UNENHANCED HELICAL CT FOR SUSPECTED ACUTE APPENDICITIS

OBJECTIVE. The purpose of this study was to determine the diagnostic a ccuracy of unenhanced helical CT scans in patients with a suspected ac ute appendicitis. SUBJECTS AND METHODS, Over a 20-month period, 109 ad ult patients with suspected acute appendicitis were referred by the em ergency department for an unenhanced helical CT scan. Each scan was ob tained in a single breath-hold from the T12 vertebral body to the pubi c symphysis using a 5-mm collimation and a pitch of 1.6. No patients w ere given oral or TV contrast media. The primary CT criteria for diagn osing acute appendicitis was the identification of an appendix with a transverse diameter larger than 6 mm with associated periappendiceal i nflammatory changes. The presence of an appendicolith was considered a secondary finding as was isolated periappendiceal inflammation; howev er, appendicitis was not diagnosed in such patients unless an enlarged appendix was definitely identified, Final diagnoses were established by surgical or clinical follow-up and were compared with the original CT reports. RESULTS. We found 66 true-negatives, 37 true-positives, fo ur false-negatives, and two false-positives that yielded a sensitivity of 90%, a specificity of 97%, a positive predictive value of 95%, a n egative predictive Value of 95%, and an accuracy of 94%. An alternativ e diagnosis was established by an unenhanced helical CT scan in 24 pat ients (22%), which included cecal diverticulitis (seven patients), uri nary tract disease (five patients), adnexal pathology (four patients), sigmoid diverticulitis (two patients), small bowel disease (three pat ients), right lower quadrant tumor (two patients), and an infected dia lysis catheter (one patient). CONCLUSION. Unenhanced thin-section heli cal CT is an accurate, effective technique for diagnosing acute append icitis.