Site of impaction of ureteric calculi requiring surgical intervention.

Textbooks describe three narrowest anatomic sites in the ureter as the most likely places for ureteral calculi to lodge, these are: the pelvi-ureteric junction (PUJ), the point where the ureters cross over the iliac vessels and the ureterovesical junction (UVJ). The purpose of this study is to determine whether calculi causing ureteric obstruction and requiring surgical treatment are found mostly at these three narrowest anatomic points of the ureter. Three hundred consecutive patients with impacted ureteric calculi who required surgical intervention were studied. The location of the impacted calculus on the day of surgical intervention was categorized according to nine predetermined levels outlined in a designed diagram based on findings on non-contrast CT of kidneys, ureters and bladder. Two peaks in stone distribution in the ureters were encountered; the first was above the ischial spine in the proximal part of the lower third ureter (84 patients, 28%), while the second was at the level between L3 and L4 lumbar vertebrae (66 patients, 22%). Overall, the location of impacted calculi was as follows, 53, 34, 10 and 3% in the lower third ureter, upper third ureter, PUJ and mid ureter, respectively. This study demonstrates two peaks of calculi distribution in the ureter where ureteric calculi become impacted: the upper ureter below the PUJ and a second in the lower ureter, more proximal than the UVJ. There was an absence of the peak in stone location over the iliac vessels, that is, the mid ureter.