BACKGROUND: Stone volume and ureteral dilation are parameters which are useful in planning intracorporeal lithotripsy (ICL). The current study was designed to examine the differences in ureteral dilation and calculus size between obstructing proximal and distal ureteral stones.
METHODS: Institutional review board approval was obtained prior to initiation of the study. A retrospective review was performed for 177 consecutive patients with obstructing ureteral calculi in whom computed tomography (CT) imaging was available. Proximal ureteral calculi were located above the iliac vessels and distal calculi were below. Ureteral axial dilation was measured one CT cut (2.5 mm or 5mm) above the calculus. Measurements were made using the highest magnification possible for CT scan images. Statistical analysis was performed using student’s t-test.
RESULTS: 65 proximal and 111 distal ureteral calculi were analyzed. Proximal location was associated with a greater degree of ureteral axial dilation (mean 6.1mm versus 5.3mm, p=0.01) and greater calculus coronal length (mean 9.9mm versus 8.3mm, p=0.005) than distal location. There was no statistical difference in axial calculus diameter for proximal and distal stones (mean 5.3mm versus 5.0mm, p=0.29). These are shown in table 1. For proximal calculi, 71% were associated with < 7mm dilation, 25% were associated with 7-10mm dilation, and 4% were dilated > 10mm. For distal calculi, 89% were associated with < 7mm dilation, 7% were associated with 7-10mm dilation, and 4% were dilated > 10mm. Coronal diameter was the largest measured diameter in 94% of calculi and mean coronal diameter was significantly greater than mean axial diameter (8.9mm versus 5.1mm, p < 0.001).
CONCLUSIONS: Obstructive proximal ureteral calculi are associated with a significantly greater degree of ureteral dilation and larger coronal stone length than distal calculi. These findings should guide the endoscopist in planning intracorporeal ureteroscopic lithotripsy treatments and choosing appropriate ureteral occlusive devices. We suggest obtaining CT coronal images to more accurately characterize obstructing ureteral stones.

	Proximal Ureter	Distal Ureter	P value
Ureteral Dilation (mm)	6.1	5.3	0.01
Coronal Stone length (mm)	9.9	8.3	0.005
Axial Stone Diameter (mm)	5.3	5.1	0.29