It's in the wall of your bladder - not your head.

If you're one of those persons whose bladder problem has defied all efforts at diagnosis, leaving your doctor with the conclusion that it must be "all in your head," take heart. You're not alone, and it's not in your head.

Some 450,000 persons in this country are afflicted with interstitial cystitis, a chronic, debilitating condition that seems to defy the diagnostic efforts of many physicians. It afflicts women 10 times more frequently than men, causing its victims to get up as often as 10 times in the night to urinate, with pain in the pelvis, bladder, and vagina.

The pain and the frustration of negative tests for every kind of bladder problem often bring afflicted patients to thoughts of suicide.

Urine cultures, cystoscopy, tests of the bladder nerves, and every other diagnostic procedure are regularly negative in these patients--yet the disease is very real. Because the inflammation that produces the symptoms is within the wall of the bladder (hence its name), it is out of reach of the usual diagnostic tests for bladder disease.

The cause of the disease is unknown--possibly a disorder of the immune system, or some kind of allergic reaction. Many physicians do not recognize it and attempt to treat it with antibiotics, without success. Some patients have seen as many as 10 doctors over a period of years without obtaining relief.

Treatment includes removing caffeine, alcohol and spicy fluids from the diet. Nonsteroidal inflammatory drugs (NSAIDs), such as ibuprofen, is, many fine people have been coping with their disease for a lot longer than the six-month maximum set by the CDC.

The drug is ampligen, and in the 92 severely ill chronic fatigue patients to whom it was given in early trials at a number of medical centers, the results were dramatic indeed. Intravenous administration of the drug twice a week for 24 weeks produced "global improvement" ( in the words of the researchers), compared to no change whatsoever in the control group of like patients.

Patients who had to spend most of their time in bed were able to go back on a normal schedule, and all patients used fewer anti-inflammatory and nerve drugs and spent less time in the hospital.