Computed tomography and ultrasonography in the diagnosis of appendicitis -When are they indicated?

Hypothesis: Relative merits and indications exist for ultrasonography (US) and computed tomography (CT) in the diagnosis of appendicitis. Design: Prospective study. Setting: General community and tertiary care hospital. Methods: Ninety-nine patients (50 males and 49 females) were studied. Follo wing consent, the initial disposition was recorded, designating the patient for operation, observation, or discharge from the hospital. Each patient w as studied by CT and US. Studies were independently evaluated by 2 radiolog ists, and the results were designated as positive, negative, or equivocal. The surgeon reevaluated patients before and after learning the results of U S and CT, recording whether the CT scan, US,, or reexamination influenced t he final disposition. Results: Fifty patients had appendicitis; 6 appendixes were perforated. The initial clinical impression called for 44 operations, 49 observations, and 6 discharges. Thirty four patients had their treatment plan changed from t he initial disposition. Ultrasonography did not affect the initial impressi on. In contrast, 18 patients were rediagnosed solely on CT scan findings. S even patients were rediagnosed by reexamination. Of 44 patients initially d esignated for operation, the CT scan and reexamination spared 6 females fro m surgery; the negative appendectomy rate potentially decreased from 50% to 17% (P=.03). The CT scan, US, or reexamination failed to spare 2 males fro m exploration with negative results. Of the 49 patients initially designate d for observation, 23 were rediagnosed after reevaluation, 13 were discharg ed from the hospital, and 10 underwent expedient operation. One patient was spared from inappropriate discharge from the hospital. The reliability of the CT scan was good, with high sensitivities and specificities. Equivocal scan re suits lowered the diagnostic value. Conclusions: Selective use of a CT scan with a second examination can impro ve the diagnostic accuracy and management of suspected cases of appendiciti s by (a) reducing the negative appendectomy rate in females, (b) moving pat ients from observation to earlier operation or discharge from the hospital, and (c) preventing inappropriate discharge of patients with appendicitis.