Pd45-03 Surgical Algorithm for Encrusted Ureteral Stent Removal Using the Kidney, Ureter, and Bladder (Kub) Grading System

Abstract

INTRODUCTION AND OBJECTIVES: Stone size is thought to be an important factor in the appropriate management of nephrolithiasis and counseling of patients. The typical quantification of stone size is based on a linear measurements on computed tomography (CT) imaging, but volumetric analysis has become more readily available and relevant in recent times. While discussions regarding the most accurate ways to analyze stone volume are currently ongoing, our study aims to further investigate the utility of volume measurement in the treatment of renal calculi.METHODS: A retrospective review of patients undergoing percutaneous nephrolithotomy (PCNL) between 2009 and 2013 was performed. Preoperative and postoperative helical CT images were used to measure stone size, location, and density; iPlan CMF software was used to reconstruct three-dimensional models from the aforementioned CT scans and calculate volume measurements. Logistic regression and correlational analysis was performed to evaluate the relationship between stone volume and linear measurements, and to identify predictors of postoperative percent-reduction in stone volume and stone-free rate.RESULTS: The analysis included a total of 175 patients undergoing first-look PCNL for solitary stones, regardless of size, shape, and location within the kidney; patients with ureteral stones were excluded. Stone volume was most correlated with linear measurements in the sagittal dimension (r ¼ 0.85, p < 0.05), but axial (r ¼ 0.82) and coronal (r ¼ 0.81) measurements were not far behind. Preoperative stone volume was positively correlated to postoperative stone volume (r ¼ 0.36, p < 0.05). There was no significant difference in postoperative stone volume reduction based on stone size, location, or density.CONCLUSIONS: In patients undergoing PCNL, volumetric stone measurement using three-dimensional reconstruction correlates positively with linear measurements and, therefore, does not significantly change or augment our understanding of a patient's stone burden.