Tests for Wilms Tumors

Medical history and physical exam

If your child has signs or symptoms that suggest they might have a Wilms tumor (or another type of kidney tumor), their health care team will want to get a complete medical history. This helps them learn more about the symptoms and how long  they’ve been there.

They may also ask if there’s a family history of cancer or birth defects, especially in the genitals or urinary system, as this might point to an increased risk of Wilms tumors.

The health care team will also do a physical exam to look for possible signs of a kidney tumor or other health problems. The focus will probably be on your child's abdomen (belly) and on any increase in blood pressure, which is another possible sign of a kidney tumor. Blood and urine samples might also be collected and tested (see “Lab tests” below).

Along with a physical exam, the following tests may be used to diagnose a Wilms tumor. Not all tests described here will be used for every child.

Imaging tests

If the health care team thinks your child might have a kidney tumor, they will probably get one or more imaging tests. These tests use sound waves, x-rays, magnetic fields, or radioactive substances to create pictures of the inside of your child’s body. Imaging tests might be done to:

• Help find out if there is a tumor in their kidney(s), and if so, if it's likely to be a Wilms tumor
• Learn if and how far the tumor has spread, both in the kidney(s) and to other parts of the body
• Help guide surgery or radiation therapy
• Look at the area after treatment to help determine if the treatment worked

Ultrasound (sonogram)

If the doctor suspects your child has a tumor in their abdomen, ultrasound is often the first imaging test done. This test does not use radiation, and it gives the doctor a good view of the kidneys and the other organs in the abdomen.

Ultrasound can also show if the tumor is growing into the main veins coming out of the kidney. This information can help in planning for surgery, if it's needed.

Computed tomography (CT, CAT) scan

A CT scan (also called a CAT scan) uses x-rays to make detailed cross-sectional images of parts of your child’s body, including their kidneys.

This is one of the most useful tests to look for a tumor inside the kidney. It’s can also show whether a cancer has grown into nearby veins such as the inferior vena cava (the large vein that carries blood from the lower part of the body to the heart), or if it has spread to organs beyond the kidney, such as the lungs and/or liver.

Your child will need to lie very still on a table while the scans are being done. To help make sure the pictures are clear, younger children may be given medicine to help keep them calm or asleep during the test.

Magnetic resonance imaging (MRI)

An MRI creates detailed images using radio waves and strong magnets instead of x-rays, so there is no radiation involved.

This test might be done if the doctor needs to see very detailed images of the kidney or nearby areas. For example, it might be done if there’s a chance a kidney tumor has reached the inferior vena cava (a major vein in the abdomen).

If doctors are concerned that cancer may have spread to the brain or spinal cord, they might also use an MRI to look for it there.

During an MRI, your child may have to lie inside a narrow tube. This can feel confining, and it can be distressing. They will also have to stay still for several minutes at a time. Younger children may be given medicine to help keep them calm or asleep during the test.

Chest x-ray

Chest x-rays might be done to look for any spread of Wilms tumor to the lungs. A chest x-ray also gives the health care team a baseline view of your child’s lungs. They can compare this to other x-rays in the future. A chest x-ray isn’t needed if a CT scan of the chest is done.

Lab tests

If your child’s health care team suspects a kidney problem, they might order lab tests to check urine and blood samples. Lab tests might also be done after a Wilms tumor is found.

A urine sample may be tested for blood cells, proteins, and other substances to see if there are problems with your child’s kidneys. (This testing is called a urinalysis.)

Urine may also be tested for substances called catecholamines. This is done to make sure your child doesn’t have another kind of tumor called neuroblastoma. (Neuroblastomas often start in the adrenal glands, which are just on top of each kidney.)

Kidney biopsy/surgery

Imaging tests give doctors a lot of information. Most of the time, they can get enough information from these tests to decide if your child most likely has a Wilms tumor, and therefore needs surgery.

But the actual diagnosis of a Wilms tumor is not made from these imaging tests. It is made when a small piece of the tumor is removed and checked under a microscope. The cells in Wilms tumors have a distinct appearance when they are looked at this way.

Doctors also use this sample to determine the histology of the Wilms tumor (favorable or anaplastic), as described in What Are Wilms Tumors?

Most often, this testing is done on the tumor after it is removed during surgery to treat it. Sometimes, a sample of the tumor is taken in a separate procedure before surgery. This procedure is called a biopsy.

Doctors might do a biopsy if they are less certain about the diagnosis, or if they aren’t sure the tumor can be removed completely.

Lab tests of biopsy samples

Biopsy (or surgery) samples are sent to a lab, where they are looked at with a microscope to determine the histology of the Wilms tumor.

Other tests might be done as well. For example, the tumor might be tested to see if the cancer cells have changes in chromosomes 1 and 16. This can often help predict how well treatment will work. Tumors with cells that have changes in these chromosomes might need more intensive treatment. (See Treatment by Type and Stage of Wilms Tumor.)

To learn more about different types of biopsies, how the biopsy samples are tested in the lab, and what the results might tell you, see Testing Biopsy and Cytology Specimens for Cancer.