Impact of body mass index on clinical outcomes associated with percutaneous nephrolithotomy.

Introduction: Percutaneous nephrolithotomy (PCNL) is the preferred treatment for patients with large renal calculi or stones that have not responded to extracorporeal shock wave lithotripsy (ESWL). The objective of this study was to compare outcomes and complications of PCNL in patients of various body mass indices (BMI) to determine the safety of this procedure in patients with elevated BMI. Methods: A retrospective chart review of 114 patients who underwent PCNL between 2006 and 2009 was performed. Patients were separated into 4 groups with respect to their BMI: (1) ideal bodyweight (BMI <25 kg/m2), (2) overweight (BMI 25-29 kg/m2), (3) obese (BMI 30-39 kg/m2) and (4) morbidly obese (BMI ≥40 kg/m2). One-way ANOVA and univariate logistic regression analysis were used to assess the association between BMI (classified into 4 levels) and variables including age, sex, stone size, length of stay, incidence of complications and stone-free rates. Results: The distribution of the 114 patients in each BMI category was: ideal body weight 39 (34%), overweight 24 (21%), obese 41 (36%), morbidly obese 10 (9%). There was no difference in the composition of groups with respect to age, sex, pharmacologically treated comorbidities or stone size. Mean length of stay in days, intra- and postoperative complication rates were not statistically different. Stone-free rates showed no significant difference between groups: 90% ideal body weight; 87% overweight; 90% obese; 80% morbidly obese (p = 0.83). Interpretation: Outcomes of PCNL were statistically independent of BMI. PCNL is a safe and efficacious treatment of stone disease in patients of all sizes.