Acute kidney injury after gastric bypass surgery.

Gastric bypass surgery is a common treatment for morbid obesity. The presence of comorbid conditions and drugs that are used to treat them can adversely influence kidney function. Risk factors and outcomes of acute kidney injury (AKI) after gastric bypass surgery are not well understood, however. A total of 504 patients underwent gastric bypass between January 2003 and 2005. Primary outcome was AKI, defined as a > or =50% increase in serum creatinine relative to baseline or requirement of dialysis. Secondary outcomes were duration of hospitalization, all-cause hospital mortality, and readmissions within 30 d after surgery. Demographic, comorbid, and laboratory variables and preoperative medication use were examined as potential risk factors for AKI. A total of 42 (8.5%) patients developed postoperative AKI. Hyperlipidemia, preoperative use of angiotensin-converting enzyme inhibitors (ACE-I) or angiotensin receptor blockers (ARB), intraoperative hypotension, and higher body mass index were associated with increased frequency of AKI. By multivariable analyses, the independent risk factors for AKI were body mass index (odds ratio [OR] 1.03; 95% confidence interval [CI] 1.00 to 1.06), hyperlipidemia (OR 2.53; 95% CI 1.21 to 5.28), and preoperative use of ACE-I or ARB (OR 2.06; 95% CI 1.05 to 4.04). The postoperative mortality was 0.45% (n = 2), both of whom had AKI. Duration of hospitalization was greater in patients with AKI versus no AKI (4.0 versus 2.7 d; P = 0.0003). Postoperative AKI is not infrequent after gastric bypass surgery. Certain comorbid conditions and their commonly prescribed treatments, ACE-I or ARB, are independently associated with increased risk for postoperative AKI.