The pre-operative use of computed tomography (CT) to make a definitive diagnosis in cases suggestive of acute appendicitis is linked to a poorer patient outcome than a straight-to-surgery approach.

In their study, the investigators also observed that diagnostic CT delayed surgery and increased the risk of perforation.

"There has been a somewhat reflexive use of CT since it has become widely available," Dr. Herbert Chen of the University of Wisconsin at Madison told attendees of Digestive Disease Week 2007, which is underway here.

Dr. Chen and colleagues reviewed the records of 410 adult patients who underwent appendectomy at their institution over a three-year period. Of these, 62 per cent had pre-operative diagnostic CT, while 38 per cent proceeded straight to the operating room.

Pre-operative white cell counts were similar in the two groups. However, time to surgery was a mean of three hours longer in those who underwent pre-operative CT. Patients who did not have a CT were in surgery within a mean of five hours, but for those who had a CT, surgery was not performed for more than eight hours.

The perforation rate was 17 per cent in the patients who had a CT scan before surgery compared with eight per cent in those who did not. The significantly longer time to intervention with the diagnostic procedure may also account for the more than two-fold increase in complications.

Even with rapid intervention, there is a "significant complication rate" with acute appendicitis, Dr. Chen pointed out.

Pre-operative CT is not necessary in cases with straightforward signs and symptoms of appendicitis, the investigator advised.

"If, after a thorough physical examination, the diagnosis is still in question, then patients should be scanned." These patients tend to be older, female and have symptoms that are atypical for acute appendicitis.

"The CT should theoretically be relatively quick," Dr. Chen told Reuters Health. "But if contrast is used, then that takes time to swallow and be absorbed. Contrast is typically used, because physicians want to maximize the information obtained with exposure to radiation.

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