For years, the painful condition of interstitial cystitis was considered extremely rare, impossible to treat and probably psychological in origin.

It remains virtually impossible to treat -- although there are a variety of therapies, some of which help some of the patients some of the time. But doctors have learned a great deal more recently about this bladder disorder, finding that it is more common than previously thought, more debilitating, and not a figment of the imaginations of its 200,000 to perhaps as many as 500,000 victims. For many women, it makes holding a job impossible.

Symptoms include frequent urination and severe abdominal pain; the cause remains unknown, although women with the disease have tiny pinpoint hemorrhages in the bladder.

The new findings were brought to light in a report presented at a two-day workshop last week conducted by the National Institute of Diabetes and Digestive and Kidney Diseases (NIADDK) of the National Institutes of Health.

The fact of the workshop was almost as remarkable as the report itself, says Dr. Vicki Ratner. Ratner, a resident in orthopedic surgery at Montefiore Hospital in the Bronx, has a deeply personal interest in interstitial cystitis, or IC. She has it. In fact, hers may be one of the most celebrated bladder conditions in medical history.

As one of the founders of the Interstitial Cystitis Association (ICA), a self-help, lobbying and research organization for women (and the few men) with the disorder, Ratner tells her own story whenever she can find someone to listen. And, in the three years since 10 urologists told her she'd just have to live with the pain, she has found that whenever she tells her story -- on TV or at meetings or in newspaper interviews -- there are responses from literally thousands of women with the same problem, with the same non-answers from doctors, with the same anguish.

That IC causes anguish in its sufferers was something Ratner and many others already knew. Ratner likens the pain to an abscessed tooth. ("Imagine trying to operate on somebody when you've got an abscessed tooth," she says.) The epidemiological study, conducted by the Urban Institute with two University of Pennsylvania urologists, surveyed a randomly selected group of urologists and about 1,000 women with diagnosed IC. It confirmed that: About two thirds of the women had pain with sexual intercourse. About half found riding in a car painful. IC patients have suicide thoughts three to four times as frequently as members of the general population. Only about half of the IC patients are able to work full time, and those who do work receive $3.41 per hour less than a person without IC with the same schooling and age as the patient.

Philip Held, Urban Institute medical statistician who was the chief researcher on the study and presented it at the NIADDK workshop, concluded that there were 44,000 diagnosed cases of IC in this country, with at least 150,000 more that are undiagnosed. Ratner says that based on the correspondence she receives, she believes the number of diagnosed and undiagnosed cases is closer to half a million.

No men were selected for this survey, although specialists admitted at the workshop that the generally accepted prevalence rate for men -- one man for every 10 women -- probably understates the case. Many men diagnosed with the catch-all "prostatitis" may indeed be suffering from IC.

The survey also found that frequency of urination was a symptom of IC in 90 percent of the women, and that these women had to urinate on the average of once an hour, day and night, around the clock, some needing to do so up to 60 times a day. "This," the authors of the report said, "could result in problems of sleep deprivation." One woman wrote: "I did not sleep for a whole year. I laid on the bathroom floor all night and cried. I am going to the bathroom all the time. It is a nightmare." Says Ratner sadly, "Your entire life becomes circumscribed by the availability of a bathroom."

Other findings: The disorder was previously believed to affect mainly post-menopausal women. However, the survey found that the average age of onset was about 40 and that fully 25 percent of the patients were under age 30. IC patients had 10 to 12 times the number of childhood bladder problems as members of the general population. One third to one half of IC patients reported they received no help from any individual treatment. The time between the onset of symptoms and the diagnosis of IC in three groups of women was 51 months for members of ICA who were surveyed, 24 months for patients designated as recently diagnosed by a group of randomly selected board-certified urologists, and 35 months for a group of recently treated patients also selected by the urologists.

Ratner, who first suffered symptoms in 1984 when she was a third-year medical student, essentially diagnosed herself, and even with a medical school library at her disposal, it took her almost a year. Even so, she recalls, even with photocopies of textbook descriptions in hand, one or another of her 10 physicians told her the strain of med school was getting her down, that she'd just have to learn to live with it, that it couldn't possibly be IC because she was too young, or that she ought to get married and become pregnant. What makes IC so difficult to diagnose and so frustrating to treat is its lack of any identifiable causative agent. In many cases, urologists can identify no physiological symptoms at all -- no bacterial infection, as is found in most urinary tract infections with similar symptoms; only sometimes are ulcers detected; and no particular structural abnormality. Nor does IC respond to any antibiotic or antibacterial agents.

Only one procedure, done under a general anesthetic and usually accompanied by a sometimes temporarily successful surgical stretching of the bladder, has disclosed one finding common to most IC patients -- tiny pinpoint hemorrhages of the bladder wall. Urologists are often reluctant to perform this procedure, which has been considered more invasive than the condition warrants. Other sometimes helpful treatments include the drug DMSO, other chemicals and various surgical techniques.

But frequently, as all treatments fail and the unremitting pain becomes increasingly unbearable, a patient's impatience with the doctor's seeming lack of competence and compassion becomes more overt. The doctor, frustrated himself, may detect a note of hysteria, just enough of a note for him to latch onto it as a possible cause of the disorder and a happy opportunity to refer the patient, who has become a constant reminder of his own inadequacy, to somebody else. A psychiatrist, usually.

Behaviorial psychologist David P. Schwartz, director of the Margaret W. Strong Pain Center in Santa Fe, N.M., reminded members of the workshop that "the history of medicine is full of examples of problems that were called psychological because there was no physical explanation. In fact," he said, "in some of the classic papers on hysteria, if you look back at them, there is a lot of evidence that some of those patients probably had multiple sclerosis or post-concussant syndrome or other physical disorders that simply did not exist in the medical definitions of the day and therefore were defined as psychological or hysterical."

As an example, Schwartz read a translation of a German psychiatric text that appears to describe IC from only a few decades ago:

"Urgent bladder symptoms without any established organic causes would appear to be a psychosomatic illness usually affecting married women in midlife. The majority of patients manifest serious neurotic disorders such as anxiety neuroses, hysteria, phobia and depression . . . Patients have sexual disorders, hysterical personality structure, dominated by Oedipus or phallic problems . . ."

"In other words," said Schwartz, " 'there's nothing really wrong with you; you're just crazy.' "

Couching his talk carefully in apologies for the way the medical profession has "used my profession to explain away" the symptoms, psychologist Schwartz did note that new discoveries in the interactions of mind and body have suggested some approaches to easing IC symptoms.

Most important, though, the patients need "reassurance that the physical disorder is real and legitimate." Urologists, he said, should suggest psychological care "with the frank admission that you can't help them medically, but it is not their fault." Getting Help

More information on this disorder is available from the Interstitial Cystitis Association, P.O. Box 1553, Madison Square Station, New York, N.Y., 10159.