Limited field noncontrast computerized tomography for followup of ureteral stones: initial results.

Abstract

Due to high specificity and sensitivity noncontrast computerized tomography is increasingly used to diagnose and follow patients with ureteral stones. We evaluated the feasibility of limited field noncontrast computerized tomography to follow patients with ureteral stones. Included in the study were 71 patients who underwent diagnostic and followup noncontrast computerized tomography due to ureteral stones. According to stone position on the first diagnostic scan a limited field batch from the followup scan was formed and examined by an independent radiologist. Radiation doses and rates of potentially missed findings in the batch were compared to those of the full followup noncontrast scan. Average full followup noncontrast computerized tomography length was 46.5 cm and average batch length was 20.7 and 13.8 cm for proximal and distal stones, respectively. The average full followup noncontrast scan radiation dose was 12.2 mSv. Average batch doses were 6.1 and 4.1 mSv for proximal and distal stones, respectively (p = 0.002), resulting in a radiation exposure reduction of 48.8% for proximal stones and 66% for distal stones. In 3 cases additional clinical information (not including hydronephrosis) was missed when relying only on batch images. This additional information did not impact further urological treatment. Limited field noncontrast computerized tomography is a feasible option for following patients diagnosed with ureteral stones. It may lead to significantly lower radiation exposure.