DEAR DR. DONOHUE: For almost all this past year, I have had off-and-on pain in my lower abdomen. My doctor put me through all sorts of tests, including scans, but nothing turned up. Now I’m seeing a gynecology doctor, who thinks I have endometriosis. I’m not at all familiar with this. What does it entail? — G.D. A: The endometrium is the lining of the uterus. Every month, in preparation for nurturing a fertilized egg, it grows. If no egg is fertilized, the lining is shed during the menstrual period.

Endometriosis is uterinelining tissue in places outside the uterus. It can be in or on the bladder, the bowel, the rectum, the ovary or the dropcloth (the peritoneum) that covers many abdominal and pelvic organs. Just like the endometrium in the uterus, this displaced endometrium grows every month under the influence of monthly hormones. The growth causes pain. Most often, the pain is felt in regions below the bellybutton. As many as 5 percent of women between the ages of 15 and 45 have it.

The endometrial tissue reaches these distant sites by passing through the fallopian tubes, the tubes through which eggs reach the uterus.

A doctor with a laparoscope can see the displaced tissue. A laparoscope is a telescopelike device inserted into the pelvic cavity through a small skin incision.

If the amount of endometriosis isn’t extensive and if the pain isn’t disabling, birthcontrol pills, along with antiinflammatory drugs like ibuprofen, often can end symptoms. For more widespread disease, medicines that stop the production of estrogen dry up the transplanted endometrium. Sometimes, surgical removal of the displaced endometrium is necessary. Often, that can be done with a laparoscope and a laser or surgical instruments passed into the pelvis through small incisions. The woman frequently returns home the same day.

c. North America Syndicate