodialysis and graft biopsy revealed calcium oxalate crystals, which raised suspicion of primary hyperoxaluria. Genetic study in the AGXT gene by PCR direct sequencing identified three missense changes in heterozygote state: the p. Gly190Arg mutation next to two other novels not previously described. The classification of the deleterious effect of the missense changes was developed using the summered results of four different mutation assessment algorithms, SIFT, PolyPhen, Mutation Taster, and Align-GVGD. This system classified the changes as polymorphism in one and as mutation in other. The patient was compound heterozygous mutations. Structural analysis showed that the novel mutation, p.Pro28Ser mutation, affects near the dimerization interface of AGT and positioned on binding site instead of the inhibitor, amino-oxyacetic acid (AOA). With the novel AGXT mutation, the mutational spectrum of this gene continues to broaden in our population. The diagnosis of PH1 was not recognized until after renal transplant with fatal consequences, which led us to confirm the importance of screening before planning for kidney transplantation in population with a relatively high frequency of AGXT mutation carriers.