Health Library

Wilms' Tumor


Wilms' tumor is a type of kidney cancer that mainly affects children. In most cases, Wilms' tumor affects only 1 of the 2 kidneys.

The Kidneys
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In the fetus, some of the cells that are supposed to grow into mature kidneys stay as fetal kidney cells. Clusters of these cells sometimes remain after birth. If they do not mature within 3 or 4 years, they may grow without control or order. A large mass of these cells may develop into a Wilms' tumor.

Risk Factors

A small percentage of children with Wilms' tumors have inherited an abnormal gene from one parent. This gene increases the chance that kidney cells will turn into a Wilms' tumor. Having a family member with a Wilms' tumor also increases the risk in a child.

Also, certain birth defects increase the risk of a Wilms' tumor. These include:

  • WAGR—a syndrome that includes:
    • W ilms' tumor
    • A niridia—completely or partly missing the colored part of the eyes called the iris
    • G enitourinary abnormalities—defects of the kidneys, urinary tract, penis, scrotum, testicles, clitoris, or ovaries
    • Mental R etardation
  • Beckwith-Wiedemann syndrome—larger than normal tongue and internal organs; 1 arm or leg may be larger than the other
  • Perlman syndrome—large fetal size, renal dysplasia, Wilms' tumor, islet cell hypertrophy, multiple congenital anomalies, and mental retardation
  • Denys-Drash syndrome—absence of the penis, scrotum, and testicles
  • Hemihypertrophy—1 side of the body larger is than the other
  • Other genetic defects, including defects on chromosome 11.

Many children with Wilms' tumors do not have any known inherited gene changes or birth defects. It is not known why these children have some kidney cells that do not mature properly.


The first noticeable symptom is usually a large lump or hard mass in the abdomen. Other symptoms may include:

  • Stomach pain
  • Fever
  • Blood in the urine
  • Loss of appetite, nausea, vomiting, and constipation

Wilms' tumors may grow larger without causing any pain or other symptoms.


You will be asked about your child’s symptoms and medical history. A physical exam will be done.

Your child's bodily fluids and tissues may be tested. This can be done with:

  • Blood tests
  • Urine tests
  • Biopsy

Images may be taken of your child's bodily structures. This can be done with:

Children who have risk factors for Wilms' tumor should have a physical exam with a specialist and an ultrasound every 3 months until age 6 or 7. This screening should be done even if they do not have symptoms. It can help find tumors while they are small and have not yet spread to other parts of the body.


Wilms' tumor can be cured in most children. The specific treatment depends on whether the cancer has spread beyond the kidney to other parts of the body. The process for determining this is called staging. It uses the results of the diagnostic tests. Tumor size, cell type, tumor type, and your child’s age and health are also considered in choosing treatment.

In general, most tumors are treated only with combinations of chemotherapy. Other tumors often require the addition of radiation therapy.

Treatment may include:


The main treatment for Wilms' tumor is a type of surgery called nephrectomy. This is the removal of the kidney with the tumor. The tissue around the kidney may also be removed, as well as some nearby lymph nodes. The remaining kidney will take care of all of the needed functions for the body.


Chemotherapy is the use of drugs to kill cancer cells. Chemotherapy can be given in many forms, including pill, injection, and through a tube called a catheter. The drugs enter the bloodstream and travel through the body destroying mostly cancer cells, but also some healthy cells.

Radiation Therapy

This is the use of radiation to kill cancer cells and shrink tumors. External radiation therapy may be directed at the tumor from a source outside the body.

Radiation of Tumor
Radiation of Tumor
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There are no current guidelines to prevent Wilms' tumor.


American Cancer Society

National Cancer Institute

Canadian Resources

Childhood Cancer Canada

Sick Kids—The Hospital for Sick Children


Driskoll K, Isakoff M, Ferrer F. Update on pediatric genitourinary oncology. Curr Opin Urol. 2007;17(4):281-286.

Wilms tumor. EBSCO DynaMed Plus website. Available at: Updated October 8, 2015. Accessed September 6, 2016.

Wilms tumor. Kids Health—Nemours Foundation website. Available at: Updated March 2012. Accessed September 6, 2016.