Acute oxalate nephropathy seven years post Roux-en-Y gastric bypass surgery without excessive vitamin C intake: a case report.

[BACKGROUND] Acute oxalate nephropathy is a progressive kidney condition characterized by the accumulation of oxalate crystals, causing interstitial nephritis and tubular damage. Excessive intake of vitamin C, obesity, chronic inflammatory bowel disease, and gastric bypass surgery are risk factors that can cause oxalate nephropathy. However, the risks associated with this condition and its management deserve further investigation.

[CASE PRESENTATION] A 76-year-old woman had undergone Roux-en-Y gastric bypass surgery seven years prior following a diagnosis of gastric cancer. Four years previously, the patient was diagnosed with remitting seronegative symmetrical synovitis with pitting edema (RS3PE) syndrome and was prescribed 5 mg of prednisolone and an active vitamin D supplement. There was no incidence of vitamin C overdose, nor did she use ethylene glycol lotion. Her initial creatinine level was 0.72 mg/dL, which increased to 6.17 mg/dL six months later. Renal biopsy revealed deposits of oxalate crystals in the renal tubules. She was diagnosed with acute oxalate nephropathy and treated with prednisolone 35 mg/day. However, her renal function continued to deteriorate, and she had to undergo hemodialysis one month later. After two months, she developed thrombocytopenia and hemolytic anemia, and her blood pressure decreased during hemodialysis. She was diagnosed with thrombotic microangiopathy (TMA) and treated medically but unfortunately did not survive.

[CONCLUSIONS] Our findings indicate that oxalate nephropathy can occur even several years after Roux-en-Y gastric bypass. In addition, the use of prednisolone for treating oxalate nephropathy could also have contributed to the exacerbation of renal failure. Early detection and prevention of this condition is currently the best option.