UW News

October 9, 2001

Misdiagnosis of appendicitis continues despite new tools

Although more diagnostic tools are available now than ever, there has been no improvement in the rate of misdiagnosis of appendicitis during the last decade, according to University of Washington researchers.

Despite the availability of the new tests, in nearly one of four appendectomies performed in women of childbearing age, the removed appendix is actually not infected. The rate of misdiagnosis among young women and older men has actually increased, according to the results of the study, which are being published in the Oct. 10 issue of the Journal of the American Medical Association.

“For whatever reason, the promise of this new diagnostic technology has not been realized,” says Dr. David Flum, lead author of the study, a surgeon and a Robert Wood Johnson clinical scholar at UW. “We need to conduct more studies to determine what is going on when these new technologies are applied around the country.”

Appendectomy is one of the most frequently performed surgical procedures in the United States. Any given person begins life with a 7 percent chance of appendicitis.

The misdiagnosis rate among men is about 9 percent, versus 23.2 percent among women. The disparity may be because women have more complex anatomy in the right side of their abdomen, such as an ovary, a uterus and fallopian tubes. Inflammation of the appendix is sometimes hard to detect, even for experienced physicians. Because of the appendix’s size, its nickname is the “six centimeter beast of the belly.”

The appendix is a tube connected to the side of the intestine. When its tiny opening is blocked and infection develops, the most common symptoms are pain in the lower right side of the belly, loss of appetite and nausea. However, in many cases the diagnosis is more difficult to establish. When appendicitis is misdiagnosed, the true culprit for the pain varies. In men, the cause may be an inflamed lymph node or a viral infection of the intestinal tract. In women, the problem may be infection of the ovary or uterus, or ectopic pregnancy (when a fertilized ovum implants outside the uterus).

Diagnostic tests developed during the last 12 years include computed tomography (CT), ultrasound, and laparoscopy. These tests are reportedly quite effective in detecting appendicitis. But to measure the impact that the availability of tests has had on misdiagnosis in appendicitis, researchers examined the records for 85,790 appendectomies in Washington state from 1987 to 1998. During this time, the tests were becoming more widely available — and yet, the researchers found that misdiagnosis remained at about 15 percent overall. In fact, the rate of misdiagnosis among women of childbearing age increased 1 percent a year and the rate of misdiagnosis among patients older than 65 increased 8 percent a year.

The CT scan has the highest reported rate of accuracy in diagnosis, but it is not perfect. Because the appendix is small and located near the back of the belly, often behind the colon, it can be hard to see even a normal organ in the CT picture. The appendix is near several other organs that themselves could be inflamed.

It can be hard to diagnose appendicitis at the time of the operation. “When you are suspicious that someone has appendicitis, you don’t want to be wrong and leave the appendix in,” Flum said. “Untreated appendicitis can lead to rupture and even more complications, so many surgeons prefer to take it out even if it looks normal at the time of the operation.”

Patients who have their appendix removed can expect to spend more than three days accruing hospital and medical costs. It has been estimated that 40,000 Americans are misdiagnosed in this way per year, and related hospitalizations cost the nation more than $700 million a year. The cost of misdiagnosis can be more than money. Some patients develop infections of the skin or pelvis, or other complications after surgery.

“There are no small operations. Removal of a normal appendix is not trivial by either cost to society, or cost to the patient individually,” Flum says.

More study is needed, Flum said, to reconcile a seeming paradox. When individual hospitals conduct formal studies of diagnostic tools like CT scans, the rate of misdiagnosis of appendicitis drops dramatically. But the JAMA paper indicates that when looking at the entire state, the availability of these tests has not helped in reducing misdiagnosis.

“It’s very striking to have such a contrast between published reports of how good these tests are, and this new population-based evidence that they are not making a big impact,” Flum says.

Among the possibilities to explain why there has not been improvement over time:

– The tests may not be as effective outside of the places where the studies take place.
– The tests may be good, but not be applied to the right people, or often enough.
– The tests may be good and used properly, but the results are not available quickly enough to affect care. Surgeons often have to act quickly if they think someone has appendicitis.

Other authors of the paper are Dr. E. Patchen Dellinger, UW Department of Surgery in the School of Medicine Dr. Thomas Koepsell of the Departments of Epidemiology and Health Services in the UW School of Public Health and Community Medicine and Dr. Arden Morris of the Robert Wood Johnson Clinical Scholars Program.