Once again Bruce has given great information. One thing I would suggest: Your vet might want to do an Intravenous injection of dye and take an x-ray afterwards to see if the kidney without the cyst has normal blood flow. I have seen a couple of cases where the blood work before sx was normal the cystic kidney was removed and the pet went immediately into renal failure after surgery. Because even though the kidney had a big cyst on it: that was the normally functioning kidney, the other one did not work well at all. This test is often called an IVP. Just some food for thought. but besides Bruce is right, usually these cysts are nothing to worry about. I see them all the time. Benjamin A. Otten, DVM Avian & Exotic Pet Medicine The Animal Medical Center [Posted in FML issue 3359]