Useful prediction of ureteral calculi visibility on abdominal radiographs based on calculi characteristics on unenhanced helical CT and CT scout radiographs.

AIMS: To determine whether visibility of ureteral calculi on plain radiographs of the kidney, ureter and bladder (KUB) could be predicted based on characteristics on unenhanced helical computed tomography (UHCT) and CT scout radiographs (CTSR).
METHODS: One hundred and twenty-three patients diagnosed with 140 ureteral calculi on UHCT, had undergone both UHCT and KUB within 24 h and before calculus passage or intervention were included. The visibility of ureteral calculi on KUB and CTSR as well as their sizes, locations and densities on UHCT were recorded. The association of CTSR/UHCT characteristics of ureteral calculi and their visibility on KUB were analysed. Multivariate analyses using logistic regression were computed as predictors for visibility on KUB.
RESULTS: Of the 140 calculi, 56 (40%) and 98 (70%) were visible on CTSR and KUB respectively. All calculi detectable on CTSR were also visible on KUB. Multivariate analyses of the 84 CTSR undetectable calculi revealed that non-middle ureteral location and higher calculi densities on UHCT were significant predictors of visibility on KUB. All non-middle ureteral calculi with density > 800 Hounsfield units (HU) were visible on KUB. Of 23 calculi in the middle ureter or with density < 200 HU, 17 (74%) were invisible on KUB.
CONCLUSIONS: Ureteral calculi characteristics on UHCT and CTSR are useful for predicting their visibility on KUB. Patients with visible calculi on CTSR or non-middle ureteral calculi with density > 800 HU are suitable for KUB to follow-up calculi status.