Kidney Cancer Health Article

Definition

Kidney cancer is a disease in which the cells in certain tissues of the kidney start to grow uncontrollably and form tumors. Renal cell carcinoma, sometimes referred to as hypernephroma, occurs in the cells lining the kidneys (epithelial cells). It is the most common type of kidney cancer. Eighty-five percent of all kidney tumors are renal cell carcinomas. Wilms' tumor is a rapidly developing cancer of the kidney most often found in children under four years of age.

Description

The kidneys are a pair of organs shaped like kidney beans that lie on either side of the spine just above the waist. Inside each kidney are tiny tubes (tubules) that filter and clean the blood, taking out the waste products and making urine. The urine that is made by the kidney passes through a tube called the ureter into the bladder. Urine is held in the bladder until it is discharged from the body. Renal cell carcinoma (RCC) generally develops in the lining of the tubules that filter and clean the blood. Cancer that develops in the central portion of the kidney (where the urine is collected and drained into the ureters) is known as transitional cell carcinoma of the renal pelvis. Transitional cell cancer is similar to bladder cancer. Wilms' tumor is the most common type of childhood kidney cancer and is distinct from kidney cancer in adults.

Demographics

Kidney cancer accounts for approximately 3% of all cancers. In the United States, kidney cancer is the tenth most common cancer and the incidence has increased by 43% since 1973; the death rate has increased by 16%. There are approximately 20, 000 new cases of kidney cancer found each year. There are approximately 95, 000 deaths per year worldwide due to kidney cancer. RCC accounts for 90-95% of malignant neoplasms that originate from the kidney.

Kidney cancer occurs most often in men over the age of 40. The median age of diagnosis is 65. Men are twice as likely as women are to have cancer of the kidney.

Causes and symptoms

The causes of kidney cancer are unknown, but there are many risk factors associated with kidney cancer. The risk factors listed from greatest to smallest include:

• von Hippel-Lindau disease (> 100)

• Chronic dialysis (32)
• Obesity (3.6)
• Tobacco use (cigarettes) (2.3)
• First-degree relative with kidney cancer (1.6)
• Hypertension (1.4)
• Dry-cleaning worker (1.4)
• Diuretics (non-hypertension use) (1.3)
• Trichloroethylene exposure (1.0)
• Heavy phenacetin use (1.1-6.0)
• Polycystic kidney disease (0.8-2.0)
• Cadmium exposure (1.0-3.9)
• Arsenic exposure (1.6)
• Asbestos (1.1-1.8)

The most common symptom of kidney cancer is blood in the urine (hematuria). Other symptoms include painful urination, pain in the lower back or on the sides, abdominal pain, a lump or hard mass that can be felt in the kidney area, unexplained weight loss, fever, weakness, fatigue, and high blood pressure.

Diagnosis

A diagnostic examination for kidney cancer includes taking a thorough medical history and making a complete physical examination in which the doctor will probe (pal-pate) the abdomen for lumps. Blood tests will be ordered to check for changes in blood chemistry caused by substances released by the tumor. Laboratory tests may show abnormal levels of iron in the blood. Either a low red blood cell count (anemia) or a high red blood cell count (erythrocytosis) may accompany kidney cancer. Occasionally, patients will have high calcium levels.

If the doctor suspects kidney cancer, an intravenous urography (also called pyelogram or IVP) may be ordered. An IVP is an x-ray test in which a dye is injected into a vein in the arm. The dye travels through the body, and when it is concentrated in the urine to be discharged, it outlines the kidneys, ureters, and the urinary bladder. On an x-ray image, the dye will reveal any abnormalities of the urinary tract. The IVP may miss small kidney cancers.

Renal ultrasound is a diagnostic test in which sound waves are used to form an image of the kidneys. Ultrasound is a painless and non-invasive procedure that can be used to detect even very small kidney tumors. Imaging tests such as computed tomography (CT) scans and magnetic resonance imaging (MRI) can be used to evaluate the kidneys and the surrounding organs. These tests are used to check whether the tumor has spread outside the kidney to other organs in the abdomen. If the patient complains of bone pain, a special x ray called a bone scan may be ordered to rule out spread to the bones. A chest x ray may be taken to rule out spread to the lungs.

A kidney biopsy is used to positively confirm the diagnosis of kidney cancer. During this procedure, a small piece of tissue is removed from the tumor and examined under a microscope. The biopsy will give information about the type of tumor, the cells that are involved, and the aggressiveness of the tumor (tumor stage).