Peritransplant Orlistat Use and Post-Transplant Oxalate Nephropathy: A Cautionary Tale

Introduction: Obesity poses important challenges to ESKD patients awaiting kidney transplantation. Weight loss prior to transplantation is often recommended for successful post transplant outcomes. There are no set guidelines on monitoring patients on prescribed weight loss medications in the peri-transplant period. Here, we report a rare case of oxalate nephropathy leading to primary allograft failure from peri-transplant use of Orlistat. Case Description: A 71-yr old male ESKD patient with biopsy proven hypertensive nephrosclerosis on peritoneal dialysis for approximately 51 months received a deceased donor renal transplant (2 Antigen match kidney with KDPI score of 71%). Clinical course was complicated by delayed graft function (DGF) requiring dialysis on day 1 of post transplant and he continued to be oligo-anuric. A kidney biopsy done 3 weeks post-transplant revealed acute tubular injury with marked oxalate nephropathy (Image 1). His serum oxalate level 4 weeks post-transplant was 78 micromol/L (refernce range 2.0 micromol/L). Patient was meticulous with following recommendations and denied incorporating any high oxalate diet. On furthe review of his peri-transplant course, he was started on Orlistat 120 mg three times daily 6 months prior to transplantation for weight loss to qualify for transplant listing at a BMI of 35-36. He continued to take Orlistat till it was discontinued on the day of transplant. Discussion: We report the first case of oxalate nephropathy in a newly transplanted kidney from peri-transplant use of Orlistat. Our case high lights the perils and the many unknowns of monitoring and management of patients on weight loss medications like Orlistat in the peri-transplant period. Our experience has led to discontinuing Orlistat on all wait listed kidney transplant patients at our center.Oxalate deposition on H&E staining on kidney biopsy