PCNL trajectory to predict success in supine PCNL: a novel concept

Abstract

INTRODUCTION: Supine PCNL confers certain advantages over prone. Access parameters change with positioning. Supine position limits maneuverability of instruments, limiting access to upper & mid-pole stones. We aim to determine predictive factors for success of supine PCNL through road-mapping of PCNL trajectory. MATERIAL & METHOD: Consecutive patients undergoing PCNL from July-Dec2010 were recruited. Choice of position was made by surgeon. Tracts were performed under USG & fluoroscopy. Distances and angles were measured intra-operatively with rigid and flexible nephroscope, and correlated with pre-operative imaging. RESULTS 19 patients underwent PCNL(13supine, 6prone) Stone load was comparable in both groups. Overall stone clearance after single PCNL was 74%. Regardless of abdominal thickness and approach, all lower pole and renal pelvic stones were reached with mean excursion of 140 mm in supine & 105 mm in prone position. Mean entry angle was 59 for supine, and 35 for prone. In supine PCNL, the upper pole was reached in 4 of 11 tracts, with mean-excursion of 172mm& entry angle of 33. Similarly, 2 of 11 supine PCNL reached middle pole. Conversely, all prone PCNL tracts reached upper & middle pole with decreased excursion & angle. CONCLUSION: PCNL in prone position can reach renal pelvis and 3 poles via lower pole puncture. PCNL trajectory may be a tool to predict success in supine PCNL by estimating chance of reaching mid & upper pole. Skin to upper pole distance larger than 185mm and entry angle more than 48 degrees decrease chance of upper pole access.