Kidney Cysts What do the kidneys do? The kidneys remove waste products 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 cancer). 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 experience these symptoms. How common are kidney cysts? Up to 50 percent of people older than 50 years of age have kidney cysts. How are kidney cysts found? Almost all kidney cysts are found on tests that create a picture of your insides. These tests include ultrasound, computerized tomography (CT) scans or magnetic resonance imaging (MRI) exams. A doctor may notice that the patient has a kidney cyst when he or she does one of these tests because of another problem. Benign cysts that are found when a doctor is looking for something else are called "incidental cysts." If I have a kidney cyst, what will my doctor want to do? First, your doctor will ask if you're having any problems such as pain on your side between your ribs and your hip, pain in your belly or back, a fever, frequent urination or blood in your urine. If you're having any of these problems, your doctor will probably examine you and order lab tests. If you're not having any of those problems 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. Remember that most people with kidney cysts never have problems and never need extra CT scans. If your kidney cyst 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. To get more information about the cyst, your doctor might also want you to have an MRI scan. Will I need surgery to remove a kidney cyst? Probably not. Most kidney cysts are harmless and don't need to be removed. Your doctor will send you to a urologist (a doctor with special training in kidney problems) if your kidney cyst keeps getting bigger, if you have problems because of the cyst or if there is any concern that the cyst might be cancerous. Other Organizations National Institute of Diabetes and Digestive and Kidney Diseases http://www.niddk.nih.gov 31 Center Drive, MSC 2560 Bethesda, MD 20892-2560 National Kidney Foundation http://www.kidney.org 30 East 33rd Street New York, NY 10016 800-622-9010 American Kidney Fund http://www.akfinc.org 6110 Executive Blvd, Suite 110 Rockville, MD 20852 800-638-8299 Source Evaluation of Incidental Renal and Adrenal Masses (American Family Physician 01/15/2001, http://www.aafp.org/afp/20010115/288.html)