Kidney cysts

Kidney cysts are rounded sacs usually filled with fluid. There are two types of cyst – simple and complex.

Simple kidney cysts do not affect kidney function and are common in the older population. Around 20% of people over the age of 50 have kidney cysts (1). Usually, it is difficult to know if you have cysts, as there are rarely physical symptoms. Usually cysts are discovered by accident, during a test or scan for something else. Occasionally, a simple cyst can cause pain if it is pressing on another organ, or can become infected and cause fever, pain and tenderness. Treatment for a simple kidney cyst is only required if it becomes infected or if it affects the function of the kidney or another organ.

A complex cyst can have a more irregular shape than a simple cyst, or thicker walls surrounding the fluid. In general, the larger the cysts and more complex its shape, the more likely it is to develop into a cancer. Complex cysts should be regularly monitored, and removed if necessary.

BHD patients can develop many kidney cysts. While most will not become cancerous, it is important to have regular scans to detect any cancer early and begin treatment as soon as possible.


1. Simple Kidney Cysts | NIDDK [Internet]. [cited 2021 May 14]. Available from:

Last Updated: May 2021
Review date: May 2024