Inferior pole collecting system anatomy: its probable role in extracorporeal shock wave lithotripsy.

In addition to the gravity-dependent position, we believe that other particular anatomical features may be important in the retention of stone debris in the lower calices after extracorporeal shock wave lithotripsy (ESWL). We analyzed the inferior pole collecting system anatomy in 146, 3-dimensional polyester resin corrosion endocasts of the pelviocaliceal system. The inferior pole was drained by multiple calices disposed in 2 rows in 56.8% of the cases and by 1 midline caliceal infundibulum in 43.2%. In 60.3% of the cases there was a lower infundibulum equal to or greater than 4 mm. in diameter and 39.7% had a lower infundibulum smaller than 4 mm. in diameter. In 74.0% of the cases an angle of greater than 90 degrees was formed between the lower infundibulum and the renal pelvis, and in 26.0% the angle was 90 degrees or smaller. We believe that the physician should consider these anatomical features when suggesting ESWL to treat calculi in the lower calices.