Kidney cancer occurs when cells in these organs grow uncontrollably and invade other cells. Kidney cancer represents 2 percent of cancers in the United States, according to the U.S. Centers for Disease Control and Prevention (CDC).

The kidneys are two bean-shaped organs that are located in the upper back portion of the abdomen. The kidneys lies on each side of the spine. The kidneys filter toxins from the bloodstream and eliminate waste products from the body as urine. The kidneys also serve other functions such as maintaining blood pressure, modifying levels of salt and water and producing several vital hormones. People have two kidneys but can function with one. If both kidneys fail or are removed, kidney function can be taken over by dialysis, medical machines that function as artificial kidneys.  

Many types of tumors form in the kidneys, including several noncancerous types. The major types of kidney cancer include renal cell carcinoma and transitional cell carcinoma. These types of carcinomas occur mostly in adults. Children rarely get kidney cancer. When they do, it is usually a type called Wilms tumor.

The causes of kidney cancer are unknown. However, several risk factors are closely associated with developing kidney cancer. They include smoking, obesity, high blood pressure, many years of kidney dialysis and certain hereditary conditions.

There are rarely any symptoms in the early stages of kidney cancer. As the tumor grows, blood in the urine (not always visible to the patient) can be found in a urine test. Weight loss, back pain, fatigue and loss of appetite may be present. Kidney cancer that has spread to other organs and tissues can produce additional symptoms.

Diagnosis of kidney cancer usually involves obtaining a medical history, physical examination, blood testing and urine testing. Imaging tests (e.g., CAT scan, ultrasound) may be used to determine the size and spread of the cancer if the disease is suspected. A biopsy may be taken to diagnose the cancer cell type and the stage of the cancer.

Treatment is most successful when the kidney cancer is detected early and when it can be removed surgically. If the cancer spreads or cannot be completely removed with surgery, chemotherapy and/or radiation therapy may be used, but these are not standard treatment options. Other treatments, such as biological therapy (immunology used to enhance the immune system attack on cancer cells) produce better results.

Kidney cancer can recur after treatment and it may return to the same location or reappear in other sites in the body. Depending on the site of recurrence, surgery may be a treatment option to remove the cancer.