Bariatric Surgery increases risk of acute Kidney injury: Study

Researchers in Denmark analyzed outcomes for nearly 19,000 adults who underwent Roux-en-Y gastric bypass or sleeve gastrectomy between 2006 and 2018, comparing them to over 94,000 matched individuals with overweight or obesity who did not undergo surgery. Median follow-up was just over eight years.

Within one year of surgery, 2.7% of bariatric patients experienced AKI—significantly higher than matched controls. Over ten years, 3.5% developed nephrolithiasis compared to lower rates in non-surgical peers BioMed CentralPubMed. Adjusted hazard ratios confirmed elevated risk: AKI (aHR ≈ 1.63) and kidney stones (aHR ≈ 1.73) BioMed CentralPubMed.

The encouraging flip side: ten-year risks of CKD (stage G3–G5) and KFRT were significantly lower in the surgery group. CKD risk dropped to aHR ≈ 0.41, and KFRT to aHR ≈ 0.63, compared to non-surgery controls BioMed CentralPubMed.

The findings suggest bariatric surgery offers kidney protection in the long run—most likely driven by improved management of obesity-related comorbidities like hypertension, diabetes, and hyperlipidemia. However, the early risks of AKI and kidney stones—possibly due to volume shifts or oxalate handling—are real and warrant careful perioperative attention.

For clinicians, these results underscore the importance of closely monitoring renal function after bariatric procedures and implementing preventive strategies—hydration, renal monitoring, possibly dietary oxalate restriction—to mitigate early risks while aiming for those long-term gains.