Wilms' Tumor

Wilms' tumor is a type of childhood cancer that occurs in the kidneys. The kidneys are a pair of kidney bean-shaped organs, located above the waist on either side of the spine, that filter and clean blood and produce urine.

Wilms' tumor also is called nephroblastoma, for nephro, meaning kidney, blast, meaning primitive cell and oma, meaning tumor. It is the fifth most common childhood cancer and one of the most common tumors of the abdomen in children. About 400 children in the United States are diagnosed with Wilms' tumor each year. The disease, which affects boys and girls equally, can occur at any age between infancy and 15 years, although it's usually diagnosed by age 3.

Typically it occurs in one kidney but occasionally involves both. If the cancer spreads, it usually spreads to the lungs and liver. With treatment, many children can have a good prognosis for recovery.

Generally, the condition causes a painless swelling in the abdomen and is discovered while bathing, dressing or changing the diapers of your child. Some children may have bloody urine, abdominal pain, loss of appetite, fatigue or weight loss.

If a tumor is suspected in your child's abdomen, don't apply pressure to this area. Careful bathing and handling of your child is important before and during any tumor evaluation. If the tumor ruptures, cancer cells could spread to other tissues of the body.

Children with Wilms' tumor may experience many different symptoms. The following, however, are the most common:

  • Mass or lump, which causes no tenderness, in the abdomen
  • Pain in the abdomen from pressure on other organs near the tumor
  • Swelling of the abdomen
  • Veins that appear distended or large across the abdomen
  • Blood in the urine
  • Decreased appetite
  • Fever
  • High blood pressure
  • Weakness or tiredness

Your child's doctor will conduct a complete medical history and physical examination. Diagnostic procedures may include:

  • Abdominal Computed Tomography (CT or CAT) Scan — This is a diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce cross-sectional images, both horizontally and vertically, of the body. These images, often called slices, are more detailed than X-rays. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat and organs.

  • Abdominal Ultrasound — This is a diagnostic imaging technique that uses high-frequency sound waves and a computer to create images of blood vessels, tissues and organs. It can provide an outline of the kidneys and tumor as well as identify problems in the renal or other major veins in the abdomen. It also can determine if there are any lesions or tumors in a kidney.

  • Show More

Surgery, chemotherapy and radiation therapy are common treatments for Wilms' Tumor, depending on the stage of the cancer and the condition of your child.


Surgery is a common treatment for Wilms' tumor. Your child's doctor may take out the cancer using one of the following:

  • Partial Nephrectomy — This procedure removes the cancer and part of the kidney around the cancer. It typically is used only in special cases, such as when the other kidney is damaged or has already been removed.

  • Simple Nephrectomy — This procedure removes an entire kidney. The other kidney can take over filtering blood.

  • Radical Nephrectomy — Radical nephrectomy is performed to remove an entire kidney as well as tissues around it. Some lymph nodes also may be removed.

Show More

UCSF Research & Clinical Trials

Other Resources


Reviewed by health care specialists at UCSF Benioff Children's Hospital.

Related Information

UCSF Clinics & Centers

Cancer & Blood Disease

Oncology Clinic
1825 Fourth St., Sixth Floor
San Francisco, CA 94158
Phone: (415) 476-3831
Fax: (415) 502-4372
Appointment information

Treatment Center
1825 Fourth St., Sixth Floor
San Francisco, CA 94158
Phone: (415) 353-2584
Fax: (415) 353-2600
Appointment information