Kidney cancer occurs when cells in the kidney divide without control or order, forming a growth called a tumor and sometimes spreading to other parts of the body.
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Renal cell carcinoma
The kidneys are two bean-shaped organs located near the spine whose main function is to filter salts, excess water, and impurities from the blood, producing the liquid waste called urine. Urine drains from the kidneys to the bladder through a tube called the ureter. It is stored in the bladder until it leaves the body through another tube called the urethra. The kidneys also help produce red blood cells and help maintain healthy blood pressure.
If cancer develops in the kidneys, it may affect not only the kidneys but nearby organs as well, including the liver, pancreas, and large intestine. Or kidney cancer cells may spread through the bloodstream or lymphatic system to other parts of the body. The most common form of kidney cancer in children is Wilms' tumor, and the most common form of kidney cancer in adults is renal cell cancer.
Wilms' tumor, the most common cause of kidney cancer in children, begins to develop even before a child is born. As the fetus grows in the womb, the kidney cells develop into the netlike structures of blood ves-sels and tissues that are needed to filter the blood. When these cells do not mature as they should, the baby is born with some underdeveloped cells. Usually these cells mature by the time a child is three or four. But sometimes they start to grow out of control, forming the jumbled mixture of small cells called a Wilms' tumor, after the German doctor Max Wilms (1867-1918), who first wrote about it in 1899.
* chemotherapy (kee-mo-THER-a-pee) is the treatment of cancer with powerful drugs that kill cancer cells.
Doctors find the tumor when a mass is felt while examining a baby's belly. There are usually few, if any, symptoms. If the tumor has not spread out of the kidney, the outlook for the child's recovery is excellent. Most children with Wilms' tumor are treated with surgery or chemo-therapy. * If the cancer has spread beyond the kidney, doctors might also prescribe radiation therapy, which uses focused, high-energy rays to destroy cancer cells.
Adult Kidney Cancer
Kidney cancer in adults is much more common than in children, affecting about 30,000 people each year. In four out of five cases, the tumor forms in the tissue responsible for filtering the blood, but it also can affect the renal pelvis, the structure that collects the urine after filtration. Unlike Wilms' tumor, kidney cancer in adults often spreads to nearby organs and to other parts of the body.
Kidney cancer is more common in people who smoke cigarettes. Exposure to certain harsh chemicals and to medications containing the pain-reliever phenacetin appears to increase risk for the disease. Heredity can play a role too. However, many cases of kidney cancer develop without apparent cause. The most common early symptoms include:
- Blood in the urine.
- Pain in the lower back.
- Unexplained weight loss.
- Recurring fevers.
- High blood pressure.
How Do Doctors Diagnose and Treat Kidney Cancer?
Doctors start with a medical history, physical examinastion, and laboratory tests of blood and urine samples. Based on their findings, they may order tests that produce pictures of the kidneys and nearby organs. Additional tests may be ordered, including:
- Intravenous pyelogram (IVP) (in-tra-VEN-us PY-e-lo-gram), which is a series of x-rays of the kidneys, ureters, and bladder after dye is injected.
- Arteriogram (ar-TER-ee-o-gram), which is a similar test that creates images of the network of blood vessels in and around the kidney.
- Imaging tests, such as CT scans * , MRls * , and ultrasound * .
If kidney cancer is suspected, a surgeon will perform a biopsy by inserting a thin needle into the tumor and removing a sample of tissue to be examined under the microscope. If these cells turn out to be cancerous, doctors need to find out whether or not the cancer has spread beyond the kidney. Kidney cancer cells often spread through the bloodstream or the lymph nodes, which filter the infection-fighting fluid called lymph. Doctors may order more imaging tests to examine nearby organs and to check for swollen lymph nodes in the chest and abdomen. They also may order chest x-rays and bone scans, because the cancer most often spreads to the lungs or the bones. If the cancer is found to have spread to the lungs or other organs, it still will be kidney cancer because those are the cancer cells that have spread.
* CT scans or CAT scans are the shortened names for computerized axial tomography (to-MOG-ra-fee), which uses computers to view structures inside the body.
* MRI, which is short for magnetic resonance imaging, produces computerized images of internal body tissues based on the magnetic properties of atoms within the body.
* ultrasound is a painless procedure in which sound waves passing through the body create images on a computer screen.
How the disease is treated depends on whether it has spread beyond the kidney. If it has not, the most common treatments are surgery and radiation therapy. Surgery involves removing part or all of the kidney, a procedure called nephrectomy (nef-REK-tom-ee). The remaining kidney generally is able to perform the work of both kidneys.
Kidney cancer that has spread to other parts of the body is very difficult to treat. Doctors can use biological therapy, chemotherapy, and hormone therapy. Biological therapy, also called immunotherapy, attempts to boost the body's own natural defenses against the cancer. Interleukin-2 and interferon are two examples of substances that are used as "immune boosters." Chemotherapy delivers anti-cancer drugs into the person's bloodstream through a needle or in pill form. Hormone therapy involves blocking or increasing the body's own chemical messengers (hormones) to try to control the growth of cancer cells.
These treatments have helped only a small percentage of people with advanced kidney cancer. That is why researchers are conducting clinical trials, which are research studies with volunteer patients, to test new treatment approaches. People with advanced kidney cancer and their caregivers also find support groups a valuable resource.
U.S. National Cancer Institute, National Institutes of Health, Bethesda,
MD. NCI posts a fact sheet called
What You Need to Know about Kidney Cancer
at its website. Its CancerTrials website posts information about
U.S. National Kidney and Urologic Diseases Information Clearinghouse, 3
Information Way, Bethesda, MD 20892-3580. This division of the National
Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) posts
many different fact sheets about the kidney at its website.
American Cancer Society Cancer Resource Center. The ACS posts
information about Wilms' tumor and adult kidney cancer at its
Kidney Cancer Association, 1234 Sherman Avenue, Suite 203, Evanston, IL