Impact of lower pole renal anatomy on stone clearance after shock wave lithotripsy: Fact or fiction?

Purpose: We determined whether there is a significant relationship between the spatial anatomy of the loser pole on preoperative excretory urography and stone fragment clearance after shock wave lithotripsy, Materials and Methods: The anatomical factors affecting lower pole stone clearance after shock wave lithotripsy were evaluated retrospectively in 108 patients. Stone-free status was assessed by renal computerized tomography with or without renal ultrasound. The stone-free rate at 3 months was correlated with lower pole infundibular length and width in mm. as well as with the lower pole infundibulopelvic angle in degrees. The statistical significance of each lower pole anatomical factor as well as other stone, renal and treatment factors were correlated with the stone-free rate using the Mann-Whitney and chi-square tests. Results: Three months after shock wave lithotripsy 79 patients (73.1%) were free of stones. Mean lower infundibular length plus or minus standard deviation was 20.9 +/- 6.56 mm., mean infundibular width was 5.65 +/- 2.34 mm, and the mean lower pole infundibulopelvic angle was 48.33 +/- 14.84 degrees. In 49 (45.4%) and 59 (54.6%) patients infundibular length was greater than 3 cm, and 3 cm. or less, respectively. Infundibular width was greater than 5 mm. and 5 mm. or less in 45 (41.7%) and 63 (58.3%) patients, respectively. No obtuse infundibulopelvic angles were noted. None of the 3 lower pole anatomical factors had any significant impact on the stone-free rate at 3 months, Renal morphology was the only factor significantly affecting the stone-free rate since stone clearance was significantly less in pyelonephritic kidneys (p = 0.0009). Conclusions: Differences in the intrarenal anatomy of the lower pole have no significant impact on stone clearance after shock wave lithotripsy. Further examination of the lower pole renal anatomy with a search for other contributing factors is still warranted.