Many people have cysts on the kidney. While most kidney cysts are benign, some may be cancerous.
Kidney cysts, also known as renal cysts, are relatively common fluid-filled growths that a person may be born with or develop with age. Cysts are found in as many as
Many cysts are benign, meaning they’re not cancerous and don’t require any treatment. Some cysts, though, may be malignant, meaning they’re cancerous.
Keep reading to learn more about what kidney cysts are, how they’re diagnosed, and whether they lead to kidney cancer.
The kidneys are bean-shaped organs found on the right and left sides of the middle back, behind the abdomen. They remove water, salt, and other waste from the blood and turn it into urine that travels to the bladder to later be expelled from the body during urination.
Kidney cysts are fluid-filled sacs that are found on the surface of one or both of the kidneys. There are two types of cysts:
- Simple cysts: These are single cysts that have a thin wall around them and are filled with watery fluid.
- Complex cysts: These have thicker walls and may have fluid and other solid matter inside them.
Cysts can be large or small. And a person can have one cyst or many on one or both kidneys, though they’re more
When cysts do cause symptoms, a person may experience abdominal pain or trouble with urination. However,
Kidney cancer is a cancer (malignant growth) that begins in the kidneys. This type of cancer affects over
Tumors are made up of things like fat, muscle, connective tissue, and other matter that form a mass on the organ. Over time, tumors may continue to grow and spread to other parts of the body.
There are various types of kidney cancer, including:
- Renal cell carcinoma: This type can be divided into clear cell renal cell carcinoma and nonclear cell renal cell carcinoma. It makes up about
9 out of every 10cases of kidney cancer. It may be made up of just onetumor, or two or more.
- Transitional cell carcinoma: This cancer begins in the renal pelvis and makes up between
5 and 10of every 100 cases of kidney cancer.
- Nephroblastoma: Also called Wilms’ tumor, this type of cancer primarily affects children and is
- Renal sarcoma: This
rarekidney cancer begins in the connective tissue and blood vessels of the kidney.
People may also develop noncancerous tumors on the kidneys called angiomyolipomas or oncocytomas. Unlike cysts, they’re masses and aren’t filled with fluid. And, unlike cancer, they don’t spread to other parts of the body.
Cysts are classified according to a system called the Bosniak classification scale. The rating system takes into account the size of the cyst and other features, like the composition (fluid versus tissue, etc.).
Simple kidney cysts — the most
Complex cysts, on the other hand, may be malignant.
Bosniak classification scale for cysts
|Bosniak I cyst||< 1%|
|Bosniak II cyst||< 1%|
|Bosniak IIF cyst||5%|
|Bosniak III cyst||55%|
|Bosniak IV cyst||100%|
The main difference between kidney cysts and kidney cancer is the makeup of the cyst itself. Simple cysts — those that don’t typically lead to cancer — are filled with watery fluid and have thin walls. Complex cysts — those that may lead to cancer — are thicker and filled with fluid and tissue.
Cysts that are benign won’t spread to other parts of the body. Cancer that’s not treated, on the other hand, can start in the kidneys, grow, and then spread to nearby organs and eventually to the rest of the body.
Cysts may be diagnosed through imaging tests, such as ultrasound, computerized tomography (CT) scan, or magnetic resonance imaging (MRI). These tests allow doctors to see the difference between cysts, tumors, and other issues.
Diagnosing kidney cancer also involves imaging tests and laboratory tests.
- Urine test: These tests check for blood in the urine or, in some cases, cancer itself.
- Complete blood count (CBC): Complete blood count (CBC) checks for anemia (low red blood cell count) or polycythemia (high red blood cell count).
- Blood chemistry test: These tests evaluate liver enzymes, calcium levels, and other chemical levels.
Your doctor may also order a renal biopsy to confirm other results. A biopsy involves taking a sample of tissue from the kidney and examining it in a lab. The procedure may be performed via fine needle aspiration (FNA) or core needle biopsy.
The risk for developing kidney cysts increases with age. They’re more common in people over
Risk factors for kidney cancer are similar. Again, kidney cancer tends to be more
Additional risk factors for cancer are:
- Race: African Americans have a
slightlyhigher risk than other groups.
- Weight: Cancer is more
commonin people who have obesity due to certain hormonal changes.
- Medications: Taking the pain reliever acetaminophen may play a role.
- Chemical exposure: A chemical called trichloroethylene, a degreasing solvent, has also been linked to kidney cancers.
Cysts that are rated I to IIF on the Bosniak scale aren’t likely to be cancer. Your doctor may or may not order additional follow-up testing or treatment because they’re likely benign and don’t pose a threat to your health. Cysts that are rated III or IV have a much
The outlook for kidney cancer depends on the specific type of cancer a person has. That said, the
- Localized: Kidney cancer is only in the kidney itself; the 5-year survival rate for localized cancers is
- Regional: Cancer has spread to lymph nodes or nearby tissue; the 5-year survival rate for regional cancers is
- Distant: Cancer has spread to other organs, like the brain, lungs, or bones; the 5-year survival rate for distant cancers is
Overall, the 5-year survival rate for kidney cancer is
How long do kidney cysts last? Do they ever go away on their own?
There’s no set amount of time that a cyst may stay on the kidney. Simple cysts may go away on their own or last for years without causing symptoms. If they’re not causing symptoms/damage and aren’t cancerous, it’s OK for them to remain on the kidney.
What treatments are available for kidney cysts?
Bosniak I, II, and IIF cysts don’t require any treatment, like drainage, unless they cause symptoms. Your doctor may suggest a biopsy and surgery for Bosniak III and IV cysts.
Can I prevent cysts on the kidneys?
Kidney cysts don’t always cause symptoms and may be discovered by chance via imaging for some other health issue.
Simple kidney cysts are rarely cancerous and most often don’t require any treatment unless they’re symptomatic. Complex cysts that are a level III and IV on the Bosniak scale should be monitored and treated to prevent kidney damage and any possible cancer from spreading.