title: The impact of body mass index on renal functional outcomes following minimally invasive partial nephrectomy.
abstract: OBJECTIVE
  To assess the impact of body mass index (BMI) on perioperative and renal functional outcomes in patients undergoing minimally invasive partial nephrectomy (MIPN).
  
  
  METHODS
  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.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: 1 Section of Urology, Department of Surgery, The University of Chicago Medical Center , Chicago, Illinois.
authors.forename: Kyle A
authors.initials: KA
authors.lastname: Richards
authors.forename: Edris
authors.initials: E
authors.lastname: Negron
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Cohn
authors.forename: Zoe
authors.initials: Z
authors.lastname: Steinberg
authors.forename: Scott E
authors.initials: SE
authors.lastname: Eggener
authors.forename: Arieh L
authors.initials: AL
authors.lastname: Shalhav
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000704:Analysis of Variance; D015992:Body Mass Index; D015897:Comorbidity; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate / Q000502:physiology; D006801:Humans; D007680:Kidney Neoplasms / Q000150:complications / Q000503:physiopathology / Q000601:surgery*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures; D009392:Nephrectomy / Q000379:methods*; D009765:Obesity / Q000150:complications* / Q000503:physiopathology; D011446:Prospective Studies; D051436:Renal Insufficiency, Chronic / Q000209:etiology / Q000503:physiopathology*; D012189:Retrospective Studies; D012307:Risk Factors