Focused helical CT using rectal contrast material only as the preferred technique for the diagnosis of suspected acute appendicitis: a prospective, randomized, controlled study comparing three different techniques.

PURPOSE: Focused helical CT using rectal contrast material only has emerged recently as an accurate diagnostic tool for the evaluation of suspected acute appendicitis. This study was designed to prospectively compare the efficacy of rectal contrast CT to other commonly used contrast-enhanced and nonenhanced CT techniques for the detection of acute appendicitis.

METHODS: A total of 232 patients with clinically suspected appendicitis were randomly assigned to one of three focused helical CT techniques: noncontrast enhanced CT, CT using rectal contrast material only, and dual-contrast CT using both oral and intravenous material. All scans were interpreted by the on-call residents and reported immediately to the surgeon. The sensitivity, specificity, predictive values, and overall accuracy rates were compared between the protocols.

RESULTS: One hundred eleven patients (48 percent) had acute appendicitis. The sensitivity and specificity rates of rectal contrast CT were 93 and 95 percent, respectively, with overall accuracy of 94 percent. The sensitivity and specificity rates of dual-contrast CT were 100 and 89 percent, respectively, with overall accuracy of 94 percent. The sensitivity and specificity of noncontrast enhanced CT were 90 and 86 percent, respectively, but the overall accuracy was significantly lower (70 percent) compared with the other studies.

CONCLUSIONS: Rectal contrast CT is as accurate, although less sensitive, compared with dual-contrast CT and significantly superior to noncontrast-enhanced CT for the diagnosis of acute appendicitis. Rectal contrast CT may be performed rapidly, saves resources, and may avoid the diagnostic delay and potential allergic reactions associated with oral and intravenous-enhanced studies, and, therefore, may be the preferred initial technique in the diagnostic workup of suspected acute appendicitis.