Please note: This information was current at the time of publication. But medical information is always changing, and some information given here may be out of date. For regularly updated information on a variety of health topics, please visit, the AAFP patient education website.

Information from Your Family Doctor

Kidney Cysts


Am Fam Physician. 2005 Jan 1;71(1):130.

What do the kidneys do?

Kidneys remove waste products from your blood. They do this by filtering the blood and making urine. The waste products are removed in the urine.

What are kidney cysts?

Sacs filled with fluid can grow in the kidneys. These are called cysts. They are like tiny water balloons. Kidney cysts usually are not serious. In fact, people can go through life without knowing that they have them. Up to one half of people older than 50 years have kidney cysts.

How are kidney cysts found?

Almost all kidney cysts are found when your doctor does an ultrasound, CT (short for computed tomography), or MRI (short for magnetic resonance imaging) test. These tests take pictures of the inside of your body. Your doctor usually wants to do these tests because of other health problems. The cysts are called “incidental” because they are found while the doctor is looking for something else.

What will my doctor do if I have a kidney cyst?

First, your doctor will ask if you are having pain on your side between your ribs and your hip, pain in your belly, a fever, urination more often than usual, or blood in your urine. If you are having any of these problems, your doctor will probably examine you and order lab tests.

If you are not having any of those problems and your kidney cyst is small, you probably do not need any treatment. Your doctor might want to check the cyst again with another CT scan in six to 12 months to see if the cyst is growing.

If your kidney cyst is large or if it contains hard, stony pieces, you might need to have CT or MRI scans every so often so that your doctor can watch for changes in the cyst.

Will I need surgery to remove a kidney cyst?

Probably not. Most kidney cysts do not need to be removed. Your doctor may send you to a urologist (a doctor with special training in kidney problems) if your cyst gets bigger or starts causing problems.

This handout is provided to you by your family doctor and the American Academy of Family Physicians. Other health-related information is available from the AAFP online at

This information provides a general overview and may not apply to everyone. Talk to your family doctor to find out if this information applies to you and to get more information on this subject.


Copyright © 2005 by the American Academy of Family Physicians.
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