Renal cyst: Meaning in a Radiology Report

Also written as: kidney cyst, simple renal cyst, renal cortical cyst, parapelvic cyst

A renal cyst is a fluid-filled sac in the kidney. Simple cysts are very common, especially with age, and are harmless.

What it means

A renal cyst is a round pocket of fluid in the kidney, usually with a thin, smooth wall. Simple cysts become more common with age and are found in many people over 50. They rarely cause symptoms. Some sit near the kidney's center (parapelvic cysts) and can look like a swollen drainage system. Complex cysts have extra features, such as inner walls, thick edges, calcium or solid parts.

When it matters

Simple cysts are harmless and need no follow-up. Cysts with extra features are graded with the Bosniak system. Classes I and II are benign. Class IIF is usually rechecked with imaging for several years. Class III is uncertain and class IV is likely cancer, so a urologist usually reviews both. A cyst that cannot be judged on one scan may need a CT or MRI with contrast. Many cysts in both kidneys can point to an inherited condition.

Questions to ask your doctor

Is my cyst simple, or does it have features that need a Bosniak class?
Does this cyst need any follow-up scans?
Could the cyst be causing my back or side pain?

General information, not medical advice. What a finding means for you depends on your symptoms, your history and the images themselves, so talk your results through with a doctor.