A renal cyst is a fluid-filled sac in the kidney, and many are simple and harmless.
Many renal cysts cause no symptoms, but some people may have side pain, blood in the urine, infection, or pressure effects if the cyst is large or complicated.
Imaging helps show whether the cyst is simple or complex, whether it has suspicious features, and whether follow-up or further testing is needed.
Ultrasound and CT help determine whether the cyst looks simple, complex, or suspicious enough to need closer follow-up.
Simple cysts often need no treatment, while complex or symptomatic cysts may need further imaging or specialist review.
This entry explains the finding. The next step is having a radiologist interpret your specific scan, not a general definition.