Acute kindey failure leading to permanent hemodalysis due to hyperoxaluria following OAGB related rapid weight loss. Case report

The one-anastomosis laparoscopic gastric bypass (OAGB) has prooved to provide good weight loss, comorbidity improvement, and quality of life with follow-up longer than 5 years. Although capable of improving many obesity-related diseases OAGB is associated with post-operative medical complication mainly related to the induced malabsorption. A 52 years old man affected by nephrotic syndrome due to a focal and segmental glomerulosclerosis underwent OAGB uneventfully. At 3 months from surgery patient had lost 40 kg reaching a BMI of 32. Patient was admitted in Nephrology unit for acute kidney injury with only mild improvement in renal function (SCr 9 mg/dl); proteinuria was still elevated (4 g/24h), with microhematuria. Renal biopsy was performed: oxalate deposits were demonstrated inside tubules, associated with acute and chronic tubular and interstitial damage and glomerulosclerosis (21/33 glomeruli). Urinary oxalate level was than found elevated (72 mg/24h, range 13-40), providing the diagnosis of acute kindey injury due to hyperoxaluria potentially associated to OAGB. No recovery in renal function was observed and the patient remained dialysis-dependent. The early and rapid excessive weight loss in patients affected by chronic kindey insufficiency could be associated with the worsening of renal function. Calcium oxalate increased levels associated to to the OAGB related malabsorption could be a key factor in kidney injury