Ureterolithiasis: value of the tail sign in differentiating phleboliths from ureteral calculi at nonenhanced helical CT.

Abstract

To determine the value of the tail sign in differentiating phleboliths from ureteral calculi at nonenhanced helical computed tomography (CT). The nonenhanced helical CT scans in 82 patients with a confirmed diagnosis of pelvic ureterolithiasis were retrospectively reviewed. Each calcification along the ureter was classified as a phlebolith or a ureteral calculus on the basis of clinical and imaging findings and was analyzed for the presence of a tail sign. Eighty-two patients each had a single ureteral calculus. None of these calculi were associated with a positive tail sign. Sixty-nine phleboliths were present in 35 patients. Forty-five phleboliths (65%) were associated with a positive tail sign. Of the remaining 24 phleboliths, 17 (25%) were associated with a negative tail sign and seven (10%) were indeterminate. The tail sign has a sensitivity of 65% (45 of 69; 95% CI: 53%, 75%) and a specificity of 100% (82 of 82; 95% CI: 96%, 100%) in differentiating phleboliths from ureteral calculi. The tail sign is an important indicator that a suspicious calcification represents a phlebolith. Absence of the tail sign indicates that the calcification remains indeterminate.