• Scott Van Appledorn, Adam J Ball, Vipul R Patel, Sandy Kim, and Raymond J Leveillee.
• Department of Urology, University of Miami School of Medicine, Miami, FL 33136, USA.
• J. Endourol. 2003 Dec 1; 17 (10): 851-4; discussion 854.

Background And PurposePatients with renal colic are frequently evaluated in the emergency room with a helical noncontrast CT scan (NCCT) as the primary imaging modality. Treatment decisions are often based on the size of the ureteral stone(s). We wished to assess the accuracy of NCCT in estimating ureteral stone size compared with plain abdominal (KUB) films.Patients And MethodsForty-eight patients were identified who had ureteral stones seen on NCCT and KUB films performed on the same day. The number of consecutive images on which a ureteral stone was visible on NCCT was multiplied by the reconstruction interval of 5 mm to create a size estimate, which was compared with the measurements of the same stone seen on the KUB film.ResultsThe NCCT overestimated stone size by approximately 30% to 50% compared with KUB.ConclusionCounting the number of consecutive NCCT images depicting a ureteral stone is not an accurate method of stone measurement when a reconstruction interval of 5 mm is used. Urologists should consider stone measurement techniques carefully and understand the limitations of imaging studies when evaluating patients with symptomatic ureteral stones.

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