Kidney function declines with age in some people. A heart-healthy diet and lifestyle will protect your kidneys. Once kidney function reaches a certain low level, medication and other steps to protect the kidneys may be necessary.

Chronic kidney disease (CKD), a condition found in about half of U.S. adults older than 75, has come to be considered by many people as an almost "normal" part of aging, because it is so widespread. But a recent study suggests that CKD and its complications are associated with a higher risk of death at any age, and that preventing CKD or at least slowing its progress is not only possible, but should be a priority for everybody. The study was published online Oct. 30, 2012, in The Journal of the American Medical Association.

CKD involves the loss of kidney function over time, and one of the indicators of CKD is the amount of protein in the urine. Because of the link between CKD and higher death risks, people who start to experience kidney problems should take all necessary steps to make lifestyle changes and follow recommended treatment plans. CKD is also a risk factor for cardiovascular complications. Among the main preventive steps you can take are to quit smoking, drink alcohol in moderation (if at all), and eat a healthy diet that's low in saturated fat.

Ask the doctor

Do I really need a statin?

Q. I am 71 years old, have chronic kidney failure, and am on dialysis.  I know my overall outlook is not good, and I wonder whether it is worth it to take a statin to control my cholesterol.

A. It's a good question. We have a tendency in medicine to prescribe statins whenever we see elevated cholesterol levels—even in people who might have conditions that make it less likely they will benefit from cholesterol reduction. That being said, the risk of cardiovascular complications is very high in people with kidney disease, and there are pretty good data that lowering cholesterol can reduce cardiac deaths and complications from atherosclerosis by about 20%. Side effect rates are so low that I think this medication is probably worthwhile for you.

Older people with chronic kidney disease often develop heart disease, since atherosclerosis can affect the arteries of both organs.

Q. I am 72 years old, and have had diabetes and high blood pressure for about 15 years. I thought these problems were pretty well controlled, but I recently learned that my kidney function is declining. My creatinine level is now 2.2 milligrams per deciliter (mg/dL). How serious is this?

A. Kidney damage is one of the most common and serious consequences of both diabetes and hypertension. Ask your doctor what your glomerular filtration rate (GFR) is. This test measures how much blood your kidneys filter every minute. If your GFR is 60 or higher, your kidney function is still normal; a lower GFR level means your kidney function bears close watching.

Q. My potassium level is high, and my physician stopped the medication that has successfully controlled my blood pressure for years, lisinopril. What is the danger from high potassium, and why is lisinopril a problem?

A. Potassium is important for the electrical activity of the cells in your heart, and levels that are below 3.4 milligrams per deciliter (mg/dL) or above 5.0 mg/dL can lead to heart rhythm problems that may be life-threatening. Some medications used for high blood pressure, heart failure, and other cardiovascular problems can affect potassium levels, so levels must be checked often.

Q. During a pelvic ultrasound to evaluate uterine fibroids, a radiologist found a cyst in one of my kidneys. Should I be concerned about kidney cancer?

A. Kidney (or renal) cysts are fluid-filled sacs in the kidney that rarely cause symptoms and are usually harmless. They are quite common, and the likelihood of having one or more of them increases as we age. Cysts may be "simple" or "complex." Simple cysts are thin, round sacs with clear fluid, and they are not cancerous. Complex cysts may have thick walls, several lobes, and flecks of calcium or solid components. They are also usually benign, but need further evaluation to be sure they do not contain cancer. Most often a CT scan or MRI will help a urologist or renal expert recommend a strategy of watchful waiting, biopsy, or removal of the cyst. Occasionally, a benign cyst grows large enough to affect the function of the kidney or cause pain. A cyst may also become infected or bleed, causing fever, pain, or blood in the urine (hematuria). In that case, the cyst may need to be removed or drained.

Q. In the past you have discussed blood in the urine. I don't have that problem, but during my annual checkup last week, my doctor found protein in my urine. Is it a serious problem? And what should I do about it?

A. Your kidneys have many functions, ranging from helping to regulate your blood pressure and stimulating the production of red blood cells to converting vitamin D into its active form. But their best-known job is to rid your body of excess fluids and metabolic waste products. To do that, the blood that flows into each kidney passes through about one million tiny vascular filters called glomeruli.

Working to lower blood pressure, cholesterol, and blood sugar and to ease inflammation definitely helps the heart. It is also good for the kidneys. Now, Japanese researchers have found that treating atrial fibrillation (AF), the fast and uncoordinated beating of the heart's upper chambers, may improve the kidneys' filtering abilities.

In a study, 386 people with AF and mildly reduced kidney function received a catheter-based procedure called ablation to restore normal atrial beats. The tip of the catheter destroys (ablates) small patches of tissue in the left atrium that generate the electrical signals that incite AF (see illustration).

Average life span goes down; rehospitalization rates go up.

A silent condition like high blood pressure is sneaky. You don't feel it, and it generally doesn't cause any outward signs or symptoms. Yet it relentlessly causes problems in the arteries, heart, kidneys, and elsewhere.