A study of more than 63,000 appendectomies done in Washington hospitals between 1987 and 1998 finds that the rate of misdiagnosis remained constant, says a report in the Oct. 10 issue of the Journal of the American Medical Association, which states that in one of every six of those operations, the appendix that was removed was normal.
"Contrary to expectations, the frequency of misdiagnosis leading to unnecessary appendectomy has not changed with the introduction of computerized tomography, ultrasonography and laparoscopy," the journal report says.
"It's striking to have such a contrast between published reports of how good these tests are and this population-based evidence that they are not making a big impact," says Dr. David R. Flum, a Robert Wood Johnson clinical fellow at the university and lead author of the study.
The appendix is a wormlike tube, about 3.5 inches long in adults, that branches from the large intestine. It can become infected and inflamed when its opening is blocked. Without treatment, the appendix can rupture, causing a life-threatening infection of the abdominal cavity.
Appendectomy is one of the most common operations in the United States; the lifetime chance of having that surgery is 7 percent. Computerized tomography and ultrasonography, which give detailed images of the intestine, and laparoscopy, which allows a physician to look inside the abdominal cavity, are intended to prevent unnecessary appendectomies.
Nevertheless, the Washington study found that the rate of misdiagnosis remained constant over the study period, even as the new technologies became widely available. The overall rate of misdiagnosis was 15.5 percent. It was much higher in women (23.2 percent) than in men (9 percent), because the female anatomy of the right side of the abdomen is complex.
The rate of false diagnosis actually increased for some patients over the period of the study -- 1 percent a year for women, 8 percent a year for people over 65, the report says.
Flum notes an apparent paradox in the finding. Controlled tests of new techniques such as computerized tomography in individual hospitals have found a reduced rate of misdiagnosis. One possibility is that the technology is not being used as effectively in community hospitals as in the research hospitals where such studies are done, he says.
"It could be that what we observe is a difference in hospitals," says Dr. James M. Wagner, associate professor of internal medicine at the University of Texas Southwest Medical Center in Dallas, who did a report on the diagnosis of appendicitis in the same journal five years ago. "The positive findings were in research hospitals, and one way to explain the disparity is that this study looked at a different group of hospitals."
It's also possible that the finding is not as dire as it sounds, Wagner says. "When a surgeon does a laparoscopy, you look at the appendix," he says. "How good are surgeons at deciding whether an appendix is inflamed? If it is equivocal, you may take it out to be on the safe side. It's been recommended in the medical literature that because surgeons do not have real good accuracy at determining inflammation, they should take the appendix out regardless of whether it may turn out to be normal."
Wagner adds that the report raises a negative implication "that the new technology is no help and has not furthered the treatment of patients. I am a bit skeptical about that."
What To Do
The symptoms of appendicitis -- discomfort around the navel developing into sharp pain in the lower right of the abdomen, accompanied by fever, nausea, or vomiting -- can signal a number of other abdominal conditions and require an immediate call for medical help.
Information about appendicitis is available from the National Institute of Diabetes and Digestive and Kidney Diseases and MedicineNet.