What is a kidney mass?
Cysts are the most common kidney masses, explains WUSM St. Louis. These fluid-filled sacs appear in half of people older than 50. Cysts do not generally cause medical problems or comprise any significant risks. Radiologists can easily identify most cysts, most of which do not require any intervention. In some cases, no further observation is necessary. Other cysts, however, are complex and provide more of a challenge. People who have complex cysts receive follow-up monitoring through CT scans or MRI, which look for changes and growth in the cyst.