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ºÙºÙÊÓƵ specialists are experienced at diagnosing Wilms tumor, also called nephroblastoma, the most common type of kidney cancer in children. It is typically diagnosed in children around age 3 and is rarely diagnosed in those who are older than 6 years of age.

About 6 percent of all childhood cancers are Wilms tumors. The condition is named after the doctor who first wrote about this cancer in medical journals.

Wilms tumor typically affects one kidney, although some children develop tumors in both kidneys. One type, known as an anaplastic Wilms tumor, tends to grow more rapidly and doesn’t respond as well to treatment as others. Anaplastic tumors account for about 10 percent of Wilms tumors.

Rarely, the cancer spreads, or metastasizes, to other organs, such as the lungs. The tumor may grow into the renal vein, which drains blood from the kidney. It may spread to the inferior vena cava, a large vein that carries blood from the lower half of the body to the heart, necessitating surgery.

Since a Wilms tumor usually doesn’t cause symptoms, it is often found when a parent or doctor notices that the child’s abdomen seems distended, or a mass or lump is detected. If the child does experience symptoms, they may include abdominal pain, unexplained fever, a loss of appetite, nausea, and vomiting. Signs of a Wilms tumor may include blood in the urine or high blood pressure.

There is no known cause of a Wilms tumor. However, having certain birth defects—such as hypospadias, in which a boy’s urinary opening is not located at the tip of the penis—is associated with Wilms tumor. Other rare conditions associated with Wilms tumor include hemihypertrophy, in which one side of the body is larger than the other; and aniridia, in which the eye is colorless. Both boys and girls can be diagnosed with this cancer.

Your child’s doctor takes a medical history to determine how long your child has had symptoms, if any. He or she also conducts a physical exam and takes your child’s blood pressure. Next, the doctor performs several tests to diagnose the condition.

Doctors may perform surgery to confirm the diagnosis, as well as remove the tumor.

Your child's doctors determine how advanced the tumor is by taking into account whether the cancer has spread outside the kidney, if it appears in both kidneys, and if it can be completely removed during surgery.

Blood Test

ºÙºÙÊÓƵ technicians take a sample of your child’s blood to check the levels of creatinine, a waste product that the kidneys remove from the body. This helps doctors to assess your child’s kidney function. The doctor also checks the number of red and white blood cells and platelets, which provide an overview of your child’s health.

Urine Test

Your child’s doctor may ask for a urine sample so that he or she can check for blood in the urine, as well as for neurotransmitters called catecholamines, such as homovanillic acid (HVA) and vanillylmandelic acid (VMA). These may be signs of a tumor called a neuroblastoma, which often starts in the adrenal glands above the kidneys. A neuroblastoma requires different treatment from a Wilms tumor.

Abdominal Ultrasound

Ultrasound uses sound waves to create images of the kidneys and other organs in the abdomen, making any tumors visible on a computer screen. In this test, which is performed in the doctor’s office, your child lies on a table and a warm gel is spread on his or her abdomen. A handheld device called a transducer is placed on the skin. It sends images to a computer for the doctor’s review.

CT Scan

A CT scan uses X-rays and a computer to create three-dimensional, cross-sectional images of the abdominal organs. It can detect a tumor and determine its size and whether it affects one or both kidneys. A CT scan can also help determine if a tumor has spread to the liver, lungs, or nearby lymph nodes.

Before the scan, your child may be given a contrast agent or dye, which is taken by mouth, to highlight the organs during the test. To help your child remain still during the test, a pediatric anesthesiologist may recommend sedation. The test takes 30 to 45 minutes.

If you accompany your child to the CT scan, you must wear a lead apron to avoid radiation exposure. Pregnant women are advised not to be in the room while the machine is operating.

Surgical Biopsy

Lymph nodes—small glands located throughout the body that assist in immune function—are often the first place cancer spreads. When your child’s surgeon removes the tumor, he or she also removes the lymph nodes near the kidney to see if cancer cells are present. Cells collected from the tumor and lymph nodes are examined under a microscope by a pathologist.

A Wilms tumor is typically large enough that the entire kidney must be removed. For small tumors, part of the kidney may be removed. If both kidneys have tumors, parts of each kidney are usually removed.

Most people can function well with only one kidney or parts of both kidneys. Your child’s doctor may recommend regular blood and urine tests to monitor kidney function.

Bone Scan

A bone scan takes images of the bones to look for tumors. This test is performed only if the results of other imaging tests cause your doctor to suspect that cancer has spread to the bones.

Before the test, a small amount of a radioactive material is injected into a vein in the arm to make any tumors more visible. A bone scan can take 30 to 60 minutes to complete, and it may require sedation.