Hello Thanks for writing to us Simple cortical cyst in kidney is a benign lesion of unknown etiology arising from renal parenchyma and it rarely causes complications.It may be the reason for omission of small renal cyst in previous reports. Renal cortical cyst is a very common type of kidney cyst and it is a fluid-filled sac. Small cysts generally doesn t causes symptoms and it is found in a routine examination for other issues. When cyst grows larger,patient may feel pain or pressure in back or sides,which often radiates downward. Renal cortical cysts usually doesn t require any treatment. Take Care Dr.Indu Bhushan