The impact of body mass index on renal functional outcomes following minimally invasive partial nephrectomy.

Abstract

To assess the impact of body mass index (BMI) on perioperative and renal functional outcomes in patients undergoing minimally invasive partial nephrectomy (MIPN). In our IRB-approved, prospectively maintained clinical database, we identified 1206 patients who underwent kidney surgery from 2002 to 2013. Estimated glomerular filtration rate (eGFR) was obtained at baseline and each follow-up visit. From this group, patients who underwent MIPN with more than 12 months of follow-up were selected. Patients were separated into 4 cohorts based on BMI: normal weight (<25 kg/m(2)), preobese (25-30 kg/m(2)), obese class 1 (30-35 kg/m(2)), and obese class ≥2 (>35 kg/m(2)). Change in eGFR was compared across demographic and clinical variables through linear and logistic regression models. A total of 235 patients met inclusion criteria with median follow-up of 29 months (interquartile range [IQR] 19, 45). There were no differences in demographic, perioperative, or pathologic features between BMI groups. While controlling for gender, race, Charlson comorbidity score, tumor size, and ischemia time, obese class 1 (odds ratio [OR] 4.68, p=0.019), obese class ≥2 (OR 4.27, p=0.033), and age (OR 1.06, p=0.014) were associated with increased risk of CKD stage ≥3; however, higher baseline eGFR (OR 0.91, p<0.001) was associated with a reduced risk of CKD stage ≥3. While controlling for the same variables, increasing BMI was associated with a significant absolute reduction in eGFR at 1 year (0.38 mL/minute/1.73 m(2) reduction in GFR per 1 kg/m(2) increase in BMI, p=0.009). MIPN is technically feasible in obese patients with similar perioperative outcomes to nonobese patients. BMI is an independent risk factor for worsening kidney function following MIPN.