Section 11. Kidney and Urinary Tract Disorders

Chapter 151. Cancers of the Kidney and Urinary Tract

Topics: Introduction | Kidney Cancer | Cancers of the Renal Pelvis and Ureter | Bladder Cancer | Cancer of the Urethra

Kidney Cancer

Kidney cancer accounts for about 2 to 3% of cancers in adults, affecting twice as many men as women. Smokers are about twice as likely to develop kidney cancer as nonsmokers. Other risk factors include exposure to toxic chemicals and obesity. For unknown reasons, between 1975 and 1995, the rate of new kidney cancers rose 2 to 4% per year. People affected are usually between 50 and 70 years of age.

Most solid kidney tumors are cancerous, but fluid-filled tumors (cysts) generally are not. Almost all kidney cancer is renal cell carcinoma. Another kind of kidney cancer, Wilms' tumor, occurs in children (see Section 23, Chapter 283).

Symptoms and Diagnosis

Blood in the urine is the most common first symptom, but the amount of blood may be so small that it can be detected only under a microscope. On the other hand, the urine may be visibly red. The next most common symptoms are pain in the flank (the area between the ribs and hip), fever, and weight loss. Sometimes kidney cancer is first detected when a doctor feels an enlargement or lump in the abdomen, or a cancer may be discovered by chance during evaluation of another problem, such as high blood pressure. If the cancer interferes with the blood supply to part or all of the kidney, an enzyme called renin is released, which leads to an increase in blood pressure.

The red blood cell count may become abnormally high, resulting in secondary polycythemia, because high levels of the hormone erythropoietin (which is produced by the diseased kidney or by the tumor itself) stimulate the bone marrow to increase the production of red blood cells. Conversely, kidney cancer may lead to a drop in the red blood cell count because of bleeding into the urine. Some people develop high levels of calcium in the blood (hypercalcemia).

If doctors suspect kidney cancer, they may use intravenous urography, ultrasound, or computed tomography (CT) to confirm the diagnosis. Magnetic resonance imaging (MRI) may be used to provide more information about whether the cancer has spread into nearby structures, including veins. If a fluid-filled tumor (cyst) is found, fluid may be withdrawn with a needle to determine if the tumor is cancerous.

Treatment

When the cancer has not spread (metastasized) beyond the kidney, surgically removing the affected kidney and lymph nodes provides a reasonable chance of cure. A doctor may remove only the tumor plus a rim of adjacent normal tissue, which spares the remainder of the kidney. Sometimes the entire kidney needs to be removed.

If the cancer has spread into the renal vein or even the large vein that carries blood to the heart (vena cava) but has not spread to distant sites, surgery may still provide a chance for cure. However, kidney cancer has a tendency to spread early, especially to the lungs. Treating the cancer by enhancing the immune system's ability to destroy it causes some cancers to shrink and may prolong survival (see Section 15, Chapter 182). One such treatment, interleukin-2, is used for kidney cancer. Various combinations of interleukin-2, interferon, and other biologic agents and even vaccines developed from cells removed from the kidney cancer are being investigated. Rarely (in less than 1% of people), removing the affected kidney causes tumors elsewhere in the body to shrink. However, the slim possibility that this will occur is not considered sufficient reason to remove a cancerous kidney when the cancer has already spread, unless removal is part of an overall plan that includes traditional anticancer drugs (chemotherapy) or biologic agents.

Distant spread of kidney cancer cannot always be detected when kidney cancer is diagnosed. Therefore, spread of the kidney cancer sometimes becomes apparent after the doctor has surgically removed all of the kidney cancer that could be found; cancer that has spread to new areas is usually unresponsive to traditional chemotherapy. However, treatment with interleukin-2 or interferon may be beneficial, although their effects are modest.

Prognosis

Many factors affect prognosis, but the 5-year survival rate for people with cancer confined to the kidney is 85% or better. If the cancer has spread into the renal vein and the vena cava but has not spread to distant sites, the 5-year survival rate is 35 to 60%. When cancer has spread to distant sites, the 5-year survival rate is no higher than 10%. In some instances, the goal is to focus on pain relief and other means to improve the person's comfort (see Section 1, Chapter 8). As with all terminal illnesses, planning for end-of-life issues, including creating advance directives, is essential (see Section 1, Chapter 8 and Section 1, Chapter 9).