Can computed tomography scout radiography replace plain film in the evaluation of patients with acute urinary tract colic?

PURPOSE: To determine the sensitivity of computed tomography (CT) scout view in detecting ureteral stones and whether CT scout radiography can replace plain film in the evaluation of patients with acute urinary tract colic.
MATERIAL AND METHODS: Between January 2000 and 2002, 110 patients with ureterolithiasis were prospectively evaluated for the detection of ureteral stones on CT scout radiographs. The findings were compared with those of plain films. All patients were examined with plain film, CT scout radiography, and unenhanced helical CT. CT scans were performed within 24 h of plain films. Each CT scout radiograph was interpreted without knowledge of the findings on plain film.
RESULTS: 111 stones were detected by unenhanced helical CT. Mean stone size was 3.9 mm (range 1-10 mm). Of all stones, 57 (52%) were visible on plain film; 44 (40%) were seen on CT radiographs. The sensitivity of 79 small stones (< 5 mm) on CT scout radiography was 29% and of abdominal radiography 37%. For 32 big stones (> 5 mm), the sensitivity of CT scout radiography was 66% and of abdominal radiography 87.5%.
CONCLUSION: In this study, plain film was more sensitive than CT scout radiography in revealing ureteral calculi. However, the detection of stones 5 mm or larger had a sensitivity of 66% on CT scout radiographs; 77% (44/57) of the stones visible on plain films were also seen on CT scout radiographs. We therefore believe that CT scout radiography can be used as a baseline study in most patients with big ureteral stones.