Health A-Z

Medical Content Created by the Faculty of the Harvard Medical School


What Is It?

The kidneys are a pair of bean-shaped, fist-sized organs below the rib cage in the back of the abdomen. One sits on each side of the spine. They filter waste products, excess water, and salt from the blood. These organs regulate the body's balance of fluids. They also produce hormones that monitor blood pressure and regulate the production of red blood cells.

Patients whose kidneys have failed or don't work well generally need dialysis or a kidney transplant. During dialysis, a machine takes on the job of filtering waste products from the blood.

Kidney cancer occurs when abnormal kidney cells grow and divide uncontrollably. The cells invade and destroy the normal kidney tissue, and they can spread (metastasize) to other organs. Even if a person has kidney cancer, their kidneys may still function normally.

Kidney cancer includes renal cell carcinoma, which has several sub-types, and transitional cell carcinoma. The most common types of renal cell carcinoma are clear cell cancer, papillary cell cancer, and chromophobe renal cell cancer.

Renal cell carcinoma accounts for most kidney cancers. It begins in the lining of the small tubes that make up the kidney. Although renal cell carcinoma typically develops as a single tumor in one kidney, it sometimes affects more than one part of a kidney or even both kidneys. It has been linked to smoking and exposure to cadmium.

Certain genetic abnormalities can cause renal cell carcinoma or make people more likely to develop it. In these cases, the cancer generally starts at an early age and may affect both kidneys. For example, people with von Hippel-Lindau disease are prone to developing kidney cancer.

Transitional cell carcinoma accounts for only a small percentage of kidney cancers. It usually begins in the renal pelvis. This funnel-shaped structure, which connects the ureter to the main part of the kidney, drains urine from the kidney. Transitional cell carcinoma can also affect the ureters, which carry urine from the kidneys to the bladder, and the bladder lining. Studies suggest that this type of cancer is also linked to smoking.

Most kidney cancers in children develop before age 5. They are commonly called Wilms' tumors.

You risk of kidney cancer is higher if kidney cancer runs in your family or if you

  • smoke

  • are obese

  • have had prolonged exposure to asbestos, cadmium, or petroleum products

  • have family members who have had kidney cancer

  • have had long-term dialysis treatment

  • are between ages 50 and 70

  • have tuberous sclerosis, a disease characterized by bumps on the skin caused by small tumors in blood vessels

  • have von Hippel-Lindau disease, a rare genetic disorder that causes tumors to grow in various parts of the body.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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