What Is Wilms Tumor?

Wilms tumor is a type of kidney cancer. It can affect both kidneys, but usually develops in just one. With treatment, Wilms tumor is curable in most children.

What Are the Signs & Symptoms of Wilms Tumor?

Children with Wilms tumor (also known as nephroblastoma) usually have a swelling or bump in their belly. Often, there are no other symptoms. But some children may also have:

• nausea
• belly pain
• high blood pressure (hypertension)
• blood in the pee
• a loss of appetite
• a fever

What Causes Wilms Tumor?

Most of the time, Wilms tumor is caused by a gene change (mutation). The gene change causes the kidney cells to develop into a tumor. Doctors don’t know why these gene changes happen. 

Wilms tumor usually happens in kids who are otherwise healthy. But some kinds of genetic syndromes make children more likely to get it. These include:

• Beckwith-Wiedemann syndrome (larger-than-normal internal organs)
• WAGR (problems with the iris, kidneys, urinary tract, genitalia, and intellectual development)
• Denys-Drash syndrome (problems with the kidneys and how the genitalia was formed)

Children with these syndromes need to have frequent ultrasounds until they are at least 8 years old to check for Wilms tumor.

How Is Wilms Tumor Diagnosed?

Wilms tumor is sometimes diagnosed after a parent notices a smooth lump in their child’s belly. Doctors do an exam and order tests such as:

• an ultrasound
• X-rays
• an MRI
• a CT scan
• bone scans
• blood tests and urine tests
• genetic testing

A child with a higher risk for Wilms tumor may be diagnosed if a regularly scheduled ultrasound shows a tumor.

How Is Wilms Tumor Treated?

Pediatric oncologists (cancer doctors for kids) and surgeons work together to treat Wilms tumor. Most children have part or all of their kidney removed (a partial or complete nephrectomy) and chemotherapy. Some children also need radiation therapy. Chemotherapy and/or radiation can be done:

• before surgery to shrink the tumor
• after surgery to kill any remaining cancer cells

What Else Should I Know?

If your child has Wilms tumor, it can be a stressful time. Every child is different, but most children recover from Wilms tumor and go on to live a long, healthy life.

To find support, talk to your doctor, a hospital social worker, a counselor, or a Child Life specialist. Many resources are available to help your child and the whole family. 

You also can find more information and support online at:

• American Cancer Society
• National Cancer Institute