Enteric Oxalate Nephropathy in the Renal Allograft: An Underrecognized Complication of Bariatric Surgery

Abstract

Enteric hyperoxalosis is a recognized complication of bariatric surgery, with consequent oxalate nephropathy leading to chronic kidney disease and occasionally end-stage renal failure. In patients with prior gastrointestinal bypass surgery, renal allografts are also at risk of oxalate nephropathy. Further, transplant recipients may be exposed to additional causes of hyperoxalosis. We report two cases of renal allograft oxalate nephropathy in patients with remote histories of bariatric surgery. Conservative management led to improvement of graft function in one patient, while the other patient returned to dialysis. Interpretation of serologic, urine and biopsy studies is complicated by oxalate accumulation in chronic renal failure, and heightened excretion in the early posttransplant period. A high index of suspicion and careful clinicopathologic correlation on the part of transplant nephrologists and renal pathologists are required to recognize and treat allograft oxalate nephropathy. As the incidence of obesity and pretransplant bariatric surgery increases in the transplant population, allograft oxalate nephropathy is likely to be an increasing cause of allograft dysfunction.

Intensive weight loss combining flexible dialysis with a personalized, ad libitum, coach‐assisted diet program. A “pilot” case series

“…The data compare favorably with the results of bariatric surgery, highly effective in dialysis patients, but not devoid of severe side effects …”

“…The data compare favorably with the results of bariatric surgery, highly effective in dialysis patients, but not devoid of severe side effects. 19,20 Patients' opinions were favorable, underlining the advantage of rapid weight loss, allowing wait-listing for kidney transplantation. Patients' motivation in this "pilot adventure" has probably been a key point together with the strong bonds with the caregivers; nonetheless, this is shared by most of successful weight loss-educational approaches.…”

Gastric bypass oxalosis in renal transplant: clinicopathologic correlates

“…Increasing reports of oxalate nephropathy and renal transplant graft loss likely due to enteric hyperoxaluria from gastric bypass are emerging. [15] This study shows that oxalate nephropathy and graft loss do not uniformly occur in renal transplant recipients who have had malabsorptive forms of bariatric surgery such as Roux en Y and jejunoileal bypass surgery for obesity. The development of oxalate nephropathy in three of our patients is multifactorial and likely precipitated by AKI from volume depletion, sepsis or rejection.…”

Lost in Transportation: Calcium Oxalate Crystals in Kidney Biopsy Specimens Fixed in Michel Medium May Disappear

“…5,6 Additionally, if the diagnosis is missed and the underlying cause of hyperoxalosis is not corrected, the disease may also recur in the renal allograft following transplant as previously reported. 2,3 Our study is based on biopsies in which MTM was used to preserve kidney tissue for IF. We do not know whether other tissue preservation media have similar issues regarding the preservation of CaOx.…”

“…They have been reported in up to 1% of native kidneys and up to 4% of renal allograft biopsies, 1 where they can be seen in association with acute tubular injury or chronic renal failure, as well as recurrent or de novo oxalate nephropathy. 2,3 Although there is no specific cutoff number of CaOx casts, when the number of CaOx deposits in the kidney biopsy specimen appears excessive, a diagnosis of oxalate nephropathy can be made in the appropriate clinical scenario. The amount of CaOx deposits detected by the renal pathologist has significant implications because it impacts the differential diagnosis of incidental CaOx deposits (as seen in severe acute tubular necrosis or true oxalate nephropathy).…”