Extracorporeal shock wave lithotripsy for lower calyceal stones: can clearance be predicted?

To determine the influence of pelvicalyceal angle, size of the lower calyx infundibulum and lowerpole calyceal anatomy in predicting the clearance of fragments after extracorporeal shock wave lithotripsy (ESWL) for lower calyceal stones.

The study comprised a retrospective analysis of 133 patients, divided into 92 who were considered to be completely clear of fragments 6 months after ESWL and 41 who had residual stones. The pelvicalyceal angle, diameter of the lower calyx infundibulum and lower-pole calyceal pattern were determined from intravenous urograms.

There were residual stones in 64% of the patients with a pelvicalyceal angle < 90 degrees, in 12% of those with an angle > 90 degrees, in 70% of patients with an infundibular diameter < 4 mm, in 16% of those with a diameter > 4 mm, in 78% with a complex calyceal pattern and 12% with a simple calyceal pattern.

These three anatomical factors play a key role in predicting the clearance of stone and they should be assessed during intravenous urography to facilitate the planning of treatment for lower calyceal stones.