Outcome of Percutaneous Surgery Stratified According to Body Mass Index and Kidney Stone Size

Abstract

To stratify outcome and morbidity of percutaneous nephrostolithotomy (PCNL) with regard to body mass index (BMI) and kidney stone burden. The charts of 148 patients who underwent PCNL procedures were reviewed retrospectively. Hospital stay, blood loss, maximal temperature during inpatient stay, and stone-free outcomes were evaluated. Patients were divided into 3 groups depending on their BMIs: <25 kg/m, 25 to 29.9 kg/m, and >30 kg/m. Kidney stone burden was measured in terms of square area in millimeters, as measured by retrospective review of computerized tomography scans. Preoperative computerized tomography scan for measurement of stone burden was available for only 85 patients who are included in the study. Analysis of variance for a single variable was performed with regard to the values of the hospital stay, postoperative maximal temperature, and hemoglobin change. Of the 85 patients, 37 (43.5%) were obese or morbidly obese (BMI, >30 kg/m), 33 (38.8%) were overweight (BMI, 25 to 29.9 kg/m), and 15 (17.7%) were within or below their ideal weight (BMI, <25 kg/m). No statistically significant difference among the 3 groups was seen for stone-free rate, postoperative fever, or change in hemoglobin when stratified by BMI alone or by BMI and kidney stone burden. However, significantly longer length of stay for the group with BMI <25 kg/m was observed when stratifying either by BMI alone (P=0.01) or by BMI and kidney stone burden (P=0.03). In this retrospective review of patients with kidney stones undergoing PCNL, the stone-free outcome and associated morbidity of PCNL (except for the length of hospital stay) is independent of both patients' BMI and stone burden when stratifying by commonly defined parameters.