Oxalate Nephropathy Complicating Roux-en-Y Gastric Bypass

Abstract

Background and objectives: The most common bariatric surgery is Roux-en-Y gastric bypass (RYGB), which has been associated with hyperoxaluria and nephrolithiasis. We report a novel association of RYGB with renal insufficiency as a result of oxalate nephropathy.Design, setting, participants, & measurements: Eleven cases of oxalate nephropathy after RYGB were identified from the Renal Pathology Laboratory of Columbia University. The clinical features, pathologic findings, and outcomes are described.Results: Patients were predominantly white (72.7%) with a mean age of 61.3 yr. Indications for RYGB included morbid obesity (eight patients) and reconstruction after total gastrectomy for gastric cancer (three patients). All 11 patients had a history of hypertension, and 9 were diabetic. Patients presented with acute renal failure, often superimposed on mild chronic renal insufficiency (n ‫؍‬ 7), at a median of 12 mo after RYGB. The mean creatinine at baseline, at discovery of acute renal failure, and at biopsy was 1.5, 5.0, and 6.5 mg/dl, respectively. Renal biopsies revealed diffuse tubular degenerative changes, abundant tubular calcium oxalate deposits, and varying degrees of tubulointerstitial scarring. In addition, seven biopsies had underlying diabetic glomerulosclerosis and two had glomerulosclerosis attributable to obesity and hypertension. Eight of 11 patients rapidly progressed to ESRD and required hemodialysis at a mean of 3.2 wk after renal biopsy. The remaining three patients were left with significant chronic kidney disease.Conclusions: Oxalate nephropathy is an underrecognized complication of RYGB and typically results in rapid progression to ESRD. Patients with pre-existing renal disease may be at higher risk for this complication.

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

“…Oxalate nephropathy is a rare cause of acute and chronic renal failure (1)(2)(3)(4). Oxalate accumulation in renal allografts may arise de novo, or as "recurrence" of native kidney disease if underlying hyperoxalosis remains uncorrected.…”

“…Secondary hyperoxaluria can arise from a variety of different processes (Table 1), including iatrogenic causes. Gastrointestinal surgery is a known cause of hyperoxaluria, most notably in situations of fat malabsorption and diarrhea (1)(2)(3)(4).…”

“…However, recent data suggest that modern bariatric procedures, such as Roux-en-Y bypass, may also impart a twofold increased risk of nephrolithiasis, while 20-75% may have hyperoxaluria, including 20% with very high urine oxalate levels, also putting them at considerable risk of oxalate nephropathy (Table 2) (2,(5)(6)(7)(8)(9)(10)(11)(12). Purely restrictive bariatric procedures, such as gastric banding, may not increase oxalate excretion, yet more data are needed (Table 2) (13)(14)(15)(16).…”

“…We present two cases of renal allograft oxalate nephropathy, one that improved with conservative management, and one that was initially unrecognized on biopsy. 2 With fat malabsorption, hyperoxaluria is thought to result when excess free fatty acids complex with calcium in the gut, making calcium unavailable to bind oxalate, such that free oxalate is absorbed. The presence of high levels of free fatty acids and bile are also said to increase colonic mucosal permeability to oxalate.…”

Primary Hyperoxaluria: A Case Report and Review of the Literature

“…By light microscopy, calcium oxalate crystals are graywhite, speculated and are birefringent under polarized light, whereas calcium phosphate crystals do not polarize (5,7). Few or isolated tubular oxalate crystals are not rare in normal or failing kidneys, and in transplanted kidneys; their presence does not imply renal damage.…”