Wilms tumor is a type of kidney cancer that occurs in children.

Wilms tumor is the most common form of childhood kidney cancer. The exact cause of this tumor in most children is unknown.

A missing iris of the eye (aniridia) is a birth defect that is sometimes associated with Wilms tumor. Other birth defects linked to this type of kidney cancer include certain urinary tract problems and enlargement of one side of the body, a condition called hemihypertrophy.

It is more common among some siblings and twins, which suggests a possible genetic cause.

The disease occurs in about 1 out of 200,000 to 250,000 children. It usually strikes when a child is about 3 years old. It rarely develops after age 8.

• Abdominal pain
• Constipation
• Fever
• General discomfort or uneasiness (malaise)
• High blood pressure
• Increased growth on only one side of the body
• Loss of appetite
• Nausea
• Swelling in the abdomen (abdominal hernia or mass)
• Vomiting

Note: Abnormal urine color may also be associated with this disease.

Special emphasis is placed on the history and physical exam. The doctor ask if you have a family history of cancer and look for associated birth defects in the child.

A physical examination reveals an abdominal mass. High blood pressure may also be present.

Blood in the urine occurs in less than 25% of children.

Tests include:

• Abdominal ultrasound
• Abdominal x-ray
• BUN
• Chest x-ray
• Complete blood count (may show anemia)
• Creatinine
• Creatinine clearance
• CT scan of the abdomen
• Intravenous pyelogram
• Urinalysis

Other tests may be required to determine if the tumor has spread.

If your child is diagnosed with this condition, avoid prodding or pushing on the child's belly area, and use care during bathing and handling to avoid injury to the tumor site.

The first step in treatment is to stage the tumor. Staging helps doctors determine how far the cancer has spread and to plan for the best treatment. Surgery to remove the tumor is scheduled as soon as possible. Surrounding tissues and organs may also need to be removed if the tumor has spread.

Radiation therapy and chemotherapy will often be started after surgery, depending on the stage of the tumor.

Children whose tumor has not spread have a 90% cure rate with appropriate treatment.

The tumor may become quite large, but usually remains self-enclosed. Spread of the tumor to the lungs, liver, bone, or brain is the most worrisome complication.

High blood pressure and kidney damage may occur as the result of the tumor or its treatment.

Removal of Wilms tumor from both kidneys may affect kidney function.

Call your health care provider if you discover an lump in your child's abdomen, blood in the urine, or other symptoms of Wilms tumor.

Call your health care provider if your child is being treated for this condition and symptoms get worse or new symptoms develop, particularly cough, chest pain, weight loss, or persistent fevers.

For children with a known high risk of Wilms tumor, screening with ultrasound of the kidneys may be recommended.

Kim S. Surg Clin North Am. April 2006; 86(2): 469-87, xi.

Jaffe N, Huff V. Neoplasms of the KidneyIn: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:Chap. 499.