If you have a kidney cyst, you may have concerns about what it means for your overall health. Kidney cysts (also called renal cysts) are sacs that form in the kidneys. These cysts range in size and can be as small as a pea or as large as a golf ball.

Kidney cysts are quite common, particularly as you age. It’s estimated that 1 in 10 people have a cyst in one or both kidneys. And as many as 1 in 5 people over the age of 50 have them.

Are kidney cysts a sign of kidney cancer?

Most kidney cysts are simple kidney cysts. They are benign (not cancerous). These round or oval-shaped sacs have thin walls that hold a clear, watery liquid. 

Complex kidney cysts have the potential to develop into kidney cancer. These cysts are irregular in shape. Their thick walls may contain liquid and solid substances.

What is polycystic kidney disease (PKD)?

Some people inherit a gene from a parent that causes many cysts to form in the kidneys. This condition is polycystic kidney disease (PKD). Although these cysts don’t cause cancer, they can make the kidneys too large and affect kidney function.

People with PKD are at risk for kidney failure. When you have kidney failure, the kidneys struggle to remove waste from the body. People with severe kidney failure may need a kidney transplant or use a dialysis machine to filter blood. Nearly half a million Americans have PKD.

PKD is different from acquired cystic kidney disease (ACKD). ACKD affects people who are on dialysis due to chronic kidney disease. The condition causes multiple cysts to form in the kidneys. These cysts are often harmless, don't cause damage to the kidneys, and don’t require treatment. About 6 in 10 people who are on dialysis for 2 to 4 years develop ACKD.

What causes kidney cysts?

Experts aren’t sure why some people develop kidney cysts. Something may block the tubules (tiny tubes) that collect urine, causing small sacs to form. If these sacs separate from the tubule, simple kidney cysts may form.

What are the risk factors for kidney cysts?

Anyone can have kidney cysts. Some infants are born with them. But older adults, especially those who smoke, are more likely to have kidney cysts. Men are twice as likely as women to have kidney cysts.

Certain health problems may also increase your risk of kidney cysts, including:

• chronic kidney disease (gradual loss of kidney function that may lead to dialysis)

• high blood pressure

• medullary cystic kidney disease (inherited condition that causes scarring and cysts in the kidneys)

• tuberous sclerosis complex (inherited condition that forms noncancerous tumors on the brain and organs)

• Von Hippel-Landau disease (inherited condition that causes noncancerous tumors to form throughout the body)

What are the symptoms of kidney cysts?

Most simple kidney cysts don’t cause symptoms. You may find out you have a cyst when having imaging tests for another problem like a kidney stone or a urinary problem.

Sometimes, simple or complex kidney cysts grow too large, bleed, or get infected. You may have symptoms like:

• blood in urine (hematuria)

• dull ache or pain in the side or back

• fever

• frequent or urgent need to urinate

• pain in the upper abdomen

• tenderness or pain between the ribs and pelvis

Problems caused by kidney cysts are similar to symptoms of kidney cancer, so it’s important to see your doctor if you have any symptoms.

How do you know if a kidney cyst is cancerous?

Your doctor may perform imaging tests like ultrasounds, CT scans, or MRIs to determine if a cyst is simple or complex. A complex kidney cyst is likely to have solid substances inside the sac. A simple kidney cyst will be all liquid. You may also get blood and urine tests to check kidney function.

You may get a CT scan or MRI that uses an IV contrast dye. Cancerous cysts will absorb most of this dye and appear more brightly on the scan.

Doctors rarely biopsy a cyst to rule out or diagnose kidney cancer. That’s because 20% of kidney biopsies give false negative results (you have cancer, but the test indicates that you are cancer-free). As a result of this error, you might not get lifesaving kidney cancer treatments. Kidney cancer could spread to other organs (metastatic kidney cancer), making the cancer more difficult to treat.

How are kidney cysts treated?

Simple kidney cysts rarely need treatment unless they cause pain, block urine flow, or worsen high blood pressure. Even complex kidney cysts may not need treatment — at least not right away.

Because 1 in 4 kidney masses are not cancerous, your doctor may choose to take a watchful waiting (active surveillance) approach. If the cyst is smaller than 1.2 inches, you may get imaging scans every 3 to 6 months to see if the cyst grows or changes. If tests don’t detect any changes after one year, you may get less frequent scans.

Treatments for kidney cysts include:

• Sclerotherapy: Your doctor uses ultrasound images to guide a thin needle into the cyst and drain the fluid. An alcohol solution is injected into the cyst to harden and shrink it. This step prevents fluid from filling up the sac again. Sclerotherapy is typically an outpatient procedure, which means you go home the same day.

• Laparoscopic surgery: Your doctor uses a laparoscope (thin tube with a light and video camera on the end) to surgically treat the cyst through small incisions. Treatment involves draining the cyst and then removing or burning away the sac. This procedure requires hospitalization. 

• Partial nephrectomy: During a partial nephrectomy, your doctor surgically removes the section of the kidney that has the cyst.

From the community: “I do not have personal experience with this, there seems to be an increasing understanding that some cysts can go from simple cysts to complex cysts to tumors. Kidney cancer is slow growing for the most part, so this shift may happen over many years. The cysts may be present for years, and only as its shift into malignancy and causes pain or is found on a CT scan--usually while looking for another issue--will it be found. …However, there are risks in removing cysts, as with any medical procedure, so there is likely to be little support for doing this, when those cysts may never become a problem. As newer techniques to do needle biopsies or such become more common, and there can be an examination of the molecular characteristics of these cysts, they may be seen as precursors to kidney cancer. And still may be best left alone, indolent and essentially not shifting into cancerous states.” - Inspire member

Sources

• Simple kidney cysts. Cedars Sinai.

• Kidney cancer diagnosis. Johns Hopkins Medicine.

• Kidney cysts. Mayo Clinic. July 2020.

• Acquired cystic kidney disease. National Institute of Diabetes and Digestive and Kidney Diseases. August 2015.

• Definition and facts for kidney stones. National Institute of Diabetes and Digestive and Kidney Diseases. May 2017.

• Kidney failure. National Institute of Diabetes and Digestive and Kidney Diseases. January 2018.

• Polycystic kidney disease. National Institute of Diabetes and Digestive and Kidney Diseases. January 2017.

• Simple kidney cysts. National Institute of Diabetes and Digestive and Kidney Diseases. June 2019.

• I have complex cysts on each kidney, is there any hope? National Kidney Foundation. May 2013.

• Simple kidney cysts. National Kidney Foundation. February 2017.

• Renal cysts. Radiological Society of North America. February 2019.

• Kidney cysts and polycystic kidney disease. Urology Austin. 

• What is kidney cancer? Urology Care Foundation. 

Disclaimer

Member comments are lightly edited for length and to remove identifying information but are otherwise reproduced as they appear in the community as part of public posts.

This content is for general informational purposes only and does not necessarily reflect the views and opinions of any organization or individual. The content should not be used as a substitute for professional medical advice, diagnosis, or treatment. Please consult your healthcare provider about any questions you may have regarding a medical condition.