Acute appendicitis: Comparison of helical CT diagnosis - Focused techniquewith oral contrast material versus nonfocused technique with oral and intravenous contrast material

PURPOSE: To compare the diagnostic accuracy of focused helical computed tom ography (CT) with orally administered contrast material with that of nonfoc used, helical CT with orally and intravenously administered contrast materi al. MATERIALS AND METHODS: After receiving oral contrast material, 228 patients with clinically suspected appendicitis underwent focused appendiceal CT (5 -mm section thickness, 15-cm coverage in the right lower quadrant). Immedia tely thereafter, helical CT of the entire abdomen and pelvis was performed following intravenous administration of contrast material (abdomen, 7-mm se ction thickness; pelvis, 5-mm section thickness). Studies were separated an d independently interpreted by three observers who were blinded to patient names. Diagnoses were established by means of surgical and/or clinical foll ow-up findings. RESULTS: Fifty-one (22.4%) of 228 patients had acute appendicitis. Readers nosed appendicitis with 83.3%, 73.8%, and 71.4% sensitivity and 93.0%, 92.3 %, and 97.9% specificity with focused nonenhanced appendiceal CT. Readers d iagnosed appendicitis with 92.9%, 92.9%, and 88.1% sensitivity and 93.7%, 9 5.1%, and 96.5% specificity with nonfocused enhanced CT. Summary areas unde r the receiver operating characteristic curve estimates for focused nonenha nced and nonfocused enhanced CT were 0.916 and 0.964, respectively; the dif ferences were statistically significant (P < .05) for two of three readers. All readers demonstrated higher sensitivities for detecting the inflamed a ppendix with nonfocused enhanced CT. Appendicitis was missed with focused C T in two patients whose inflamed appendix was not included in the imaging o f the right lower quadrant. All readers, were significantly more confident in diagnosing alternative conditions with nonfocused enhanced CT. CONCLUSION: Diagnostic accuracy of helical CT for acute appendicitis improv ed significantly with use of intravenous contrast material.