The Impact of Obesity in Patients Undergoing Robotic Partial Nephrectomy

As the prevalence of obesity increases worldwide, an increasing proportion of surgical candidates have an elevated body mass index (BMI), with associated metabolic syndrome. Yet there exists limited evidence regarding the effect of elevated BMI on surgical outcomes in robotic surgeries. We examined whether obese patients had worse perioperative outcomes and postoperative renal function after robotic partial nephrectomies (RPNs). We performed a multi-institutional analysis of 1770 patients who underwent RPNs between 2008 and 2015, allowing time for the data set to mature. Associations between BMI, as a continuous and categorical variable, and perioperative outcomes, acute kidney injury (AKI, >25% reduction in estimated glomerular filtration rate [eGFR]) at discharge, and change in eGFR per month were analyzed. AKI and eGFR were evaluated using multivariable logistic and linear regression models adjusted for confounders, including age, Charlson comorbidity index, tumor size, and the identity of the surgeon. In total 45.2% (n = 529) of patients were found to be obese, with a greater prevalence of hypertension and diabetes in overweight and obese patients. Obese patients were more likely to have malignant tumors (>77% vs 68%, p < 0.001) and trended toward having larger tumors (3.0 cm vs 2.8 cm; p = 0.061). Heavier patients required longer operative times (166-196 minutes vs 155 minutes; p < 0.001), although equivalent warm ischemia times (p = 0.873). Obesity did not correlate with an increased complication rate (p > 0.05). On multivariable analysis, obesity (odds ratio [OR] = 1.81; p = 0.031), male sex (OR = 1.54; p = 0.028), and larger tumor size (OR = 1.23; p < 0.001) were associated with a significant increase in the likelihood of AKI at discharge. BMI above normal weight was not associated with greater eGFR decline per month post-RPN. Obesity was associated with equivalent perioperative outcomes and long-term renal function. Further research is warranted into how obesity and metabolic syndrome may foster a more aggressive tumor environment. RPN appears to be an equally safe operative option for patients regardless of obesity status.