The Effect of Body Mass Index on Stone-Free Rate and Operative Complication Rate of Percutaneous Nephrolithotomy

Abstract

Objective: To study the effect of body mass index (BMI) on percutaneous nephrolithotomy (PCNL) stone-free rate and operative complication rate. Materials and Methods: Retrospective cohort study included patients who underwent PCNL from January 2005 till December 2007. All were stratified according to world health organization BMI classification (normal, overweight, obese, morbidly obese) into the effect of BMI on PCNL stone-free rate and operative complications including bleeding, transfusion, septicemia, intensive care unit admission and urinary leak. Results: Totally 70 patients were included in our study with mean age of 42 years, male to female ratio 5:1, and 68.2% of them had no comorbid factors while 11.6% with diabetic, 9.3% with hypertensive, and 4.7% having both and 15.5% having the history of previous pyelolithotomy. Most of the patients (94.3%) had performed intravenous pyelogram preoperatively, in which 7% showed anomalous kidney (horseshoe, malrotated), 44% staghorn and 42% pelvic stones > 2 cm in size. The indications for PCNL in our study group were staghorn stone in 41.4%, failed extracorporeal shock wave lithotripsy in 14.3%, large stones > 2 cm in 44.3%. The operative success rate was 87.1%. When we stratified our patients according to the world health organization BMI, 28.6% were normal BMI, 37.1% overweight and 34.3% obese. Multiple regression analysis revealed that increasing BMI do influence the operative risk of bleeding, transfusion, leak, intensive care unit admission, sepsis with significant p = 0.026 (CI 8.7–0.59) and inversely influence the stone-free rate with p = 0.017 (CI 0.012–0.64). Conclusion: Obese patients have higher operative complication risk and low stone-free rate on PCNL.