Oxalate nephropathy in a diabetic patient after gastric by-pass

We report a case of 48-year-old woman with history of diabetes and hypertension, who presented with acute to chronic kidney injury. Sixteen months before presentation, she had undergone Roux-en-Y gastric by-pass (RYGB) for morbid obesity. Kidney biopsy showed lesions consistent with oxalate nephropathy and deposition of calcium oxalate crystals. An extensive workshop excluded other causes of kidney injury. The patient subsequently required dialysis with no improvement of renal function on follow-up. The mechanism by which patients develop hyperoxaluria after RYGB remains obscure; it is suggested that RYGB provokes fat malabsorption, which results in increased load of free fatty acid in the intestine. Thus, calcium binds to free fatty acids provoking reduced synthesis of calcium oxalate. Consequently, increased quantity of oxalate remains free and is absorbed in the intestine causing hyperoxaluria. Similar to our case, oxalate nephropathy after RYGB is seen in patients with diabetes, hypertension and chronic kidney injury. Treatment includes low-fat, low-oxalate diet along with administration of calcium supplements. Unfortunately, prognosis is rather poor with the majority of patients eventually requiring permanent dialysis. Therefore, patients with history of chronic kidney disease undergoing RYGB should be closely monitored, particularly those with long standing history of diabetes and hypertension.