Can computed tomography scan be performed effectively in the diagnosis of acute appendicitis without the added morbidity of rectal contrast?

The highest degrees of accuracy have been demonstrated for CT scans using rectal contrast in diagnosing appendicitis. However, the administration of rectal contrast is associated with patient discomfort and rarely, rectosigmoid perforation (0.04%). Additionally, the commonly accepted negative appendectomy rate is around 16 per cent. We performed a retrospective review of radiology, operative, and pathology reports of consecutive patients undergoing appendectomy or CT examination for appendicitis during 2006. CT scans were performed without rectal contrast. The accuracy of each type of inpatient CT examination and negative appendectomy rates were determined. Two hundred and thirty-eight patients underwent appendectomy. One hundred and thirty-four appendectomy patients (56%) received a preoperative CT scan. The negative appendectomy rates were 6.3 per cent overall, 8.7 per cent without CT examination and 4.5 per cent with CT (P = 0.3). Two hundred and forty-five inpatient CT scans were performed for suspected appendicitis with a sensitivity of 90 per cent, specificity of 98 per cent, accuracy of 94 per cent, positive predictive value of 98 per cent, and negative predictive value of 91 per cent. CT scanning without rectal contrast is effective for the diagnosis of acute appendicitis making rectal contrast, with its attendant morbidity, unnecessary. The previously acceptable published negative appendectomy rate is higher than that found in current surgical practice likely due to preoperative CT scanning.