It took 2,000 years to evolve, but in the short time since the end of World War II, one of the oldest operations in medicine has diminished to near-extinction. Some physicians ignore its demise, but others say the operation -- the post-mortem examination or autopsy -- must be rescued from oblivion to secure the future of medicine.

An autopsy is a two- to four-hour surgical procedure in which a pathologist opens a body and examines internal organs to determine the cause of death. Thirty years ago, such examinations were performed in nearly half of all deaths in the United States each year. Today, that figure has dropped to less than 15 percent. In a many hospitals, it hovers between zero and 5 percent.

Advocates of the autopsy say the procedure is still "the ultimate audit" of medical care, a valuable tool for illuminating diagnostic error and supplying new information about disease, not to mention teaching medical students about anatomy. Skeptics say it is often useless.

The reasons for the autopsy's demise remain cloudy, and theories seem as abundant as theorists. Among the factors that may have contributed to the trend are: Better medical technology. Many observers believe advanced diagnostic tools, such as computerized tomography (CT) scans, studies using radioactive materials and ultrasound studies permit better diagnosis of disease and often preclude the need for autopsy.

But this has not been shown to be the case, says Dr. Lee Goldman, a Boston internist. In a 1983 study on the value of the autopsy, Goldman's research group concluded that advances in diagnostic technology have not made the autopsy obsolete. Despite new technology, the study found, about 10 percent of autopsies disclose information that "if known before death, might have led to a change in therapy and prolonged survival." Apathy among pathologists. With the rise in "high tech" medical equipment has come a greater stratification in the roles of physicians who do autopsies, says Dr. Marie Valdes-Dapena, professor of pathology and pediatrics at the University of Miami School of Medicine. Increasingly, she says, the more experienced and highly paid the pathologist, the less often he or she does autopsies.

Contrary to practice 20 to 30 years ago, the autopsy is now relegated to the most junior staff. Nearly every senior pathologist, she says, "would rather not stand up for an hour and do that messy, smelly job when he could sit in the quiet of his office or peer into the electron microscope." Because the least experienced pathologists wind up doing the autopsies, other physicians may have less confidence in the results. Economic disincentives. Most pathologists are not paid per autopsy, but receive a salary that is fixed, regardless of the number of autopsies they perform. Hospitals, furthermore, often don't encourage the procedure since they must absorb the cost directly -- at least $1,000 per autopsy. Absence of autopsy quotas. From 1957 to 1970, the Joint Commission on the Accreditation of Hospitals (JCAH) recommended -- at first informally, then formally -- that hospitals perform autopsies in 20 to 25 percent of deaths. It rescinded the quota because many hospitals could not reach the minimum and because "a number of new diagnostic tests has made autopsy less important than it had been in the past," says Dr. James Roberts, commission vice president for accreditation.

Additionally, many hospitals were performing unnecessary autopsies simply to satisfy the recommendation, says Jan Shulman, the commission's manager of extended programs. In place of the quota, the commission now suggests that hospitals do autopsies when they deem necessary. Apathy of other physicians. There are many explanations for physicians' diminished interest in autopsy. Some blame it on "information overload," others on the unprecedented demands on a doctor's time. According to Goldman, however, "the principal, though often unspoken, reason is that physicians feel the autopsy isn't worth the time and effort because it seems to make no difference in patient care in the tangible future."

Goldman and other physicians who have examined the question also surmise that physicians may shy away from autopsy because they fear malpractice suits if autopsy findings contradict the diagnosis before death. "There was a time when people didn't think about suing their doctors," Goldman says.

Concern over the dying autopsy has escalated in the past year or two. In July the College of American Pathologists convened to debate why the autopsy rate is declining and what ought to be done about it. Currently, the JCAH, partly because of pressure from pathologists groups, is reviewing its recommendations on autopsy.

The January issue of the American Journal of Medicine carried a report concluding that the benefits of autopsy far outweight the drawbacks.

On Feb. 1, a National Academy of Sciences ad hoc committee on autopsy policy found that a national autopsy policy is "a matter of concern" and deserves further investigation, according to Barbara Filner, director of the NAS Institute of Medicine health science policy division.

Those who call for increasing the number of post-mortems say more of the operations are needed because: Autopsy exposes error and therefore discourages the physician from burying his mistakes. Autopsy is vital to research and national health statistics. Discovery of the mechanisms leading to acquired immune deficiency syndrome (AIDS) was made possible by autopsy studies. Physicians made the link between cigarette smoking and cancer because they noticed lung damage in smokers autopsied for other reasons. It comforts the family of the deceased by offering the definitive cause of death and relieving feelings of guilt. It helps detect hereditary illness. Valdes-Dapena was able to predict and help a patient manage her kidney disease because autopsies on her father and grandmother revealed a hereditary kidney disease. Autopsy is essential in medical education. The declining number of autopsies, says Roberts, "has or will result in a less than sufficient training for pathologists."

Mounting interest in revitalizing the autopsy seems to parallel growing evidence that autopsies still turn up a significant number of diagnostic surprises. This may be due, in part, to the complexity of disease. In 1980, a large percentage of missed diagnoses were of diseases that few people died from in 1970, says Goldman. This means that as people live longer, they tend to die from more complex and difficult-to-diagnose diseases.

Those who question the value of autopsies are generally less vocal, and often in less senior positions, than supporters of the procedure. Few physicians frankly oppose autopsy, but some skeptics suggest that those who would increase the numbers of post-mortems have a professional stake in the matter.

"For many pathologists who stress the importance of autopsy, I think, this represents to some degree a promotion of self-interest," says Dr. Stanley Burrows, clinical professor of pathology at Temple University School of Medicine in Philadelphia.

Burrows believes the issue may have polarized academic and nonacademic pathologists. The academics, he says, seem to favor more autopsies, which would increase "the need for more pathologists, more trainees, and would justify better income for pathologists." The nonacademics, he says, favor deemphasizing the procedure because they perceive it as a waste of time and money.

Burrows conducted a study on autopsies in 1973 that found that fewer than 5 percent of the postmortems he reviewed detected significant errors in diagnosis. He now favors neither increasing nor decreasing the number of autopsies, but calls instead for better selection of autopsy subjects, in order to make the procedure more productive.

While the debate continues, the autopsy seems to edge closer to extinction. Its decline shows no obvious signs of turning around, and no savior has emerged.

The commission on hospital accreditation probably won't restore its percentage quota because "it's very difficult to be that specific," says Dr. David Lowell, clinical professor of pathology at Yale University School of Medicine, who favors increasing the number of autopsies performed. "You can't set a percent that applies to a hospital with 50 beds that also applies to a university medical center with 500 beds."

The best ways to renew pathologists' interest in autopsy, Lowell said, are to reeducate them on its value and to encourage "adequate compensation" from third-party payers, which seems nearly impossible.

"Right now insurance companies like to pay only for the living," Lowell said. "It would take a much greater degree of foresight on their part to recognize that a higher autopsy rate is a reflection of a higher quality of medical care and probably a better value for the buck."

"The whole procedure of increasing the autopsy rate," said Goldman, "is very slow. It's one of those ill-defined processes of consciousness-raising."