A prospective trial of computed tomography and ultrasonography for diagnosing appendicitis in the atypical patient.

BACKGROUND: The surgical diagnosis of acute appendicitis is customarily made on clinical grounds alone using history, physical examination, and white blood cell count. In the atypical patient, ie, the patient with prolonged symptoms, inconsistent history, or misleading physical examination, diagnostic studies should be helpful in establishing the appropriate diagnosis. Computed tomography (CT) scan and ultrasonography (US) have demonstrated utility in diagnosing appendicitis but have not been studied in the atypical patient population.

METHODS: A retrospective review of 500 consecutive appendectomy patients, coupled with a review of the literature, resulted in the development of an algorithm to help the medical physician to differentiate the atypical patient requiring an imaging study from those requiring immediate surgical consultation. This patient population was entered into a prospective, randomized study of CT scan or US examination.

RESULTS: Between May 1997 and May 1999, 106 patients were enrolled in the study; 17 were later excluded from the study because of typical presentation and direct admission to surgery without diagnostic imaging. Forty-nine patients were randomly assigned to CT scan and 40 to US examination. CT scan was 100% specific and 97% sensitive (P = 0.018). US was 90% specific and 76% sensitive. Based on the results of these imaging studies, 70 of the study patients underwent exploration for suspected appendicitis or other acute inflammatory process.

CONCLUSION: A subset of patients presenting with possible acute appendicitis has been identified that should benefit from imaging of the appendix prior to surgical consultation. For this group, CT scan appears superior to abdominal and pelvic US in terms of diagnostic accuracy and reliability. With this approach, a low incidence of negative laparotomies was achieved.