Cysts are very common after age 50. There are simple and complex cysts. Complex cysts are clinically significant as they can mask an underlying renal cell cancer. If a complex cyst is diagnosed on an ultrasound than the next step is to have CT with iv contrast to evaluate complex cyst. This test has its own set of problems and the iv contrast or dye exposes you to the risk of dialysis if your kidney function is not normal.
Discuss this with your nephrologist. If a CT with contrast is normal and does not show any suspicious lesion within the cyst than the complex cyst can be simply monitored on an annual basis.
I will need your age, creatinine level to answer this question more accurately.