INTEROBSERVER VARIABILITY IN THE INTERPRETATION OF UNENHANCED HELICALCT FOR THE DIAGNOSIS OF URETERAL STONE DISEASE

Purpose: The purpose of this study was to analyze interobserver agreem ent in the interpretation of unenhanced helical CT (UHCT) for the eval uation of ureteral stone disease and obstruction. Method: One hundred three UHCT examinations were independently and retrospectively reviewe d by five readers including attending radiologists, a radiology reside nt, and an attending urologist. Examinations were interpreted as posit ive, negative, or indeterminate for ureteral stone disease and obstruc tion, The Cohen kappa test was used to measure interobserver agreement . The accuracy of the readers was also assessed. Results: The kappa va lue ranged from 0.67 to 0.71 among the three attending radiologists an d from 0.65 to 0.67 among the radiology attending physicians and radio logy resident. Although the urologist tended to agree less well with t he other readers (kappa range: 0.33-0.46), there was no statistically significant difference (p < 0.05) in the accuracy among all five reade rs. The percentage of cases interpreted as indeterminate ranged from 8 to 25% and almost invariably involved difficulty distinguishing phleb oliths from minimally obstructing distal ureteral calculi. The percent age of UHCT scans correctly interpreted as positive and correctly inte rpreted as negative ranged from 73% (n = 27) to 86% (n = 32) and 63% ( n = 22) to 86% (n = 30), respectively. Conclusion: Interobserver agree ment was very good among the radiology attending physicians and reside nt and moderate with the urologist. The examination is an accurate tec hnique in the evaluation of ureteral stone disease, although limitatio ns exist, particularly in the diagnosis of minimally obstructing dista l ureteral calculi.