Medically reviewed by Drugs.com. Last updated on Jul 13, 2022.
Kidney cysts are round pouches of fluid that form on or in the kidneys. Kidney cysts can occur with disorders that may impair kidney function. But more often, kidney cysts are a type called simple kidney cysts. Simple kidney cysts aren't cancer and rarely cause problems.
It's not clear what causes simple kidney cysts. Often, one cyst occurs on the surface of a kidney. But more than one cyst can appear on one or both kidneys. Simple kidney cysts aren't the same as cysts that form with polycystic kidney disease. Simple cysts also differ from complex cysts. Complex cysts need to be watched for changes that could be cancer.
Simple kidney cysts are often found during an imaging test for another condition. Treatment usually isn't needed unless simple cysts cause symptoms.
A kidney cyst is a round or oval fluid-filled pouch with a well-defined outline. Kidney cysts typically grow on the surface of a kidney. Some may develop inside the kidney.
Simple kidney cysts typically don't cause symptoms. But if a simple kidney cyst grows large enough, symptoms may include:
- Dull pain in the back or side
- Upper stomach pain
When to see a doctor
Make an appointment with your health care provider if you have symptoms of a kidney cyst.
It's not clear what causes simple kidney cysts. One theory suggests that kidney cysts develop when the surface layer of the kidney weakens and forms a pouch. The pouch then fills with fluid, detaches and develops into a cyst.
The risk of having simple kidney cysts increases as you get older. But they can occur at any age. Simple kidney cysts are more common in men.
Kidney cysts may sometimes lead to complications, including:
- An infected cyst. A kidney cyst may become infected, causing fever and pain.
- A burst cyst. A kidney cyst that bursts causes severe pain in the back or side. Sometimes a burst cyst may cause blood in the urine.
- Blocked urine flow. A kidney cyst that blocks the typical flow of urine may lead to kidney swelling.
Tests and procedures used to diagnose simple kidney cysts include:
- Imaging tests. MRI, CT and ultrasound are imaging tests that are often used to diagnose simple kidney cysts. Imaging tests can help determine whether a kidney mass is a cyst or a tumor.
- Kidney function tests. Testing a sample of your blood may reveal whether a kidney cyst is affecting how well your kidney works.
Treatment may not be needed
If a simple kidney cyst causes no symptoms and doesn't affect kidney function, you may not need treatment. Instead, your health care provider may recommend that you have imaging tests, such as ultrasounds, over time to see whether your kidney cyst changes.
If your kidney cyst changes and causes symptoms, you may choose to have treatment at that time. Sometimes a simple kidney cyst goes away on its own.
Treatments for cysts that cause symptoms
If a simple kidney cyst is causing symptoms, your health care provider may recommend treatment. Options include:
Piercing and draining the cyst, then filling it with a solution. The solution causes scarring and helps prevent the cyst from filling with fluid again. Alcohol or a chemical compound may be used as the solution.
Rarely, to shrink the cyst, a long, thin needle may be inserted through your skin and through the wall of the kidney cyst. Then the fluid is drained from the cyst and filled with a solution to prevent it from reforming.
Surgery to remove the cyst. A large cyst that's causing symptoms may require surgery. To access the cyst, a surgeon makes several small incisions in your skin and inserts special tools and a small video camera.
While watching a video monitor in the operating room, the surgeon guides the tools to the kidney and uses them to drain the fluid from the cyst. Then the walls of the cyst are cut or burned away. Surgery is rarely performed for simple cysts. The procedure is more often used for complex cysts with changes that may be cancer.
Some procedures to treat a kidney cyst may require a brief hospital stay.
Preparing for an appointment
A simple kidney cyst found during an imaging test for another disease or condition may concern you. Talk with your health care provider about what having a simple kidney cyst means for your health. Gathering information may put your mind at ease and help you feel more in control of your situation.
What you can do
Before meeting with your health care provider, prepare a list of questions to ask, such as:
- How big is the kidney cyst?
- Is the kidney cyst new or has it been visible on other scans?
- Is the kidney cyst likely to grow?
- Can the kidney cyst hurt my kidney?
- I have these unexplained symptoms. Could they be caused by a kidney cyst?
- Does the kidney cyst need to be removed?
- What are my treatment options?
- What are the potential risks of each treatment option?
- What symptoms may indicate the kidney cyst is growing?
- Should I see a specialist?
- Are there any restrictions that I need to follow?
- Do you have any printed material that I can take with me? What websites do you recommend?
- Will I need a follow-up visit?
Don't hesitate to ask other questions as they occur to you during your appointment.
What to expect from your doctor
Your health care provider is likely to ask you a number of questions, such as:
- Do you have any symptoms?
- If so, how long have you experienced symptoms?
- Have your symptoms gotten worse over time?
- Do you have any blood in your urine?
- Have you had pain in your back or sides?
- Have you had a fever or chills?
- Do you have any other medical conditions?
- What medications, vitamins or supplements do you take?