[Unenhanced spiral CT in the diagnosis of acute appendicitis].

PURPOSE: To evaluate the role of unenhanced spiral computed tomography (CT) in the work-up of patients with suspicious symptoms of acute appendicitis.

MATERIALS AND METHODS: Sixty-five patients with suspected acute appendicitis (34 (52%) women and 31 (48%) men), were studied with spiral CT without administration of IV or oral contrast. From the upper L1 vertebral plate to the superior border of the iliac wings, slices of 10 mm collimation with 8 mm/sec table speed were taken, and from that level to the acetabular roof level, 5 mm thick slices were obtained with a table speed of 5 mm/sec and tube rotation time of 1.5 sec. The diagnosis of acute appendicitis was made by seeing a dilated appendix vermiformis greater than 6 mm in diameter and/or an appendicolith accompanied by periappendiceal inflammatory changes. The findings were compared with surgical and pathological results. Those patients who were not operated on were followed-up for 3 months.

RESULTS: Acute appendicitis was diagnosed in 28 (43%) of the 65 patients. Of the 28 patients with a CT diagnosis of acute appendicitis, 25 (38%) had acute appendicitis proven by surgery and pathology. Twenty-one (32%) patients had a normal CT study and 16 (25%) patients had non-appendiceal pathologies. There were 25 true-positives, 35 true negatives, 3 false positives and 2 false negatives. Non-contrast helical CT had a sensitivity of 93%, specificity of 92%, accuracy of 95%, positive predictive value of 89% and negative predictive value of 95% in the diagnosis of acute appendicitis.

CONCLUSION: Non-contrast CT is an accurate, reliable and efficacious method in the diagnosis of acute appendicitis. It also has the advantage of showing other pathologies mimicking the symptoms of acute appendicitis.