AJR:173, December 1999 1447 Trends in the Use of Unenhanced Helical CT for Acute Urinary Colic Michael V. M. Chen1 Ronald J. Zagoria H. Stuart Saunders Raymond B. Dyer OBJECTIVE. Unenhanced helical CT for urolithiasis detection is a limited CT examina- tion that was designed specifically for the detection of urolithiasis. The purpose of this study was to repeat a prior study to assess whether clinicians had broadened the indications and changed the yield and findings of unenhanced helical CT. MATERIALS AND METHODS. One hundred consecutive patients with suspected re- nal colic or flank pain referred for unenhanced helical CT were selected for this study. We re- viewed the original radiographic reports for each patient and recorded the presence of ureteral calculi. Other urinary abnormalities and extraurinary lesions were also recorded and com- pared with the results of the previous study. RESULTS. In this study, 56% of the patients who underwent unenhanced helical CT had symptoms of urinary colic, and 44% of patients had unspecified flank pain, compared with 100% of patients with symptoms of urinary colic 1 year earlier. The sensitivity and specificity of unenhanced helical CT in detecting ureteral calculi were 96% and 99%, respectively. Ureteral calculi were identified in only 28% of the patients versus 49% of patients (p < .01) 1 year earlier. Extraurinary lesions were identified in 45% of the patients versus 16% (p < .01) 1 year before. CONCLUSION. As clinicians developed familiarity with this technique, the indications for performance of unenhanced helical CT were expanded with a consequent reduction in the rate of detection of stone disease and identification of an increased number of extraurinary le- sions, which suggests a demand for emergency abdominal CT studies. Received January 4, 1999; accepted after revision June 2, 1999. ‘All authors: Department of Radiology, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157-1088. Address correspondence to M. V. M. Chen. AJR1999;173:1447-1450 0361-803X/99/1736-1447 © American Roentgen Ray Society I n 1995, Smith et al. [ 1 ] introduced unenhanced helical CT as an mi- tial imaging technique for patients with acute flank pain who would otherwise be referred for excretory urography. Unen- hanced helical CT for urolithiasis was specif- ically designed to detect urinary tract stones. It is not a complete or standard abdominal or pelvic CT examination. The area of examina- tion extends from just above the kidneys through the bladder base. Because it is a lim- ited examination, a reduced charge compara- ble with that for excretory urography may be assigned to unenhanced helical CT. Unen- hanced helical CT has become the preferred technique for examining patients with acute urinary colic [2-9]. Before we advocated conversion from excretory urography to Un- enhanced helical CT, we assessed the value of unenhanced helical CT in a study of 100 con- secutive patients with urinary colic [2]. In that population, 49 patients had ureteral cal- culi, 17 had renal calculi, 16 had extraurinary lesions, and 18 were healthy. As we became more familiar with the technique, it became obvious that the indications for perfor- mance of unenhanced helical CT had been expanded beyond the specific evaluation of urinary colic. The rate of stone detection has decreased, and the number of extrauri- nary lesions that were discovered has in- creased. This realization led to a second study of another 100 patients undergoing unenhanced helical CT, approximately 1 year after the introduction of this technique into our institution, to search for trends in indications and results of unenhanced heli- cal CT in the evaluation of urinary colic and extraurinary diseases. Materials and Methods From January through April 1998, 100 consecu- tive patients (56 males, 44 females) examined in our emergency department and referred for unenhanced helical CI’ were selected for this study. Their aver- age age was 51 years (range, 14-89 years). Of the