Do anatomic factors pose a significant risk in the formation of lower pole stones?

To determine whether various anatomic factors predispose to a lower pole stone on one side compared with the other.

We analyzed the intravenous urography pictures of 40 consecutive patients presenting with a single lower pole stone. Measurements were taken of the infundibulopelvic angle (IPA), ureteroinfundibular angle, infundibular width, pelvicaliceal height, infundibular length, and pelvicaliceal angle of the affected and normal kidney. The IPA was measured according to the methods of Sampaio, Bagley, and Elbahnasy. A comparison was made to determine whether any of these measurements predisposed one side to form stones.

The mean age was 47 years (range 20 to 80). The mean stone size was 9.2 mm (range 5 to 20). The mean IPA was 94.82 degrees (Sampaio), 56.17 degrees (Bagley), 60.40 degrees (Elbahnasy), and 49.15 degrees (Sampaio) on the affected kidney and 95.97 degrees (P = 0.66), 57.47 degrees (P = 0.57), 65.9 degrees (P = 0.04), and 54 degrees (P = 0.07) on the normal side. A statistically significant difference was found only when we measured the IPA as described by Elbahnasy. The mean infundibular width was 4.4 mm on both sides (P = 0.99). The caliceopelvic height was 21.6 mm on the affected side and 22.6 mm on the normal side (P = 0.30). The infundibular length was 28.6 mm and 27.4 mm (P = 0.16) and the caliceopelvic angle was 48 degrees and 47.6 degrees (P = 0.8) on the affected and normal kidneys, respectively

Lower pole anatomy as a risk factor for stones depends on the type of measurement used. A consensus should be reached to define how exactly the IPA should be measured. Other anatomic factors were not significantly different between the affected and normal side in our study.