Appendectomy? Scan me first, doc.

For emergency room doctors, appendicitis can be a tough call. A missed diagnosis can lead to a burst appendix and complications for the patient. On the other hand, rushing to surgery can mean taking out a perfectly good appendix.

Both occur frequently. Doctors initially fail to diagnose 20 percent of appendicitis cases. As a result, missed appendectomies are the most common successful malpractice claim made against emergency room physicians, studies in the United States and Europe show. What's more, in 15 to 40 percent of appendectomies, doctors end up removing a healthy organ.

In the United States, roughly 250,000 people are treated for appendicitis each year. To improve the odds of getting it right, doctors at Massachusetts General Hospital in Boston took computerized tomography (CT) scans of 100 consecutive patients hospitalized for suspected appendicitis. The doctors had made their preliminary diagnosis on the basis of the patients' medical histories, physical examinations, and laboratory tests.

The CT scans showed that only 53 of the 100 patients indeed had appendicitis. Among the 47 people who proved to have a different ailment, the scans prevented unneeded appendectomies in 13 who had been slated for emergency surgery, the researchers report in the Jan. 15 New England Journal of Medicine.

Overall, the CT scans were accurate in 98 of the 100 cases, says coauthor Patrick M. Rao, an emergency radiologist at the hospital. One CT scan missed a case of appendicitis; another identified a case falsely.

An appendix scan takes 15 minutes to perform. "Fifteen minutes is nothing in the big scheme of things," Rao says, noting that many potential appendectomy patients wait for hours in emergency rooms. Rao and his colleagues calculated the cost differential between removing a healthy appendix and having a CT scan at 16 to 1. The hospital thus saved roughly $44,700 overall for the 100 patients.