Wilms tumors are usually brought to a doctor's attention as the result of signs or symptoms a child is having. But even if the doctor thinks a child has Wilms tumor because of the results of a physical exam or imaging tests, the diagnosis needs to be confirmed by looking at a sample of the tumor under a microscope.

Signs and symptoms of Wilms tumor

Wilms tumors can be hard to find early because they can grow quite large without causing any pain. Children may look healthy and play normally. The first sign is usually swelling in the abdomen. Parents may notice the swelling or a hard mass in the child's belly while bathing or dressing the child. It feels firm and is often large enough to be felt on both sides of the belly. It is usually not painful. Some children with Wilms tumor may also have stomach pain, fever, nausea, loss of appetite, constipation, or blood in the urine.

Other problems may also cause many of these symptoms, and they do not necessarily mean your child has a tumor. Still, if your child's symptoms suggest that a tumor may be present, check with your child's doctor so that the cause can be evaluated and treated, if needed.

Medical history and physical exam

If your child has symptoms that suggest a tumor may be present, your child's doctor will take a complete medical history. This will probably include questions about any symptoms, as well as if there's a family history of cancer or birth defects, especially in the genitals or urinary system.

The doctor will examine your child to look for possible signs of Wilms tumor or other health problems. The main focus will likely be on the abdomen and on any increase in blood pressure, which is another possible sign of this cancer.

Imaging tests

If the doctor thinks your child might have a kidney tumor, he or she will probably order imaging tests. These tests use x-rays, magnetic fields, or radioactive substances to create pictures of the inside of the body. Imaging tests are done for a number of reasons, including:

• to help find out if a tumor is in the kidney(s) and if it is likely to be a Wilms tumor

• to learn how far the tumor may have spread, both within the kidney and to other parts of the body

• to help guide surgery or radiation therapy

• to help determine if treatment has been effective

Ultrasound (ultrasonography)

Ultrasound uses sound waves to create images of internal organs. For this test, a small, microphone-like instrument called a transducer is placed on the skin near the kidney. It emits sound waves and picks up the echoes as they bounce off the tissues in the kidney. The echoes are converted by a computer into a black and white image that is displayed on a computer screen. The echo patterns made by most kidney tumors look different from those of normal kidney tissue. Different echo patterns also can distinguish some types of cancerous and non-cancerous kidney tumors from one another. In addition, ultrasound is very useful when looking for tumor thrombus (tumor growing into the main veins around the kidney. This is helpful in planning the extent of surgery.

This is often the first imaging test done if the doctor suspects your child has Wilms tumor because it is painless, does not involve radiation, and allows the doctor to see the entire abdomen.

Computed tomography (CT, CAT) scan

The CT scan is an x-ray test that produces detailed cross-sectional images of parts of your child's body. Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around your child while he or she lies on a table. A computer then combines these pictures into images of slices of the part of the body being studied. Unlike a regular x-ray, a CT scan creates detailed images of the soft tissues in the body.

Before the scan, your child may be asked to drink a contrast solution and/or get an intravenous (IV) injection of a contrast dye that helps better outline abnormal areas in the body. Your child may need an IV line through which the contrast dye is injected. The contrast may cause some flushing (a feeling of warmth, especially in the face). Some people are allergic and get hives. Rarely, more serious reactions like trouble breathing or low blood pressure can occur. Be sure to tell the doctor if your child has any allergies or has ever had a reaction to any contrast material used for x-rays.

CT scans take longer than regular x-rays. Your child will need to lie still on a table while they are being done. During the test, the table moves in and out of the scanner, a ring-shaped machine that completely surrounds the table. Some people feel a bit confined by the ring they have to lie in while the pictures are being taken. Some doctors may give younger children, medicine to help keep them calm or even asleep during the test.

Spiral CT (also known as helical CT) is now available in many medical centers. This type of CT scan uses a faster machine. The scanner part of the machine rotates around the body continuously, allowing doctors to collect the images much quicker than with standard CT. This lowers the chance of images blurring as a result of breathing motion. It also lowers the dose of radiation received during the test. The slices it images are thinner, which yields more detailed pictures.

CT scanning is one of the most useful tests in finding a mass inside the kidney. It is also useful in checking whether a cancer has spread to organs and tissues beyond the kidney, such as the lungs.

Magnetic resonance imaging (MRI) scan

Like CT scans, MRI scans provide detailed images of soft tissues in the body. But MRI scans use radio waves and strong magnets instead of x-rays (and therefore don't expose your child to radiation). The energy from the radio waves is absorbed and then released in a pattern formed by the type of body tissue and by certain diseases. A computer translates the pattern into a very detailed image of parts of the body. A contrast material called gadolinium may be injected into a vein before the scan to better see details. The contrast material usually does not cause allergic reactions.

MRI scans take longer than CT scans -- often up to an hour. Your child may have to lie inside a narrow tube, which is confining and can be distressing, so sedation is sometimes needed. Newer, more open MRI machines may be another option. The MRI machine makes loud buzzing and clicking noises that your child may find disturbing. Some places provide headphones or earplugs to help block this out.

MRI scans show more detailed images than CT and ultrasound. They may be done if there's a chance that the cancer involves a major vein in the abdomen (the inferior vena cava). They may also be used to look for possible spread of cancer to the brain or spinal cord if doctors are concerned the cancer may have spread there.

Chest x-ray

In most cases, a chest x-ray will be done to look for any spread of Wilms tumor to the lungs, as well as to have a baseline view of the lungs to compare with other x-rays that might be done in the future.

Bone scan

For this test, a small amount of low-level radioactive material is injected into a vein (intravenously, or IV). The substance settles in areas of damaged bone throughout the entire skeleton over the course of a couple of hours. Your child then lies on a table for about 30 minutes while a special camera detects the radioactivity and creates a picture of the skeleton.

Areas of active bone changes appear as "hot spots" on the skeleton -- that is, they attract the radioactivity. These areas may suggest the presence of cancer, but other bone diseases can also cause the same pattern. To distinguish between these conditions, other imaging tests such as plain x-rays or MRI scans, or even a bone biopsy might be needed.

Bone scans can help find cancer that has spread to bones. Doctors don't usually order this test unless they think your child has a type of Wilms tumor that is likely to spread.

Lab tests

A urine sample may be tested (urinalysis) to look for blood and other substances in the urine. The 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 gland, which lies just above the kidney.)

Blood tests are not used to find Wilms tumors, but they may be done to check a child's general health (especially before surgery) and to look for side effects during treatment such as chemotherapy. These may include tests to count the number of white blood cells, red blood cells, and blood platelets, and tests to measure certain chemicals and salts in the blood that give clues about how well the liver and kidneys are working.

Kidney biopsy/surgery

In most cases, imaging tests can give doctors enough information to decide if a child probably has a Wilms tumor, and therefore surgery should be done. But the actual diagnosis of Wilms tumor is made when a sample of the tumor is removed and looked at under a microscope. The cells in Wilms tumors have a characteristic appearance when looked at this way. This is also when doctors determine the histology of the Wilms tumor (favorable or unfavorable), as was described in the section "What is Wilms tumor?"

In most cases, the sample is obtained during surgery to treat the tumor (see the "Surgery" section in "How is Wilms tumor treated?"). Less often, the sample to confirm the diagnosis is obtained during a biopsy as a separate procedure before surgery to treat the tumor. The biopsy may be done either surgically or with a long, hollow needle.

Last Medical Review: 09/14/2009
Last Revised: 09/14/2009