Your kidneys are two bean-shaped organs, each about the size of your fist. They're located behind your abdominal organs, one on each side of your spine. Like other major organs in the body, the kidneys can sometimes develop cancer.
In adults, the most common type of kidney cancer is renal cell carcinoma, which begins in the cells that line the small tubes within your kidneys. Children are more likely to develop a kind of kidney cancer called Wilms' tumor.
Kidney cancer rarely causes signs or symptoms in its early stages. In the later stages, kidney cancer signs and symptoms may include:
- Blood in your urine, which may appear pink, red or cola-colored
- Back pain just below the ribs that doesn't go away
- Weight loss
- Intermittent fever
Your kidneys are part of the urinary system, which removes waste and excess fluid and electrolytes from your blood, controls the production of red blood cells, and regulates your blood pressure. Inside each kidney are more than a million small filtering units called nephrons. As blood circulates through your kidneys, the nephrons filter out waste products as well as unneeded minerals and water. This liquid waste — urine — flows through two narrow tubes (ureters) into your bladder, where it's stored until it's eliminated from your body through another tube, the urethra.
Just what causes kidney cells to become cancerous isn't clear. But researchers have identified certain factors that appear to increase the risk of kidney cancer.
Types of kidney cancer
The most common types of kidney cancer include:
- Renal cell carcinoma. This type of kidney cancer usually begins in the cells that line the small tubes of each nephron. In most cases, renal cell tumors grow as a single mass, but you may have more than one tumor in a kidney or develop tumors in both kidneys.
- Transitional cell carcinoma. This type of kidney cancer develops in the tissue that forms the tubes that connect the kidneys to the bladder. Transitional cell carcinomas can also begin in the ureters themselves or in the bladder.
- Wilms' tumor. Wilms' tumor is a type of kidney cancer that occurs in young children.
A kidney cancer diagnosis typically begins with a complete medical history and a physical exam. Your doctor may also recommend blood and urine tests. If your doctor suspects a problem or if you're at high risk of kidney cancer, you may also have one or more of the following tests to check your kidneys for growths or tumors:
- Ultrasound. An ultrasound uses high-frequency sound waves to generate images of your internal organs, such as your kidneys and bladder, on a computer screen.
- Computerized tomography (CT) or magnetic resonance imaging (MRI) scan. CT scans use computers to create more-detailed images than those produced by conventional X-rays. MRI scans use magnetic fields and radio waves to generate cross-sectional pictures of your body.
- Tissue sample (biopsy). In selected cases, your doctor may recommend a procedure to remove a small sample of cells (biopsy) from a suspicious area of your kidney. During a biopsy, a surgeon uses ultrasound or CT images to guide a long, thin needle into your kidney to remove the cells. The cells are then examined under a microscope to determine whether they are cancer.
Biopsy procedures have risks, such as infection, bleeding and a very small chance that cancer could spread to the area where the needle is inserted. Because surgery is usually the first line treatment for kidney cancer, your doctor may forgo biopsy if he or she believes your tumor is very likely to be cancerous. That way you avoid the additional risks of a biopsy. Kidney biopsy is typically reserved for cases that are most likely to be noncancerous or for people who can't undergo an operation.
Additional tests for transitional cell cancer
Tests and procedures used to diagnose transitional cell kidney cancer may include:
- X-ray imaging of your urinary system (excretory urogram). X-rays of your urinary system may show signs of cancer. Your health care team will inject a dye into a vein in your arm. The dye is processed by your kidneys and your urinary system, and the dye makes it possible to see your urinary system on an X-ray.
- Looking inside your bladder (cystoscopy). Your doctor may use a long, narrow tube called a cystoscope to see the inside of your bladder. The cystoscope, which carries a light source and a special lens, is inserted through your urethra into your bladder. A cystoscope can also be used to extract a small tissue sample (biopsy) from any suspicious areas.
Together, you and your treatment team will discuss all of your kidney cancer treatment options. The best approach for you may depend on a number of factors, including your general health, the kind of kidney cancer you have, whether the cancer has spread and your own preferences for treatment.
Surgery is the initial treatment for the majority of kidney cancers. Surgical procedures used to treat kidney cancer include:
- Removing the affected kidney (nephrectomy). Radical nephrectomy involves the removal of the kidney as well as the adrenal gland that sits atop the kidney, a border of healthy tissue and adjacent lymph nodes. Nephrectomy can be done through an incision, meaning the surgeon makes a large cut in your skin to access your kidney. Or nephrectomy can be done laparoscopically, using small incisions to insert a video camera and tiny surgical tools. The surgeon watches a video monitor in order to perform the nephrectomy.
- Removing the tumor from the kidney (nephron-sparing surgery). During this procedure, the surgeon removes the tumor, rather than the entire kidney. Nephron-sparing surgery may be an option if you have only one kidney or if you have an early-stage kidney cancer.
What type of surgery your doctor recommends will be based on your cancer and its stage, as well as your health and personal preferences. Surgery carries a risk of bleeding and infection.
Treatments when surgery isn't possible
For some people, surgery may be too risky. These people have other options for treating their kidney cancers, including:
- Blocking blood flow to the tumor (embolization). In this procedure, a special material is injected into the main blood vessel leading to the kidney. By clogging this vessel, the tumor is deprived of oxygen and other nutrients. Arterial embolization also may be used before an operation or to relieve pain and bleeding when an operation isn't possible. Side effects may include temporary nausea, vomiting or pain.
- Treatment to freeze cancer cells (cryoablation). Recent studies show cryoablation may be useful for treating kidney tumors that can't be removed through surgery. During cryoablation, one or more special needles (cryoprobes) are inserted through small incisions in your skin and into the tumor. Gas in the needles creates extreme cold that causes the cells around the point of each needle to freeze. Doctors use CT scans to monitor the procedure and to ensure that all of the visible cancer tissue and some of the surrounding healthy tissue is frozen. Another type of gas in the needles creates warmth to thaw the frozen tissue. Then the process is repeated. The cycles of freezing and thawing cause cancer cells to die. You may experience some pain after the procedure. Rare side effects may include bleeding, infection and damage to tissue surrounding the tumor.