Children's Hospital Colorado

Wilms Tumors in Children

What is a Wilms tumor?

A Wilms tumor, also known as nephroblastoma, is a malignant (cancerous) tumor that forms in the kidneys. Tumors that form in or on the kidneys are also known as renal tumors. Wilms tumors can affect both kidneys, but usually only forms in one.

At Children’s Hospital Colorado, our Urologic Tumor Program has extensive experience diagnosing and treating Wilms tumor and other tumors of the kidney in kids.

What causes a Wilms tumor in kids?

There is no strong evidence showing that Wilms tumor is hereditary (passed through the genes from a parent or relative to a child). As the kidney cells are forming in the fetus, some of the cells do not grow properly and form a tumor or create conditions in which a tumor can form later. There is no known cause for a Wilms tumor.

Who gets a Wilms tumor?

The Wilms tumor is the most common type of renal tumor, affecting boys and girls equally and accounting for about 7% of all pediatric cancers. Although it’s possible to find a Wilms tumor in children from birth through 15 years of age, it is more commonly found in children ages 3 to 4 and is much less common after a child reaches the age of 5. There are several rare syndromes that greatly increase the chance of having a Wilms tumor.

Syndromes associated with Wilms tumors

WAGR syndrome

WAGR is an acronym that represents the four diseases present in the syndrome: Wilms tumor, aniridia, genitourinary malformations and retardation. Aniridia is a disease that results in the absence of the iris, the colored part of the eye. A genitourinary malformation is a defect that can affect the kidneys, urinary tract, scrotum, penis, testicles, clitoris and ovaries. WAGR syndrome is linked to the loss or inactivation of the WT1 gene on chromosome 11, which is a gene that usually controls cell growth and suppresses the growth of tumors.

Denys-Drash syndrome

Associated with kidney failure as well as genitourinary malformations (a defect that can affect the kidneys, urinary tract, scrotum, penis, testicles, clitoris and ovaries), this syndrome is also linked to the loss or inactivation of the WT1 gene on chromosome 11.

Beckwith-Wiedemann syndrome

Also due to an abnormality of chromosome 11, this syndrome is linked to an overactive gene called IGF2, which controls cell growth. Characterized by numerous abnormalities, symptoms of Beckwith-Wiedemann syndrome include:

  • Higher than average birth weight
  • An enlarged tongue, spleen and liver
  • Asymmetric (uneven) growth of the body
  • Malformations around the ear
  • Omphalocele (defects on the abdominal wall near the navel)
  • Tumors on the liver and adrenal glands
  • Low blood sugar in the neonatal period

What are the signs and symptoms of a Wilms tumor?

There are many signs and symptoms associated with Wilms tumors, though many are not specific to this condition. Some of the more obvious signs include:

  • An abdominal mass
  • Hematuria (blood in the urine)
  • Abdominal swelling
  • Abdominal pain
  • Swollen abdominal veins

If you can feel an abdominal mass, it is important not to press on it. In the rare case that it is a tumor, pressing on the mass may cause the tumor to rupture.

Other signs and symptoms of a Wilms tumor include:

How do we diagnose Wilms tumor?

We start with a physical examination of your child to see if they are showing any obvious signs or symptoms, followed by blood and urine tests. These tests tell your doctor how well the kidneys are working.

If signs point to a possible tumor, your doctor will schedule an image to be taken of your child’s abdomen. These tests may include an ultrasound, a computerized tomography (CT) scan or magnetic resonance imaging (MRI).

If the images show a tumor, your doctor will schedule a surgery to remove the tumor. Any further steps after the surgery will depend on what the doctor discovers during the surgery.

Why choose us for the diagnosis of Wilms tumor?

While many hospitals only see 1 to 2 cases of pediatric Wilms tumor per year. Caregivers in our Urologic Tumor Program see about 15 cases per year, making us one of the highest volume programs in the country. This higher volume has helped our oncology team become better at identifying the signs and symptoms of Wilms tumor, which leads to a correct diagnosis more quickly. We can complete all tests and imaging in one day, reducing stress on your child and family. From our nurses to technicians to certified child life specialists, we are experts at making your child feel comfortable throughout testing and treatment.

How is Wilms tumor treated?

Most cases of Wilms tumor are treatable, and many can be cured. If a Wilms tumor has formed on a kidney, we will need to remove the tumor, and in some cases, the entire kidney. The surgery to remove a kidney is called a nephrectomy.

The surgical treatment requires close observation by an oncologist (medical physician specialized in cancer). It may also require further surgery, chemotherapy, radiation and routine imaging to see if the cancer has spread or returned.

Why choose us for the treatment of your child’s Wilms tumor?

At Children’s Colorado, experts in our Urologic Tumor Program have extensive experience treating Wilms tumor in kids. Because we see more cases of Wilms tumor than most hospitals, we are able to produce the best prognosis and outcomes in the region. We’re also fortunate to have one of the few pediatric urologists in the world who is also fellowship-trained in urologic oncology, Nicholas Cost, MD.

In some cases of Wilms tumor, we can offer minimally invasive surgery, which ensures the highest precision possible. This option also allows for shorter recovery time, helping children get back to their normal lives faster.

As an academic medical institution, we lead cutting edge research for kidney cancer in children and have access to the most advanced treatments available. Learn more about our urology clinical trials and research.

Helpful Wilms tumor resources

For additional information about Wilms tumor, we recommend the following resources:

PRODWEBSERVER2