Simple Kidney Cyst
A simple kidney cyst is a common, benign fluid-filled sac that forms within the kidney. These cysts have thin, smooth walls and contain clear fluid. They typically cause no symptoms and are often found incidentally during imaging for other reasons. Simple cysts are not cancerous and usually require no treatment unless they grow large or cause discomfort.
What is it?
A simple kidney cyst is a round or oval sac filled with clear fluid that forms in the kidney tissue. These cysts have characteristic features, such as thin walls and no internal solid components. Their appearance on imaging makes them easy to distinguish from complex cysts or tumors.
Ultrasound is often the first test used to identify a simple cyst. CT or MRI may be performed if the cyst has atypical features or if further characterization is needed. When imaging confirms a simple cyst, no additional testing is usually required.
Important to Know
Simple cysts are harmless and do not turn into cancer. They are considered a normal variant, especially in older adults. Only cysts with irregular features—such as thick walls, septations, or solid areas—require further evaluation.
Red flag symptoms include sudden severe flank pain, fever, blood in the urine, or rapid cyst enlargement, which may suggest bleeding, infection, or another underlying condition. These require prompt medical evaluation.