Jo-Anne Coe took every medical test recommended by doctors and was determined to stay healthy. At 69 years old, she was working as an aide to former Sen. Bob Dole while remodeling a Virginia farmhouse.

But on Sept. 27, while shopping for kitchen cabinets, Ms. Coe felt an intense pain in her back and went to an emergency room. Unlike chest pain, back pain often isn't regarded as urgent, so she waited 90 minutes to see a doctor. After finding that blood was pouring into her body from a leaking aneurysm -- a ballooned section of a blood vessel -- alarmed doctors rushed her into surgery. During the operation, on her torn aorta, she died.

The popular impression is that aneurysms are like lightning: striking rarely, suddenly and unpredictably. In fact, the most lethal aneurysms, those on the aorta, develop slowly, are often easy to diagnose with an inexpensive ultrasound test, and can usually be treated.

But most are never diagnosed, with the result that bursting aneurysms in the abdomen and chest kill an estimated 18,000 Americans a year -- more than AIDS or brain cancer, and four times as many as cervical cancer. Based partly on estimates from doctors, deaths from all types of aneurysms, including cerebral, equal prostate cancer's toll and approach that of breast cancer.

Neglected Disease

For all this, there is no national effort to find aneurysms before they rupture. Doctors almost never inquire about a family history of aneurysms, even though they have a strong familial link. They draw minuscule research funding. And while vast medical industries have grown up to detect ills such as prostate cancer and diabetes -- with doctors routinely ordering tests and insurers routinely paying -- doctors hardly ever suggest that a well patient take a simple test that could detect countless repairable aortic aneurysms. It costs as little as $40 at some centers.

"These deaths are basically preventable if people just got themselves screened," says M. David Tilson, who has treated and researched aneurysms for more than a quarter-century and now holds an endowed chair in surgery at Columbia University. "Aneurysm disease is one of the most neglected diseases in American history."

Why this anomaly? An important reason is that aneurysms produce no large group of patients motivated to raise awareness and funding. Most people with an aneurysm never have symptoms and don't know about it. If it bursts, they're usually dead or disabled. In a third scenario, where the aneurysm is found and surgically repaired, patients aren't likely to become activists. Most are essentially cured, unlike the many people who live for years fighting cancer, AIDS or heart disease.

A rare exception is Bill Maples, who launched a support group and Web site out of his home after having an aneurysm found and fixed. "We have no funding whatsoever," says Dr. Maples, a retired college biology professor in Carrollton, Ga.

A different obstacle prevents screening tests from becoming common and covered by insurance. Many insurers take their cue from Medicare, which doesn't cover aneurysm screening. Now, however, a debate is stirring in medicine over whether some groups of people with no symptoms should be screened for aneurysms.

K. Craig Kent, chief of vascular surgery at New York Presbyterian Hospital-Cornell, did an economic analysis concluding that ultrasound screening for abdominal aneurysms would be more economical, in terms of life-years saved, than mammography. In an article last August in the journal Surgery, Dr. Kent recommended that all men over 60 be offered a quick ultrasound exam of the stomach. He also urges the test for all women over 60 who have a family history of aneurysms.

'Social Dilemma'

What such a policy might add to the country's surging medical bill is unknown. The cost would include not only the screening but also monitoring of aneurysms found, and surgery for some of them. To Rodney White, a surgery professor at UCLA, "It's a social dilemma because you can't afford to screen everybody. But the argument for screening is stronger now [and] a lot of professional groups are advocates for screening."

Aneurysms arise when a thinning, weakening section of an artery wall balloons out. Such spots are considered aneurysms when they reach twice the artery's normal diameter. The deadliest occur in the aorta, the big vessel stretching from the heart to the abdomen.

They usually produce no symptoms. The majority never burst. But when they do, the patient dies about 90% of the time, often never reaching a hospital. By contrast, when a large aortic aneurysm is found and operated on, the survival rate is typically 95% or better, depending on the hospital and where on the aorta the aneurysm is.

Most deaths from aortic aneurysms involve the abdomen, where they can be detected by the inexpensive, and very accurate, ultrasound test. The rest of aortic-aneurysm deaths -- an estimated 2,500 a year in the U.S. -- occur where the vessel runs through the chest. Spotting these usually requires a CT scan, which can cost as much as $800.

Cerebral aneurysms present a more complicated case, because detecting them costs more and it's not so clear which ones need surgery. But these, too, can be deadly. They kill roughly 14,000 Americans a year, estimates Gary Steinberg, chief of neurosurgery at Stanford University Medical Center.

The aneurysm toll actually may be much higher. In the absence of autopsies, coroners tend to attribute sudden deaths to cardiac failure. Each year in the U.S., about 450,000 sudden deaths, most of them unautopsied, are ascribed to cardiac events. Dr. Kent says it's likely a substantial portion actually are due to burst aortic aneurysms.

High blood pressure raises the risk, both that an aneurysm will develop and that it will someday burst. Yet while doctors routinely check blood pressure, and warn about heart risk, they rarely mention aneurysms.

Meanwhile, doctors and fitness experts are increasingly preaching the benefits of weightlifting, including for the elderly. But "heavy weightlifting and heavy straining could worsen aneurysms," says Christopher K. Zarins, chief of vascular surgery at Stanford University Medical Center. He suggests that people with aneurysms use only light weights.

The National Institutes of Health will spend $2.77 billion for research on AIDS this year, along with $732 million on breast cancer and $408.3 million on prostate cancer. The amount for abdominal aneurysms is just over $6 million.

Some doctors say cerebral aneurysms, in particular, warrant more study. It is difficult to know which ones are likely to burst, and it takes a $1,500 magnetic-resonance or CT scan to find them. Despite the uncertainty, experts recommend the exams in a number of cases, such as persistent severe headaches and vision problems.

Devastated

Lois Porteous might have benefited. Suffering from severe headaches and a loss of peripheral vision on one side, she was given headache medicine but no scan. Last Jan. 30, the 58-year-old in Zebulon, N.C., collapsed in her kitchen after an aneurysm behind her eye burst. She survived but needs 24-hour care. "It just devastated her," says a son, Michael.

Screening for aneurysms on the aorta would be simpler, because these appear in more-distinct patterns. For instance, 80% occur in men, and the odds rise with hypertension, smoking and arteriosclerosis.

In addition, when this type of aneurysm is spotted, it's easier to know if surgery is needed, because the risk of rupture increases with size. Normal aortas range between 1.6 and 2.8 centimeters wide. Doctors say any sections wider than four centimeters generally need to be watched closely. Many are stable, but when they start growing, alarms go off. If a spot gets as wide as 5.5 centimeters, the risk of rupture may be high enough to call for surgery. The death rate in surgery isn't negligible but is much lower than that from burst aneurysms.

U.S. surgeons repair about 50,000 abdominal aneurysms each year, typically replacing the puffed-out area with a plastic or fabric tube. Some now use a less-invasive procedure that threads a tubular device called a stent-graft into the bubble.

Over two decades, the number of intact aortic aneurysms diagnosed in the U.S. has tripled to about 200,000 a year. The surge appears partly to reflect the greatly increased use of CTs, MRIs and the like, to check for tumors or other conditions. Relatively few scans are done simply to hunt for aneurysms.

Would insurers pay if tests to detect aneurysms were done to screen symptomless patients, rather than to diagnose symptoms in individual cases? So far, insurers haven't faced the issue. When asked, some point to the added costs that would result from monitoring and surgery, and say they haven't been convinced that screening would be broadly effective.

Some doctors also are reluctant to endorse widespread testing. Robert Zwolak, a vascular surgeon at Dartmouth Medical School, says, "We think we can identify a risk group for whom aortic aneurysm screening is appropriate, but we need more substantiation."

A huge British study provided some last fall. After following 61,000 men aged 65 to 74 for an average of four years, it found a 42% drop in risk of death from abdominal aortic aneurysm among those who had been screened. Their aneurysm death risk was 1.9 per 1,000, vs. 3.3 in the others. "Screening can significantly reduce mortality rates associated with abdominal aortic aneurysms," concluded the study, published Nov. 17 in The Lancet, the British medical journal.

A large new study is being organized in the U.S. by the medical schools of Dartmouth, the University of Pennsylvania and the University of Pittsburgh. Initially it will measure the prevalence of aneurysms; a later phase will check for a mortality benefit from screening.

"There is reasonable emerging evidence suggesting that it's reasonable to screen men over 60" for abdominal aortic aneurysm, "particularly if they have a history of smoking, and anyone with a first-degree relative with an aneurysm," says Jack L. Cronenwett, a study organizer and chief of vascular surgery at Dartmouth. That would have included Ms. Coe in Virginia: Her mother, too, had an aortic aneurysm.