The kidneys remove waste from your blood. They do this by filtering the blood and making urine.
As people get older, sacs filled with fluid can form in the kidneys. These sacs are called "cysts." They are usually small oval or round thin-walled sacs with watery fluid in them.
Kidney cysts are almost always benign (not cancerous). Usually, the cysts don't cause any problems. In fact, people can go through life without even knowing that they have them.
Some people have kidney cysts caused by an inherited disease called polycystic kidney disease (PKD). This disease can cause symptoms such as high blood pressure, pain in the back and side, blood in the urine or frequent kidney infections. Not all people who have PKD will have these symptoms.
Up to 50 percent of people older than 50 years of age have kidney cysts.
Your doctor will ask if you're having any of the following problems:
If you're having any of these problems, your doctor will probably examine you and order lab tests.
Almost all kidney cysts are found on tests that create a picture of your internal organs. These tests include ultrasound, computerized tomography (CT) or magnetic resonance imaging (MRI) scans. Sometimes kidney cysts are found when one of these tests is performed for another reason.
If you're not having any of the symptoms listed in the “Symptoms” section, and your kidney cyst is small, you may not need any treatment. Your doctor might want to check the cyst again with a CT scan in 6 to 12 months.
If you start having problems, your doctor might want you to have a CT or MRI scan of your kidney to see if the cyst is growing.
If the cyst on your kidney is large or if it contains calcifications (hard, stony pieces) or dense tissue, you might need to have CT scans every so often so that your doctor can watch for changes in the cyst.
If a cyst on the kidney isn’t causing any problems, it probably won't need to be removed. If the cyst on your kidney is getting larger or if it’s causing problems, your doctor may send you to a urologist (a doctor who has special training in kidney problems).
Written by familydoctor.org editorial staff