Renal Cyst

Renal cysts are fluid-filled sacs that form in the kidneys. They are commonly discovered by chance during ultrasound, CT, or MRI scans.

Most Common Type of Renal Cysts

Most renal cysts are simple cysts, which are stable and do not usually affect kidney function. Simple renal cysts are a normal occurrence that happens with age. Simple renal cysts are not cancerous, with a risk of malignancy less than 1%. The number and size of simple cysts do not matter for most people, and they typically do not require treatment or follow-up.

Types of Renal Cysts

• Simple Cysts (most common): usually require NO treatment or follow up with doctor, and no further imaging/scans are required. The number and size of these cysts do not matter.
• Complex Cysts: may require further evaluation, close follow-up or surgical removal depending on their characteristics and risk of malignancy.

Most simple renal cysts do not cause symptoms. However, if a cyst grows large enough, it may rarely cause:

• Dull pain in the back or side
• Fever
• Upper abdominal pain

You should consult your doctor if you experience severe or persistent back pain, visible blood in the urine, or if you are found to have parapelvic or complex cysts (Bosniak 2F or higher).

Renal cysts are usually found incidentally during imaging tests such as ultrasound, CT, or MRI scans. Most simple cysts remain stable and do not require repeat scans or specialist review unless symptoms develop or the cysts are complex.

No treatment is required for simple renal cysts, as they do not impact health and are not cancerous. Almost all with simple renal cysts can and should continue their normal activities without restrictions. In rare cases where a cyst causes symptoms or complications, such as infection, rupture, or blockage of urine flow, treatment may involve draining the cyst or surgical removal.

Follow-ups for Simple Renal Cysts

99% of simple cysts remain harmless. There is no need for specialist referral, repeat scans, or further follow-up for most of the patients. This approach is evidence and guideline-based and helps reduce unnecessary referrals due to the benign nature of simple cysts. If you have any concerns or experience new symptoms, consult your primary care doctor.

Will my cyst turn into cancer?

Simple renal cysts are benign and don't become cancerous. Complex cysts have a small risk of malignancy, which is why they require closer monitoring.

Can renal cysts affect kidney function?

Simple cysts typically do not affect kidney function. However, if a person has an underlying polycystic kidney disease, the formation of multiple cysts within the kidney may lead to a loss of kidney tissue over time and may impact kidney function.

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For more information on renal cysts, visit:

• Cleveland Clinic
• Mayo Clinic