Effect of variation in the anatomy of the pelvi-calyceal system on the success of percutaneous nephrolithotomy-A step ahead

摘要

The anatomic properties of the pelvi-calyceal system (PCS) play a role in stone formation and on the success of minimally invasive procedures. [1] The relationshipbetween the PCS anatomy and the success of endourologic procedures, like shock-wave lithotripsy and retrograde intrarenal lithotripsy, has been reported. [2]Though stone size and staghorn type are established independent factors affecting the success of percutaneous nephrolithotomy (PCNL), [3] the PCS anatomy is oneof the most neglected aspects of endourologic stone removal and there are no studies till date to report PCS anatomical factors that may affect the success rates ofPCNL. The relationship of PCS' anatomic properties like infundibulopelvic angle (IPA), upper-lower calix angle (ULA), infundibular length (IL), infundibular width(IW), PCS surface area (PCS-SA),degree of hydronephrosis and PCS type to the success of PCNL have been evaluated for the first time in this present retrospectivestudy.The most widely accepted PCS classification system given by Sampaio et al.,[4] classifies PCS into A 1 , A 2 , B 1 and B 2 . IPA is the inner angle formed at theintersection of the ureteropelvic and central axes of the lower pole infundibulum; ULA is the angle between the central axes of the upper and lower pole infundibula; ILis the distance from the most distal point at the bottom of the calyx to which access was performed to the midpoint of the lower lip of the renal pelvis and IW is thewidest point along the infundibula in which access was made. Grid technique was used to calculate PCS surface area.Preoperative intravenous urography (IVU) was done to delineate PCS anatomy while postoperative X-ray KUB and either IVU or CT were done to document stoneclearance. Out of the 493 PCNL performed, 389 (78.1%) were successful (Group 1) and 109 (21.9%) were unsuccessful (Group 2) and anatomic factors werecompared between both groups. While both groups were similar with respect to age, sex distribution and body mass index, mean stone size was 7.1 cm 2 vs. 9.2 cm2 in the respective groups.The PCNL success rate for PCS Type A 1 , A 2 , B 1 , and B 2 was 79.5%, 82.0%, 74.3%, and 80.3%, respectively. Forward stepwise regression analysis showedthat PCS-SA was the only independent factor that affected the PCNL success rates. Other anatomical factors were not found to be significantly different among bothgroups. The best cutoff point for the PCS-SA in predicting the success of PCNL was 20.5 cm 2 and patients with a PCS-SA of <20.5 cm 2 were 1.96 times morelikely to undergo successful PCNL.