DEAR DR. DONOHUE: My wife is 63, not overweight and not diabetic. She was recently diagnosed with chronic kidney disease, CKD. Her glomerular filtration rate is 49. Her doctor indicated she should limit sugar, lower her LDL cholesterol and keep her blood pressure down.

This came as a surprise. Can you help us understand the causes, treatment and prognosis of her condition? – E.S.

ANSWER: Chronic kidney disease affects 20 million Americans. Often, it develops insidiously, without any signs or symptoms until routine lab tests indicate the kidneys are not functioning up to par. Invariably, the news comes as a shock.

The causes are many. Diabetes, hardening of the kidney arteries, high blood pressure, artery inflammation, kidney inflammation, polycystic kidney disease and scleroderma are just a few of the possible causes. In some instances, identifying a cause is impossible. The end result for all is the same. The kidneys can’t maintain the optimum environment for the body and its organs. Protein is lost in the urine. Blood pressure rises, and the body becomes more acidic. Blood potassium often goes up. People can become nauseated and lethargic. Anemia is a common consequence. Your wife is not near the stage of these symptoms.

There are five stages to CKD, based on glomerular filtration rate. Glomeruli are the kidney filters. Your wife’s glomerular filtration rate puts her in stage three.

The rate of progression to stage five is highly variable and unpredictable. Your wife might never reach that stage.

The focus of her attention should be prevention of heart disease, which is what usually leads to the death of people with CKD. She has to watch her cholesterol by adhering to a low-fat, low-cholesterol diet; she has to control her blood pressure meticulously; she should restrict salt intake; she might, in time, need to cut back on protein. If she progresses rapidly, dialysis is an option, as is possibly kidney transplantation.

DEAR DR. DONOHUE: I suffer from acid reflux, and it affects my asthma. I also have a hiatal hernia. My gastroenterologist recommends doctoring with medicine. A surgeon’s opinion is that the asthma will not get better without surgery. What is your opinion? – L.W.

ANSWER: The upward splashing of stomach acid and stomach juices into the esophagus and higher can induce asthma attacks. The upward splashing is gastroesophageal reflux disease, GERD (heartburn). Often, that can be controlled with medicine. If it can’t, then surgery should be considered.

I’d take the medicine route first. If it doesn’t work, then you can consider the surgical approach.

The booklet on GERD discusses it and its complications in depth. Readers can order a copy by writing: Dr. Donohue – No. 501, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: I read your article on the T value of osteoporosis, and I am very confused. You wrote: “A T-score of .5 or less indicates osteoporosis. A score of -1 to -2.5 is osteopenia – not osteoporosis, but on the way to becoming osteoporosis.”

Being a mathematician, any negative numbers such as -1 to -2.5 are less than .5. Please help. – J.S.

ANSWER: My throat tightened when I read your letter. You are correct. I looked up my copy of that item, and it says “A T-score of -2.5 or less indicates osteoporosis.” The “-2” is missing in your paper. It must have gotten lost on the way.

These T-scores are obtained from a bone density test.

DEAR DR. DONOHUE: I lost vision in my left eye years ago due to a brain tumor. Now I see flashing colors off to one side in my right eye. The eye doctor said it is caused by an aura. Please explain what an aura is. I can’t find it in any of my books. – P.K.

ANSWER: In medicine, an aura (OR-uh) is a warning sign.

The condition where an aura is most often found is migraine headache. About 15 percent of people who get such headaches experience a warning that the headache is about to occur. They see a C-shaped jagged line off to one side of their vision, and often, it is multicolored and flashing. It lasts anywhere from 20 to 25 minutes, and then the headache strikes.

A few people have the aura without getting the headache. Then the aura is called a migraine equivalent.

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. Readers may also order health newsletters from www.rbmamall.com.