title: Outcomes of percutaneous nephrolithotomy stratified by body mass index.
abstract: BACKGROUND
  Obesity places surgical patients at a greater risk of complications. The effects of obesity on outcomes and complications from percutaneous nephrolithotomy (PCNL) are not well defined.
  
  
  OBJECTIVE
  The objective of this study was to stratify outcome and morbidity of PCNL with respect to body mass index (BMI) in a large contemporary series.
  
  
  METHODS
  The charts of 234 patients who underwent PCNL were reviewed retrospectively. Patients were divided into four groups depending on their BMIs: ideal body weight (IBW) <25 kg/m(2), overweight 25 to 29.9 kg/m(2), obese >or=30 to 34.9 kg/m(2), and morbidly obese >or=35 kg/m(2). Kidney stone diameter was measured on preoperative computerized tomography scans. Hemorrhage was estimated using hematocrit. Univariate analysis was performed with respect to hospital length of stay (HLOS), stone size, complication rate, hemorrhage, and stone-free rate.
  
  
  RESULTS
  Of the 234 patients undergoing PCNL (mean age, 54.3 +/- 13.6 years; 54% male), height and weight data were available for 187 (80%) with a mean BMI of 29.3 +/- 8.0 (range 14.1-57.2); 38 (20.3%) were morbidly obese, 43 (23%) obese, 45 (24.1%) overweight, and 61 (32.6%) were within or below their IBW. Mean stone sizes were comparable: 3.9 +/- 2.0 cm (morbidly obese), 3.7 +/- 2.0 cm (obese), 3.1 +/- 1.4 cm (overweight), and 3.6 +/- 1.9 cm (IBW). Mean HLOS (days) was similar between groups: 2.6 +/- 1.7 (morbidly obese), 2.8 +/- 2.0 (obese), 2.5 +/- 1.2 (overweight), and 3.4 +/- 4.7 (IBW). The largest interval decreases in hematocrit (mg/dL) were also comparable: 5.3 +/- 3.8 (morbidly obese), 5.9 +/- 4.3 (obese), 7.2 +/- 4.1 (overweight), and 6.2 +/- 4.3 (IBW). Using strict imaging criteria, the overall stone-free rate was 80%. No statistically significant differences among the three groups were seen with respect to HLOS, stone-free rate, complication rate, or change in hematocrit when stratified by BMI.
  
  
  CONCLUSIONS
  Stone-free rate, complication rate, hemorrhage, and HLOS are independent of BMI in a retrospective review of patients undergoing PCNL.
authors.affiliation: Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA. tomaszewskijj@upmc.edu
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Tomaszewski
authors.forename: Marc C
authors.initials: MC
authors.lastname: Smaldone
authors.forename: Tina
authors.initials: T
authors.lastname: Schuster
authors.forename: Stephen V
authors.initials: SV
authors.lastname: Jackman
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Averch
mesh_terms: D015992:Body Mass Index; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009403:Nephrostomy, Percutaneous / Q000379:methods*; D016896:Treatment Outcome