QUESTION: I have had a full feeling in my stomach for more than a year now. Finally, my doctor sent me to a specialist. X-rays showed I have a bezoar in my stomach. The doctor said it can be from undigested fruit fibers. I had stomach surgery in 1981. - Mrs. J.B.

ANSWER: A bezoar is an accretion of undigested matter (plant fiber, hair, for examples). It just lies there like a ball of yarn, sometimes enlarging to the point of interference with functioning of the digestive tract.Certain factors favor bezoars, like stomach surgery, incomplete chewing of food, and deficiency of digestive stomach acid. A bezoar that is reaching dangerous proportions usually provides signals, like your fullness sensation, or nausea and vomiting.

There are various ways to remove a bezoar depending on its composition and size. Sometimes, one can be broken up. Other times, it must be removed surgically.

A low-fiber diet, complete food chewing, and copious amounts of fluid are used in treating patients with bezoars. Incidentally, persimmons are mentioned frequently as one source of fruit fiber conducive to bezoar formation in those prone to the problem.

QUESTION: I recently had surgery for my hemorrhoids, thank goodness! Later, I asked the surgeon about hemorrhoids and what caused them. He said many things, but constipation mainly. Please comment. - H.R.

ANSWER: The doctor was correct. The statement is often made that hemorrhoids are merely rectal area varicose veins. True enough, but that doesn't tell the real story. Any extraordinary abdominal pressure can create the setting for those veins to enlarge. Constipation is high on the list of such causes. And heredity, too, raises its head, for hemorrhoids often run in families. I am sending the hemorrhoids report to you. Others may order by writing: Dr. Donohue/No.16, Box 830, Gibbstown, NJ 08027-9909, enclosing a long, stamped, self-addressed envelope and $2.

QUESTION: Should I have my port wine stain removed? It is on the upper back of my neck and is no appearance problem. I just wondered if it should be removed for health reasons, etc. - O.P.

ANSWER: There is no compelling health reason to remove a port wine stain.

Port wine stains usually begin as pink red blotches and darken to a purple color with years. If a stain is unacceptable, special laser techniques are used to remove them. I suppose the whole world knows of port wine stains today from one of our most famous port wine stain possessors - Mr. Gorbachev of the Soviet Union (on his forehead).

QUESTION: Why are birth control pills used for some women who have endometriosis? - Ms. V.V.

ANSWER: Endometriosis is a misplanting of bits of uterine lining tissue (endometrium) in other (usually pelvic) areas. They often respond to normal hormone production and depending on their location can cause pain during normal hormonal ebbs and flows during cycles.

In this setting, birth control pills can help by interrupting the woman's hormone production. Some women respond better to danocrine, a synthetic form of female hormone. Another treatment is, of course, surgical removal of the misplanted tissue.

Endometriosis is one of the leading causes of female infertility and causes great pain and life disruption. Its causes and treatments are explained in Dr. Donohue's booklet No. 37. For a copy, send a long, stamped, self-addressed envelope and $2 to Dr. Donohue/No. 37, P.O. Box 830, Gibbstown, NJ 08027-9909.

Dr. Donohue welcomes reader mail but regrets that, due to the tremendous volume received daily, he is unable to answer individual letters. Readers' questions are incorporated in his column whenever possible.