Deirdre Coll MBBCh, PRESENTER: Nothing to Disclose

Abstract: HTML Purpose: Severity of perinephric stranding and perinephric fluid correlate directly with degree of obstruction and likelihood of spontaneous stone passage. The traditional teaching has been that very small stones (1 mm or smaller) would pass spontaneously and not cause significant obstruction, perinephric fluid or perinephric stranding. This study correlates stone size with degree of obstruction. { Methods and Materials: 226 consecutive patients with ureteral stones underwent unenhanced CT. For each patient, we determined stone size, location and graded perinephric stranding and the amount of perinephric fluid as none, mild, moderate or severe. Results: Percentage of patients with stones <1 mm, 2 to 4 mm, or >4 mm in size with moderate/severe perinephric fluid was 32%, 18 % (p<0.05), and 13% (p<0.02) respectively. Percentage of patients with stones <1 mm, 2 to 4 mm in size, or >4 mm in size that showed moderate or severe perinephric stranding was 44%, 34%, and 38% respectively. These differences were not statistically significant. Furthermore, 86% of stones <1 mm but only 48% of stones >1 mm were lodged in the distal ureter or at the UVJ at time of diagnosis. Conclusion: Ureteral stones that measure <1 mm in size can cause severe obstruction. While this seems paradoxical, we postulate that it is related to the fact that tiny stones can have an irregular surface when compared to larger stones. These tiny stones typically lodge in the distal ureter or at the UVJ and the resultant wall edema then causes high-grade obstruction.      

Coll MBBCh, D, Correlation of Stone Size and Degree of Obstruction on Unenhanced CT.  Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL. http://archive.rsna.org/2003/3106817.html