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Wilms Tumor

What Is Wilms Tumor?

Wilms tumor is a rare kidney cancer that is highly treatable. Most kids with Wilms tumor survive and go on to live normal, healthy lives.

Also known as nephroblastoma, Wilms tumor can affect both kidneys, but usually develops in just one. Doctors believe that the tumor begins to grow as a fetus develops in the womb, with some cells that should form into the kidneys instead forming a tumor.

What Are the Signs & Symptoms of Wilms Tumor?

Before being diagnosed with Wilms tumor, most children do not show any signs of having cancer, and usually act and play normally. Often, a parent discovers a firm, smooth lump in the child's abdomen (belly). It is not uncommon for the mass to grow quite large before it is discovered. In fact, the average Wilms tumor is 1 pound at diagnosis.

Some children also may have:

Even though Wilms tumors often are large when found, most have not spread to other areas of the body. This makes it easier to successfully treat than if the cancer cells have spread (metastasized) to other parts of the body.

How Is Wilms Tumor Diagnosed?

Several tests are used to confirm a Wilms tumor diagnosis and determine the stage of the disease. These tests can include:

  • Ultrasound: usually the first test done, it uses sound waves instead of X-rays to make an image of the area.
  • CT/CAT scan: makes a detailed cross-sectional view of an organ through X-rays. It is extremely useful in finding tumors and seeing whether the cancer has spread (metastasized).
  • MRI: uses radio waves and strong magnets to make detailed pictures of the internal parts of the body. This lets doctors see if the cancer is in any major blood vessels near the kidney.
  • X-rays: to look for any metastasized areas, especially in the lungs.
  • Bone scans: uses small amounts of radioactive material to highlight any areas of diseased bone.
  • Lab tests: such as blood tests and urine tests to check a child's general health and to detect any adverse side effects (such as low red or white blood cell counts) of the treatment.

What Causes Wilms Tumor?

Some genetic factors (like birth defect syndromes) can make a child more likely to develop Wilms tumor, including:

  • a family history or personal history of Beckwith-Wiedemann syndrome (a condition associated with larger-than-normal internal organs)
  • WAGR (marked by defects of the iris, kidneys, urinary tract, or genitalia)
  • Denys-Drash syndrome (a defect of the genitalia)

Kids with risk factors for Wilms tumor should have an ultrasound screening every 3 months until about age 6 or 7. Those at high risk may get be screened until they're a little older.

How Is Wilms Tumor Treated?

Treating Wilms tumor depends on a few things. Most important are the stage of the cancer at diagnosis, and the condition, or histology , of the cancer cells. Most Wilms tumors have "favorable" histology, meaing they are easier to cure.

Doctors use a staging system to describe the extent of a tumor. A very aggressive tumor is treated with an intensive regimen of medicine to achieve the best chance for a cure. A child with less-invasive disease will get the least amount of medicine needed, which helps reduce long-term side effects.

The most common stages are:

  • Stage I: Cancer is found in one kidney only and can be completely removed by surgery. About 41% of all Wilms tumors are stage I.
  • Stage II: Cancer has spread beyond the kidney to the surrounding area, but can be completely removed by surgery. About 23% are stage II.
  • Stage III: Cancer has not spread beyond the abdomen, but cannot be completely removed by surgery. About 23% are stage III.

Surgery is usually done to treat Wilms tumor. In a radical nephrectomy, the surgeon removes:

  • the tumor
  • the entire kidney
  • its ureter (a tube that carries pee from the kidney to the bladder)
  • its adrenal gland (a gland that sits on top of the kidney)
  • surrounding fatty tissue

When cancer is in both kidneys, surgeons usually take out as much of the cancer as possible and preserve as much healthy kidney tissue as they can to avoid a kidney transplant.

All treatment plans usually include both surgery and chemotherapy. More advanced stages also may require radiation therapy. Both treatments have short-term and long-term risks.

Short-term (or temporary) effects may include:

  • nausea and vomiting
  • loss of appetite
  • mouth sores
  • tiredness
  • hair loss
  • a weakened immune system
  • bleeding or bruising

Long-term (or late) effects may include:

  • the development of secondary cancers (like leukemia)
  • weakening of some internal organs, such as the heart
    However, the benefits of treatment far outweigh these risks.

How Can I Help MY Child?

Parents might feel unsure about whether they can care for their child after treatment in a hospital. The hospital's doctors, nurses, and home health services staff will provide the information and support needed to help a parent care for a child after or between hospital visits.

Depending on the treatment, the level of at-home care can vary. Treatment for Wilms tumor is not as intensive as for other cancers, so most kids won't have lots of things they can't do.

Most kids treated for Wilms tumor don't have special nutritional needs. They also don't have to take medicine for low blood cell counts, as most other cancer patients do. However, parents must watch for signs of problems, like fever, nausea, vomiting, or diarrhea. A child with a high fever should see a doctor right away.

When therapy is over, the care team will provide a schedule of follow-up tests such as:

  • chest X-rays or CAT scans
  • blood tests
  • a physical exam

If the cancer comes back, treatment will be based on its histology, and how long it's been since the last treatment. The longer the cancer was gone, the better. But Wilms tumor usually does not come back. Being cancer-free for at least 2 years after treatment is generally a very good sign.

Reviewed by: Gregory C. Griffin, MD
Date Reviewed: Aug 15, 2016

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