Obesity: An Independent Predictor of Acute Renal Failure After General Surgery

Background Half of Americans will have obesity, and a quarter will have severe obesity by the year 2030. Postoperative acute renal failure (ARF) is associated with increased morbidity and mortality. Given the increase in the number of patients with obesity undergoing elective surgery, we investigated the relationship between obesity and postoperative ARF after elective general surgery procedures. Methods We performed a retrospective cohort study of patients in the 2015-2019 National Surgical Quality Improvement Program database who underwent elective general surgery procedures. The primary outcome was the presence of postoperative ARF. The patient body mass index (BMI) was categorized as normal (BMI 18.5-24.9), overweight (BMI 25-29.9), obesity class 1 and 2 (BMI 30-39.9), severe obesity (BMI 40-49.9), and extreme obesity (BMI³50). Descriptive statistics and unadjusted comparisons were performed for patients who developed postoperative ARF and those who did not. Multivariable regression analyses were used to model BMI categories and postoperative ARF, adjusting for patient- and surgical-level covariates. Results Among 424,527 patients included in the study, 3638 patients (0.8%) developed ARF. Patients who developed ARF were older, had a higher BMI, and had more serious comorbidities. After risk adjustment, there was a stepwise rise in odds of developing postoperative ARF with increasing BMI categories compared to normal BMI: (overweight: OR 1.11 (95% CI 1.0-1.23), obesity class 1 and 2: OR 1.32 (95% CI 1.2-1.46), severe obesity: OR 1.45 (95% CI 1.27-1.66), and extreme obesity: OR 1.78 (95% CI 1.47-2.15)). Conclusion Obesity is independently associated with ARF after elective general surgery procedures.