Renal cyst
Read Your Scan Editorial Team·Last updated
Written from published radiology references and reviewed for plain language. Not written or signed by a physician, and not a diagnosis. How we write these pages →
In plain language
A fluid-filled pocket on the kidney. Simple kidney cysts are extremely common and usually harmless. Your doctor decides whether any check is needed.
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Where you'll see this
This wording turns up on Abdominal CT reports — CT imaging of the abdomen. An abdominal CT shows the liver, gallbladder, pancreas, spleen, kidneys, bowel, blood vessels, and lymph nodes in fine detail. Doctors order it for abdominal pain, to look into a suspected stone, infection, or blockage, or to check known findings. Because it is so detailed, it often notes small, harmless things by chance. The report describes what the images show; your doctor reads it together with your symptoms and other results.
Questions worth asking your doctor
- What was the main reason for this CT, and did it answer that question?
- Were any findings incidental, and do any of them need follow-up?
- If a stone or cyst was seen, does it need treatment or monitoring?
- Do the results change my current care or medications?
- Is there anything I can do about findings like fatty liver?
How common is this?
Simple renal cysts are among the most common incidental findings in abdominal imaging, increasing markedly with age, and are present in over half of people over 50 when scanned. They are fluid-filled sacs that develop in the kidney and are considered a benign, normal part of kidney aging in the vast majority of cases.
When should I worry?
A simple cyst with thin, smooth walls and clear fluid is almost always benign and needs no further workup. Cysts described as "complex," with thick walls, internal septations, solid components, or contrast enhancement, are a small minority that need closer evaluation, typically using the Bosniak classification system, to determine if follow-up imaging or referral is needed.
What happens next
Simple cysts rarely need any treatment and are typically not even followed up unless they're very large or causing symptoms like flank pain. Complex cysts may prompt additional imaging or, in a minority of cases, biopsy or surgical evaluation, depending on their Bosniak category and how suspicious their features appear.
Frequently asked questions
- Is a kidney cyst the same as kidney cancer?
- No, the vast majority of renal cysts are simple, fluid-filled sacs that have essentially no cancer risk. Radiologists specifically describe the cyst's features to distinguish the rare complex cyst that warrants further evaluation from the common simple cyst that does not.
- Do kidney cysts need to be removed?
- Almost never. Simple cysts are left alone unless they grow very large and cause symptoms. Even then, drainage is preferred over removal. Only the most suspicious complex cysts, those with solid or enhancing components, are considered for surgical intervention.
- Can a kidney cyst cause pain?
- Small cysts rarely cause any symptoms at all. Larger cysts, typically over 4 cm, can occasionally cause a dull ache or flank discomfort, and rarely a cyst can rupture or bleed, causing sudden pain. Most cyst-related pain settles with conservative care.
Other words on the same report
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