Kidney Cysts | Overview


What do the kidneys do?

The kidneys remove waste from your blood. They do this by filtering the blood and making urine.

What are kidney cysts?

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.

How common are kidney cysts?

Up to 50 percent of people older than 50 years of age have kidney cysts.


Evaluation of Incidental Renal and Adrenal Masses by JC Higgins, CDR, MC, USN and JM Fitzgerald, MAJ, USAF, MC (American Family Physician January 15, 2001,

Written by editorial staff

Reviewed/Updated: 03/14
Created: 09/00