The role of the kidneys

The kidneys are bean-shaped organs located below the ribcage near the middle of your back. Most people have two kidneys, each about the size of a fist, one on each side of the spine. Each kidney is made up of two distinct sections.

The kidneys have four main functions in the body:

• To maintain fluid balance
• To remove waste products
• To control blood pressure
• To produce hormones needed to make blood and to maintain strong bones (Hormones are chemical messengers that stimulate or control the activity of cells or organs.)

Blood passes through the kidneys to be cleaned before returning to the heart. Blood enters the kidneys through two vessels called renal arteries. Within the kidney are millions of tiny structures called nephrons. The nephrons are the actual filters that remove the waste products and fluid from the blood.

The kidneys also produce urine, which is made up of excess water and waste products filtered from the blood. The urine travels to the bladder (a balloon-shaped storage pouch) through two tubes called ureters. The bladder empties urine from the body (urination) through another tube called the urethra.

The kidneys regulate blood pressure by controlling how much water is in the blood (blood volume). More blood volume means the heart has more fluid to pump and there is more force against the walls of the blood vessels, which results in higher blood pressure. The kidneys control blood volume by secreting a special hormone and by changing the balance of certain chemicals – including potassium and sodium – in the blood.

The kidneys also produce several important hormones, including:

• Erythropoeitin — This hormone triggers the bone marrow (the soft, spongy tissue inside the large bones of the body where blood cells are formed) to make red blood cells. Red blood cells carry oxygen to the body’s cells.
• Renin —This hormone regulates blood pressure.
• Calcitriol —This hormone tells the intestines to absorb calcium from the foods we eat. Calcium is a mineral that helps maintain healthy bones and teeth.

What is kidney cancer?

Kidney cancer is the abnormal growth of cells in kidney tissue. In time, these cells form a mass called a tumor. Cancer begins when something triggers a change in the cells, and they divide out of control. A cancerous, or malignant, tumor can metastasize, or spread, to other tissues and vital organs.

There are different types of kidney cancer, including:

• Renal cell carcinoma (RCC) — This is the most common form of kidney cancer in adults and accounts for 85% of all kidney cancers. Renal cell carcinoma usually develops as a single tumor in one kidney, but it can affect both kidneys. Renal cell carcinoma begins in the cells that line the small tubes that are part of the nephrons within the kidneys. (Renal is the Latin word for kidney, and the term "carcinoma" refers to cancer that begins in the cells that line or cover an organ.)
• Transitional cell carcinoma — Transitional cell carcinoma accounts for 6% to 7% of all kidney cancers. This cancer usually begins in the area where the ureter connects to the main part of the kidney. This area is called the renal pelvis. Transitional cell carcinoma also can occur in the ureters or bladder.
• Renal sarcoma — This is the least common form of kidney cancer, accounting for only 1% of kidney cancer cases. It begins in the connective tissues of the kidneys and, if not treated, can spread to nearby organs and bones.
• Wilms’ tumor — This is the most common type of kidney cancer in children. It accounts for about 5% of kidney cancers.

The information in this document refers to renal cell carcinoma.

What are the symptoms of kidney cancer?

Kidney cancer may not produce any noticeable symptoms in its early stages. However, as the tumor grows, symptoms may begin to appear. For that reason, kidney cancer is often not diagnosed until it has begun to spread.

Symptoms of kidney cancer can include:

• Blood in the urine (a condition called hematuria)
• A lump or mass in the kidney area
• Tiredness
• Loss of appetite and/or weight
• Low-grade fever
• Pain in the side
• Bone pain
• A general sense of not feeling well
• High blood pressure
• Anemia (a condition that results from not having enough red blood cells)

What causes kidney cancer?

The exact cause of kidney cancer is not known, but several risk factors have been identified. A risk factor is something -- such as a characteristic or behavior -- that increases your chance of developing a disease. Risk factors for kidney cancer include:

• Smoking — Smokers are at greater risk for kidney cancer. In addition, the longer a person smokes, the higher the risk.
• Radiation — Women who have been treated with radiation for cancer of the reproductive organs may have a slightly increased risk for developing kidney cancer.
• Gene changes (mutations) — Genes contain instructions for a cell’s function. Changes in certain genes can increase the risk of developing kidney cancer.
• Family history — People who have family members with kidney cancer may have an increased risk for developing the cancer themselves.
• History of tuberous sclerosis — Tuberous sclerosis is a disease that causes seizures and mental retardation, as well as the formation of tumors in many different organs.
• Long-term dialysis treatment — Dialysis is the process of cleaning the blood by passing it through a special machine. Dialysis is used when a person’s kidneys are not functioning properly.
• Von Hippel-Lindau (VHL) disease — People with this inherited disorder are at greater risk for developing kidney cancer. This disorder causes non-cancerous tumors in the blood vessels, typically in the eyes and brain.

How common is kidney cancer?

Kidney cancer represents about 3 percent of all cancers in the United States. Each year, more than 28,000 Americans are diagnosed with kidney cancer. The risk of kidney cancer increases with age. It is more common in men than in women.

How is kidney cancer diagnosed?

If you have symptoms, your doctor will perform a complete medical history and physical examination. The doctor also may order certain tests that can help in diagnosing and assessing cancer. These tests can include:

• Urine tests — A sample of urine is tested to see if it contains blood. Even very small traces of blood, invisible to the naked eye, can be detected in tests of urine samples.
• Blood tests — These tests are done to count the number of each of the different kinds of blood cells. A blood test can show if there are too few red blood cells (anemia).
• Intravenous pyelogram (IVP) — This is a special type of X-ray. During an IVP, a special dye containing iodine is given through a needle inserted into a vein, and a series of X-rays are taken. The dye travels through the bloodstream and eventually into the kidneys, making the kidneys easier to see on the X-rays.
• Computed tomography (CT or CAT) scan — This is a special X-ray that uses a computer to create a series of images, or slices, of the inside of the body.
• Magnetic resonance imaging (MRI) — This is a test that produces images of the inside of the body using a large magnet, radio waves and a computer.
• Ultrasound — This test uses high-frequency sound waves that are transmitted through body tissues to create images that are displayed on a monitor. This test is helpful in detecting tumors, which have a different density than healthy tissues.
• Arteriogram — This is a series of X-rays of the blood vessels taken after a contrast solution is injected to make the blood vessels more visible.
• Fine needle aspiration biopsy — During this procedure, a thin needle is inserted into the tumor, and a small sample of the tissue is removed (biopsy). The doctor will look at the tissue under the microscope to see if there are any cancer cells.

Most cancers are grouped by stage, a description of the cancer that aids in planning treatment. The stage of a cancer is based on the location and size of the tumor; the involvement, if any, of the lymph nodes; and the degree that the cancer has spread, if at all, to other tissue and organs. The doctor uses information from various tests -- such as CT, MRI and biopsy -- to determine the stage of the cancer.

Stages of kidney cancer

• Stage I — The tumor is confined to the renal capsule (the fibrous tissue surrounding the kidney) and is smaller than ¾ inch in length or larger than ¾ inch but has not spread to lymph nodes or other tissue. (Lymph nodes are small "filters" that trap germs and cancer cells, and store infection-fighting cells.)
• Stage II — The tumor has spread to the surrounding fat and adrenal gland (small gland that sits on top of the kidney.)
• Stage III — The tumor has spread to the major blood vessels – the renal vein and inferior vena cava -- and regional lymph nodes.
• Stage IV — The cancer has spread to nearby organs or lymph nodes, or to distant organs.

Tumors are also graded, which is a way of rating a tumor based on how abnormal its cells look. Tumor grading can also tell the doctor how fast the tumor is likely to grow. Tumors whose cells do not look like normal cells and divide rapidly are called high-grade tumors. High-grade tumors tend to grow and spread more quickly than low-grade tumors.

How is kidney cancer treated?

Treatment depends on the type of cancer, the stage and grade of the tumor, and the patient's age and overall health.

Surgery is the most common treatment for kidney cancer. Several surgical options may be considered, including:

• Simple nephrectomy — The surgeon removes just the kidney.
• Partial nephrectomy — The surgeon removes just the part of the kidney that contains the tumor.
• Radical nephrectomy — The surgeon removes the whole kidney, along with the adrenal gland and some of the tissue around the kidney. Some lymph nodes in the area also may be removed.

When one kidney is removed, the remaining kidney usually is able to perform the work of both kidneys.

A procedure called arterial embolization is sometimes used before surgery. During this procedure, a small catheter (tube) is inserted into an artery in the groin and moved through the blood vessel until it reaches the kidney. A special material is injected through the catheter to block the main blood vessel of the kidney (renal artery). This prevents the cancer cells from getting oxygen or other substances they need to grow.

Surgery is the treatment of choice for most stages of kidney cancer. Chemotherapy or biological therapy may be used for stage IV cancer, when the cancer has spread beyond the kidney. Chemotherapy, or chemo, uses medicines to kill or stop the growth of cancer cells. Biological therapy uses the body’s own immune system to fight cancer.

Hormone therapy is another treatment option. This treatment uses hormones to try and control the growth of cancer cells.

Some people with kidney cancer participate in clinical trials. Clinical trials are research programs conducted with patients to evaluate new medical treatments, drugs or devices. Clinical trials also are being conducted on new chemotherapy drugs and on new ways to use biological therapy for patients with kidney cancer.

What is the outlook for people with kidney cancer?

The chance of recovery depends on the type and stage of the cancer (whether it is just in the kidney or has spread to other places in the body), as well as the patient's general state of health.

Like most cancers, the chance of treatment success is highest if kidney cancer is found in its early stages. In general, if the cancer is detected early, before it breaks through the outer covering of the kidney, the kidney cancer is often curable.

Can kidney cancer be prevented?

Because the exact cause of kidney cancer is not known, there is no known prevention. However, you may be able to reduce your risk by quitting smoking, and avoiding exposure to asbestos and cadmium.