DEAR DR. DONOHUE: My 83-year-old mother’s biggest health issue is hemorrhoids. She strains when having a bowel movement, and the result is bleeding and inflammation. She has external and thrombosed hemorrhoids.

ANSWER: Hemorrhoids are dilated rectal blood vessels a bit like leg varicose veins. That’s not exactly true, but it gives people a picture of what’s going on. Straining to pass hard stool is one of the causes of hemorrhoids. I’m not clear why your mother is straining if her stools are not solid.

The two kinds of hemorrhoids, internal and external, are distinguished by their location. Internal hemorrhoids are higher up in the anal canal, and the external ones are close to the anal opening. External hemorrhoids are covered by tissues that have an abundant nerve supply, so they can be most painful, especially when there is a clot in them – a thrombosed hemorrhoid. The covering of internal hemorrhoids has few nerves, so these hemorrhoids don’t cause as much pain. Both bleed; internal hemorrhoids bleed more profusely.

A thrombosed hemorrhoid can often be taken care of in the doctor’s office by incising it and removing the clot.

For external hemorrhoids, sitting in a bathtub filled with water to a level that bathes the hemorrhoids keeps the area clean and relieves pain. This is a sitz bath and should be done two or three times a day. Keeping the area clean also alleviates itching. An antihistamine before bedtime can further reduce itching and can provide for an undisturbed night of sleep.

The choices for internal hemorrhoids are many. Encircling the hemorrhoids with rubber bands, injecting them with solutions that make them shrivel and coagulating them with infrared light are procedures that can be readily done on a person who cannot tolerate surgery.

DEAR DR. DONOHUE: I am a 75-year-old woman. I have three things of interest to me. I was diagnosed in the fall of 2006 by an MRI with a tumor called a schwannoma on the right side. One year later, another MRI showed no change. It was explained that this is a nonmalignant tumor around a nerve. Is it harmful to have an MRI each year? Will you elaborate on this kind of tumor? I had shingles in January 2006, on the left-side waist area. I had an injection for it and wonder if the injection caused the schwannoma. Did it? – M.M.

ANSWER: A schwannoma is a slow-growing, noncancerous tumor arising from Schwann cells. Schwann cells are attached to nerve roots and produce myelin, a substance that insulates those roots so they can conduct electrical signals to other nerves and to target organs. Yours hasn’t grown in a year. It’s unlikely to ever reach a size where it has to be removed.

The injection you got for your shingles had nothing to do with the schwannoma.

An MRI – magnetic resonance imaging scan – emits no radiation. It takes pictures with magnets. It presents no health threat.

DEAR DR. DONOHUE: I have been taking glucosamine and chondroitin daily for months for an arthritic knee without any benefit. Am I wasting money on this stuff? Do any studies exist on these remedies? – P.K.

ANSWER: Glucosamine comes from the outer shells of crabs, lobsters and shrimp. It’s said to stimulate the synthesis of cartilage that covers joints and protects them.

Chondroitin comes from shark or bovine cartilage. It’s a natural constituent of cartilage and keeps it hydrated.

Some people have obtained pain relief by using these products. Others have not. Many studies have been done and have produced conflicting results. If you aren’t feeling any better after months of use, then stop using them.

DEAR DR. DONOHUE: You wrote about angina and said people take medicines that ease the heart’s burden and open up clogged arteries. I would like to know what the medicines are that open up clogged arteries. – A.C.

ANSWER: That was a bad choice of words on my part. The medicines I had in mind don’t get rid of artery clogs, but they dilate arteries so that more blood can get through them. These drugs include nitrates, nitroglycerin and calcium channel blockers like Cardene, Procardia, Norvasc and many others.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him at P.O. Box 536475, Orlando, FL 32853-6475.