Wilm's Tumor

Alternative names: tumor - Wilms; kidney tumor; nephroblastoma

Definition: A cancerous tumor of the kidney that occurs in children.

Causes, incidence, and risk factors: Wilms' tumor is the most common intraabdominal tumor in children and the most common type of kidney tumor. The exact cause of tumor formation is unknown, but it probably develops in fetal tissue. It is associated with certain congenital defects including urinary tract abnormalities, absence of the iris (aniridia) and hemihypertrophy (enlargement of one side of the body), and shows an increased incidence among siblings and twins, which suggests a possible genetic cause.

The tumor may become quite large, but usually remains encapsulated (self enclosed). It may spread to other body tissues. The frequency of disease occurrence is estimated to be about 1 out of 200,000 to 250,000 children. The peak incidence is at 3 years old. Rarely, the tumor may be present in adults.


  • abdominal pain
  • swelling in the abdomen (abdominal hernia or mass)
  • blood in the urine (occurs in less than 1/4 of children)
  • fever
  • loss of appetite
  • nausea
  • vomiting
  • general discomfort or uneasiness (malaise)
  • blood pressure, high
  • constipation
  • increased growth on only one side of the body (hemihypertrophy)

Note: Abnormal urine color may also be associated with this disease. A missing iris of the eye (aniridia) is an associated congenital abnormality.

Caution: Avoid palpation of the abdomen, and use care during bathing and handling to avoid trauma to the tumor site.

Signs and tests: Special emphasis is placed on the history and physical exam: looking for a family history of cancer and for associated congenital anomalies in the child. The physical examination reveals an abdominal mass. High blood pressure may be present.

Tests include:

  • CBC (may show anemia)
  • BUN
  • creatinine
  • creatinine clearance (may be decreased)
  • urinalysis (blood and/or protein in urine)
  • abdominal X-ray
  • chest X-ray (may demonstrate metastasis)
  • intravenous pyelogram (distortion of the kidney)
  • CT scan of the abdomen (abdominal mass arising from kidney)
  • Other tests may be required to determine if the tumor has spread.

Treatment: Clinical staging of the tumor is done to determine the extent of the tumor and to maximize the effectiveness of treatment plans. Surgical exploration and removal of the tumor is performed as soon as possible. Regional lymph nodes, abdominal organs, and other tissues are examined and removed if the tumor has spread to those areas. Radiation therapy and chemotherapy will often be started after surgery, depending on the stage of the tumor.

Expectations (prognosis): With treatment, the disease has a high cure rate. Children with a localized tumor have a 90% cure rate when treated with surgery and chemotherapy or surgery, radiation, and chemotherapy combined.

Complications: Spreading of the tumor to the lungs, liver, bone, or brain are the main complications. Removal of a bilateral Wilms tumor may leave the patient with marginal kidney function.

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