The kidneys are paired organs which are located toward the back of the body, beneath the rib cage. Their primary function is to filter the blood which circulates throughout the body and to excrete the waste products in the urine. The kidneys are composed of millions of microscopic tubules which comprise filtering units. As they filter the blood, urine accumulates and exits the kidneys via the ureters, which carry the urine to the bladder. Urine is stored in the bladder until it is expelled from the body.
Kidney cancer affects some 36,160 people in the United States each year, and close to 12,660 die from the disease. It is the eighth most common cancer in men and the tenth most common in women. Cancerous, or malignant, cells are abnormal cells which grow at an incredibly fast rate, coalesce, and form a mass, or a tumor. Once these cells connect together to form a tumor they do not stop growing. Rather, tumors can grow uncontrollably and eventually even spread beyond the area where they first began growing. Little pieces of tumor can also break off and spread to distant places in the body, via the blood system or the lymphatic system. This is called metastasis. Therefore, it is important to catch cancers before they grow too large and spread to distant sites.
The most common type of kidney cancer — renal-cell carcinoma — accounts for 85% of kidney tumors and occurs twice as often in men as in women. It is most frequently diagnosed in people between the ages of 50 and 70. There are other types of cancer, including transitional-cell carcinoma and sarcoma.
Kidney cancer is usually not suspected until the patient begins to experience symptoms; at this point the tumor may have grown fairly large. In fact, the majority of kidney tumors are now diagnosed incidentally when diagnosing another illness. Symptoms of kidney cancer include: blood in the urine, low back pain that cannot be accounted for by something else (such as an injury), a mass or lump in the abdomen, fatigue, unexplained weight loss, which may be rapid, or fever that is not due to a cold or flu. Unfortunately, many of these symptoms occur with many other types of conditions and are often overlooked.
Currently, all the causes of kidney cancer are not known, but there are several well-described risk factors. These include: smoking, which doubles the risk of kidney cancer, long-term dialysis, exposure to asbestos, such as occupational exposure, exposure to cadmium, a metal which can increase the cancer-causing effect of smoking, a family history of kidney cancer, von Hippel-Lindau syndrome, and tuberous sclerosis, a disease characterized by several bumps on the skin, seizures, mental retardation, and cysts in certain internal organs. Some studies suggest that being overweight and eating a diet high in fat may increase the risk of kidney cancer.
Although there is no sure way to prevent kidney cancer, one can clearly reduce the risk by not smoking or by quitting, if one does smoke.