Normal kidneys are about the size of a fist. An atrophic kidney is one that has shrunk to an abnormal size with abnormal function. This is also known as renal atrophy.

It’s not the same thing as renal hypoplasia, a condition in which the kidney is smaller from development in the womb and at the time of birth.

The kidneys are located on each side of the lower spine, just under the rib cage. The left kidney is usually a little larger than the right. The left kidney is usually also positioned slightly higher and closer to the heart than the right. One or both kidneys can atrophy, but it may be more likely to occur to the left kidney.

The kidneys filter waste products from the blood and remove excess water from the body. They also play important roles in the regulation of blood pressure.

In the early stages of kidney disease, you might not realize anything is wrong. It can take as much as a 30 to 40 percent loss of function for symptoms to appear. As the kidneys become less able to filter the blood, you may notice:

Other signs of atrophic kidney include:

Your specific symptoms may depend on the reason for the kidney damage.

Kidney damage can start suddenly, such as when the kidney is severely injured or exposed to toxins.

Atrophic kidney may also be due to or associated with another medical condition, such as:

Kidney damage generally occurs over a long period. This can happen because there’s insufficient blood flow to the kidneys.

You may be at higher risk of kidney disease if you have:

Much of your treatment will depend on the cause of the atrophy. Treating the underlying condition may help prevent further damage to your kidney.

Even with an atrophic kidney, your kidneys may still be functioning well enough to get the job done. But if your kidneys are functioning at less than 10 to 15 percent, you’re in kidney failure. That means you need treatment to do the work of the kidneys.

One way to do this is through dialysis.

In hemodialysis, your blood is run through an artificial kidney apparatus called a hemodialyzer that removes waste products. In peritoneal dialysis, a fluid called dialysate is used to fill your abdomen to filter waste in your body through a peritoneal dialysis catheter.

Dialysis helps do the work your kidneys can no longer do. But it’s not a cure. You’ll need to have dialysis several times a week for the rest of your life or until you get a kidney transplant.

You can receive a healthy kidney from a living or a deceased donor. The wait for a suitable kidney can take years, though. After a transplant, you’ll need to take antirejection medications for the life of the kidney.

Atrophic kidney can’t be reversed or cured with diet. But diet plays a vital role in treatment of kidney disease. Here are some kidney-healthy dietary tips:

Cut down on sodium

This will help control your blood pressure. The National Institute of Diabetes and Digestive and Kidney Disease (NIDDK) recommends a diet containing less than 2,300 milligrams of sodium per day. Here are some pointers for reducing sodium:

  • Choose fresh foods rather than packaged foods whenever possible.
  • When using canned foods, rinse before cooking or serving.
  • When shopping, check labels for sodium content.
  • Opt for home cooking in place of restaurants and fast foods.
  • When preparing food, replace salt with other seasonings.

Pay attention to protein

The more protein you eat, the harder your kidneys have to work. But you do need some protein. You can get it from animal products such as:

  • chicken
  • dairy
  • eggs
  • fish
  • meat

Portion size matters, too. A portion of chicken, fish, or meat is 2 to 3 ounces. A portion of yogurt or milk is half a cup. One slice of cheese is a portion.

You can also get protein from beans, grains, and nuts. A portion of cooked beans, rice, or noodles is half a cup. A portion of nuts is a quarter of a cup. One slice of bread is a portion.

Take care of your heart

Heart-healthy foods help keep fat from accumulating in your heart, blood vessels, and kidneys. Incorporate the following tips for a more heart-healthy diet:

  • Skip deep-fried foods in favor of those that are baked, grilled, roasted, or stir-fried.
  • Cook with olive oil instead of butter.
  • Limit saturated and trans fats.

Some good choices are:

  • fruits and vegetables
  • beans
  • low-fat or fat-free yogurt, cheese, and milk
  • fish
  • poultry with the skin removed
  • lean cuts of meat with the fat removed

If kidney function continues to decline, your doctor will make personalized dietary recommendations. Kidney disease can cause phosphorus to build up in your blood, so you might be advised to choose foods that are lower in phosphorus. These include:

  • fresh fruits and vegetables
  • bread, pasta, and rice
  • rice- and corn-based cereal

Phosphorus may be added to packaged food and deli meats, as well as fresh meat and poultry, so be sure to read labels.

Poorly functioning kidneys can also lead to a potassium buildup. Lower-potassium foods include:

  • apples and peaches
  • carrots and green beans
  • white bread, white rice, and pasta

Some higher-potassium foods are:

  • bananas and oranges
  • beans and nuts
  • bran cereal
  • brown and wild rice
  • dairy foods
  • potatoes, tomatoes
  • salt substitutes
  • whole-wheat bread and pasta

Talk to your doctor about your diet. It might also be helpful to consult with a dietitian.

You can live a long, healthy life with only one healthy kidney. However, you’ll need to watch your diet and see your doctor regularly.

In some cases, chronic kidney disease leads to kidney failure. It’s a serious problem if your kidneys are functioning below 25 percent.

For people on dialysis, the average life expectancy is 5 to 10 years, but some may live as long as 30 more years.

The average kidney transplant lasts 12 to 20 years when from a living donor and 8 to 12 years when from a deceased donor.

Of course, much depends on your age and other health considerations. Your doctor can give you more of an idea of your outlook based on your personal situation.

Atrophic kidney can’t always be prevented. But there are some measures you can take to keep your kidneys as healthy as possible.

First, try to prevent those conditions that can damage your kidneys, such as high blood pressure and diabetes. If you already have such a condition, work to keep it under good control.

Your diet should be rich in:

  • fruits and vegetables
  • whole grains
  • low-fat or fat-free dairy products

Limit your intake of:

  • highly processed or fried foods
  • sodium
  • sugar
  • alcohol

Here are a few other tips:

  • Try to exercise for at least 30 minutes on most days.
  • Maintain a healthy weight.
  • Try to get seven to eight hours of sleep every night.
  • Don’t smoke tobacco products.
  • Take medication as prescribed.
  • Monitor your cholesterol levels.
  • Have urinary tract infections (UTIs) treated as quickly as possible.