DEAR DR. DONOHUE: My feet and ankles can swell so badly that I have trouble getting my shoes on and off. My doctor shrugs when I ask why they’re swollen. All he says is to stop using salt. Can you tell me what causes it and what to do for it? – M.E.

ANSWER: Such swelling is called edema (uh-DEE-muh), and it comes from tissues that are soaked with fluid. It takes several quarts/liters of excess fluid before swelling is even noticeable, so when a person has swollen ankles and feet, that person has retained a considerable amount of fluid.

Causes are many. Heart failure is a prominent one. Untreated high blood pressure is another common cause. Failing kidneys make the body retain fluid and produce swelling. Liver cirrhosis is another cause. Obstruction of leg veins makes leg blood vessels leak fluid into tissues. So does keeping the feet dangling down when sitting for prolonged periods of time. In that position, gravity draws fluid out of blood vessels.

An often-underappreciated cause is commonly used medicines. Anti-inflammatory medicines like ibuprofen can do it, as can cortisone drugs. Calcium channel blockers are a family of popular medicines for blood pressure and angina. They can give rise to swollen ankles. Some names are Calan, Procardia and Cardizem.

The only approach to treatment is finding the cause. Some general measures can help you reduce swelling. Do go easy with your use of salt. When you sit, prop your legs up, and the higher and the longer you prop them, the better.

Wearing elasticized hose compresses swollen tissues by forcing fluid back into the circulation. Water pills are usually a part of treatment.

The booklet on edema and lymphedema goes into greater depth on these topics. Readers can order a copy by writing: Dr. Donohue – No. 106, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.50 U.S./$6.50 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: My 12-year-old niece has had swelling of her leg, ankle and foot for the past two years. X-rays and scans of her legs are normal. We would like to obtain a second opinion but don’t know what type of specialist to see. Your thoughts, please? – N.G.

ANSWER: One possibility for your niece’s swelling is lymphedema, a disruption of the lymph vessels. Those vessels siphon fluid that bathes tissues and cells and return it to the circulation. If there is an obstruction in those channels, fluid stays in the tissues and causes them to swell.

Such a disruption of lymphatic channels can be present from birth but not cause any trouble until early adolescence or even adult life.

Women who have had lymph nodes and lymph channels removed during surgery for breast cancer can develop a swollen arm postoperatively. That is another form of lymphedema.

There are treatments for lymphedema. Therapists who have had special massage training can often reduce the amount of fluid in swollen, lymphedematous limbs.

The kind of doctor your niece should see is a vascular surgeon.

DEAR DR. DONOHUE: A friend tells me it is not healthy to sleep under an electric blanket because the electric current could cause cancer. Is this nonsense? – J.R.

DEAR DR. DONOHUE: On the radio I heard about a study that dealt with digital alarm clocks close to one’s head as possibly leading to brain cancer. What do you think? – R.G.

ANSWER: I have heard both allegations for many years, and I have seen arguments on both sides. I use an electric blanket and a digital alarm clock. I intend to keep using them. I don’t find any substantial evidence that either constitutes a danger. That’s my opinion, and that’s all it is – my opinion.

DEAR DR. DONOHUE: What’s the difference between diabetes 1 and 2? Doesn’t diabetes mean high blood sugar? Do 1 and 2 both have high blood sugar? I want to know about diabetes because my sister, age 49, has just come down with diabetes 2. What are my chances of getting it? – K.K.

ANSWER: All diabetes varieties feature high blood sugar. Differentiating them into types (there are more than two types) is important because the various types have different causes, different treatments and different implications.

Type 1 diabetes used to be called juvenile diabetes or insulin-dependent diabetes. It most often comes on in young life – but not always, so the “juvenile” designation is not appropriate. It almost always demands treatment with insulin, so the insulin-dependent tag is not entirely incorrect, but it can be misleading. Type 1 diabetes is the result of an autoimmune attack on the pancreas cells that make insulin. Without insulin, blood sugar rises. In North America there are around half a million type 1 diabetics, with close to 30,000 new cases added yearly.

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 or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.