Acute kidney injury following bariatric surgery

Background: Postoperative acute kidney injury (AKI) following bariatric surgery has not been well studied. The aim of this study is to identify factors associated with risk of AKI. Methods: The medical records of adult patients who underwent bariatric surgery between March 1, 2005 and March 31, 2011 at the Mayo Clinic were reviewed to identify patients who experienced AKI, defined as postoperative increase in serum creatinine (sCr) by 0.3 mg/dL within 72 h. For each AKI case, two controls were matched for surgical approach (laparotomy vs. laparoscopic). A chart review was conducted and conditional logistic regression analyses were performed to identify risk factors for AKI. Results: There were 1,227 patients who underwent bariatric surgery, and of these, 71 developed AKI (5.8 %). The median sCr increase was 0.4 (interquartile range 0.3-0.6) mg/dL. Independent patient factors associated with increased risk included higher body mass index [odds ratio (OR) 1.24, 95 % CI 1.06-1.46 per 5 unit increase, P = 0.01] and medically treated diabetes mellitus (OR 2.77, 1.36-5.65, P = 0.01). Patients experiencing AKI had higher rates of blood transfusions (P < 0.01), postsurgical complications (P < 0.01), and longer hospital stays (P < 0.01). Another 30 patients developed kidney injury after 72 postoperative hours, usually in the setting of dehydration. Conclusions: Kidney injury following bariatric surgery is not uncommon and is associated with higher body mass index and diabetes. Further, there should be a high risk of suspicion for kidney injury in postoperative patients developing volume depletion.