Wilms Tumor (Nephroblastoma)

If your child exhibits signs or symptoms of a possible kidney problem, a pediatrician will conduct a physical examination and may order blood, urine, and imaging tests, as well as a tissue biopsy of the kidney. Treatment options will depend on the test results.

Imaging tests are an important tool in diagnosing Wilms tumor because they provide doctors with precise, detailed, 3D views of the kidneys. With this information, a decision can be made as to whether surgery is necessary.

When diagnosing Wilms tumor, doctors order tests to determine whether the cancer has spread to another part of the body (metastasis), or from which area the cancer originally developed. A biopsy is almost always done for accurate diagnosis.

The following tests are commonly used to diagnose Wilms tumor:

• Blood and urine tests. Blood and urine tests are used to evaluate how well the kidneys and liver are functioning.
• Biopsy and surgery. If it is suspected that a child may have Stage I or Stage II Wilms tumor, the surgeon will usually perform an abdominal laparotomy. This surgery removes the tumor and the affected kidney. Sometimes, however, the tumor may be too large or abnormally shaped. In these cases, the surgeon will remove a small piece of kidney tissue for biopsy. After the tissue is analyzed, the surgeon can then determine which course of treatment to proceed with.
  • Chromosome tests. If Wilms tumor is suspected, a pathologist (a doctor who interprets laboratory test results and evaluates cells, tissues, and organs to diagnose diseases) may test the removed kidney tissue for changes in the chromosomes. Wilms tumors resulting from chromosome mutations must follow a different course of treatment than the standard treatment.

Imaging tests

• X-ray use a small amount of radiation to produce images of internal organs, bones, tissues, and tumors.
• Ultrasound is a painless test that uses sound waves to create images of internal organs that can then be assessed from a monitor. Changes in the sound waves create an image that could indicate a tumor.
• Computed tomography (CT or CAT) scan creates images of internal organs and structures of the body from varied angles. The computer then combines the images into a single detailed, 3D image that shows any abnormal structures or tumors. This type of scan can measure the exact size of the tumor. Sometimes a special dye, called contrast, is either injected or administered as a pill or liquid into the area being assessed. This contrast can reveal a much sharper image.
• Magnetic resonance imaging (MRI) scan uses magnetic fields to create detailed images of internal organs. An MRI can show the tumor’s size. Sometimes contrast dye is administered to produce a sharper image with more visible detail.
• Bone scans and bone X-rays are used to detect bone cancer in children with a rare kidney tumor called clear cell sarcoma. A small amount of radioactive material, called a radioactive tracer, is injected into a person’s vein. A special camera is used to view the bones. Lighter-colored bones indicate healthy bones; bones that appear dark show areas of injury or cancer.
• Positron emission tomography (PET) scan involves an injection of a radioactive tracer to help detect cancerous cells. Combined with a CT scan, a PET scan can be useful in determining changes in the size of a tumor after chemotherapy and radiation treatments.

Once diagnostic testing is completed, the doctor will review the results with the patient. The outcome of these tests will help doctors determine whether the child has Wilms tumor and, if so, at the stage of the cancer.