Differences in Stone Size and Ureteral Dilation Between Obstructing Proximal and Distal Ureteral Calculi

Abstract

To examine the differences in ureteral dilation and calculus size between obstructing proximal and distal ureteral stones. A retrospective review of computed tomography (CT) scans from 176 consecutive patients with obstructing ureteral calculi was performed. For the calculi, the axial diameter was defined as the largest stone diameter on the axial CT images, and the coronal length was defined as the cephalocaudal length of the stone measured on the coronal CT images. Univariate and multivariate statistical analyses were performed. A total of 65 proximal and 111 distal ureteral calculi were analyzed. On univariate analysis, the proximal calculi were associated with a greater degree of ureteral dilation (mean 6.1 mm vs 5.3 mm, P = .01) and had a greater coronal length (mean 9.9 mm vs 8.3 mm, P = .005) than distal calculi. This association was also true on the multivariate analysis, which controlled for age and sex (P = .0004). No statistically significant difference was found in the axial calculus diameter for the proximal and distal stones (mean 5.3 mm vs 5.0 mm, P = .29). In a subset of 50 patients whose contralateral ureters (without stones) were measured for control comparison, the ureteral dilation in the ureters with stones was significantly greater than in the control ureters (proximal ureter 6.2 mm vs 4.3 mm, P = .001; distal ureter 4.7 mm vs 3.8 mm, P = .004). For proximal calculi, 72.3% were associated with ureteral dilation of less than 7 mm, 23.1% with 7-10 mm, and 4.6% with greater than 10 mm. For the distal calculi, 90.1% were associated with ureteral dilation of less than 7 mm, 6.3% with 7-10 mm, and 3.6% with greater than 10 mm. The coronal length was the largest measured diameter in 94% of the calculi, and the mean calculus coronal length was significantly greater than the mean axial diameter (8.9 mm vs 5.1 mm, respectively, P < .001). The results of our study have shown that proximal ureteral calculi are associated with a significantly greater degree of ureteral dilation and larger coronal length than are distal calculi. These findings should guide the endoscopist in planning intracorporeal ureteroscopic lithotripsy. We suggest obtaining CT coronal images to more accurately characterize obstructing ureteral stones.