Hi, Kidney or Renal cysts are round fluid-filled pouches that form in kidneys which sometimes may be associated with serious disorders that may prejudice the normal functioning of the kidneys. But given that your USG report mentions it to be a simple cortical cyst, you don t have to dread as they seldom cause complications and they, by and large, don t entail treatment. You are at peril of acquiring them as you get older and I would want you to be wary of symptoms like fever or severe pain on your lower back or sides as the cyst might get infected because of urine draining into it. You might want to take instant medical assistance in such circumstances. If it is bothering you now, you can discuss it with a Urologist and get it removed surgically. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Ivan R. Rommstein, General Surgeon