Wilms tumor is a rare kidney cancer that mainly affects children. It is the most common type of kidney cancer in childhood. It accounts for about 7% of all pediatric cancers. About 500 children in the United States are diagnosed with this each year.

Wilms tumor is also called nephroblastoma. Some people call it Wilms cancer or nephroblastoma cancer. It typically occurs in one kidney. But it can affect both kidneys at the same time.

What Causes Wilms Tumor?

It’s unclear what causes Wilms tumor. Most cases happen by chance. They are caused by genetic mutations (changes) in the kidney cells that happen after birth.

In some cases, patients are born with genetic mutations in all cells. They are at risk for other medical problems as well.

A small number of people with Wilms tumor may also have one of these genetic syndromes:

• WAGR syndrome: "WAGR" stands for the four diseases in this syndrome: Wilms tumor, aniridia (absence of the iris, which is the colored part of the eye), genitourinary malformations and range of developmental delays.
• Denys-Drash syndrome: This condition includes kidney failure, genitourinary malformations and tumors of the ovaries or testes.
• Beckwith-Wiedemann syndrome: This syndrome includes a high birth weight and an enlarged liver, spleen and tongue. The liver and adrenal glands may have tumors.

Cincinnati Children’s takes a collaborative approach with multiple pediatric specialists to provide the best care and outcomes for patients that have these, and other underlying, conditions.

Wilms Tumor Symptoms

Symptoms of Wilms tumor vary widely. Most children (60%) have a lump (tumor) in the abdomen (belly). Many children have no symptoms and Wilms tumor is found on routine exams. Some tumors can be very large, even bigger than the kidney itself.

Cancer cells from the tumor may spread to other parts of the body. The most common site is the lungs. They can also move to the brain and the bones. Additionally, 5% to 10% of children with Wilms tumor have both kidneys affected at time of diagnosis.

A wide range of other symptoms may occur. These include:

• Swelling in the belly
• Pain in the belly
• Blood in the urine (pee)
• Decreased appetite
• Weakness or fatigue
• Fever
• High blood pressure
• Veins that look large or swollen across the belly
• Constipation

How is Wilms Tumor Diagnosed?

Wilms tumor can occur between infancy and age 15. It is often diagnosed before age 10 when a doctor reviews the child’s patient’s medical history and performs an exam.

Additional tests may include:

• Blood and urine tests: These are used to check kidney and liver function.
• Chest X-ray: Images can show if the disease has spread to the lungs.
• Other imaging tests: Abdominal ultrasound, CT scan and/or MRI tests can help doctors understand the tumor and see if the cancer has spread to other areas of the body. Wilms tumor can be diagnosed on imaging alone.
• Biopsy (sometimes needed): This is to look at tissue from the tumor under a microscope to see if it is cancerous.

Children with Wilms tumor typically work with a team of doctors who have different specialties. This can include a pediatric oncologist, pediatric surgeon, radiation oncologist and pathologist. The team works together with the child and family to develop the best treatment plan.

How is Wilms Tumor Treated?

Treatment for Wilms tumor depends on the stage of the disease. This refers to how aggressive the tumor is and if the cancer has spread beyond the kidneys.

Full Nephrectomy

The most common treatment is surgery to remove the tumor and the kidney. Often, the entire kidney is taken, which is a full nephrectomy. When this happens, the remaining kidney takes on the work of both. Sometimes, only part of the kidney is taken, which is a partial nephrectomy.

If Wilms tumor is in both kidneys, sometimes both must be removed. This is extremely rare. If both kidneys are removed, the patient would need kidney dialysis. Kidney dialysis is an ongoing procedure to remove waste products and extra water from the blood. Surgeons also remove lymph nodes during surgery to see if the cancer has spread. A lymph node is a small, bean-shaped structure that helps filter fluid in the body.

Other Treatments

In addition to surgery, patients may undergo other treatments for Wilms tumor. These include:

• Medications: Medicines can help to control pain, hypertension (high blood pressure), nausea and infections.
• Chemotherapy: These are drugs that help shrink tumors before surgery or eliminate any cancer cells after surgery. Chemotherapy can reduce the risk of the cancer spreading or happening again. Most Wilms tumors will require chemotherapy for best outcomes.
• Radiation: With radiation therapy, beams of intense energy are used to kill cancer cells to keep them from spreading or coming back. Radiation may be used in patients with more advanced disease or with risk factors for return of the disease.

Recovery After Surgery for Wilms Tumor

Cincinnati Children’s started a protocol called enhanced recovery after surgery (ERAS) a few years ago. It helps patients recover faster from surgery.

ERAS includes eating carbohydrates before surgery to reduce fasting, and feeding early after surgery to help normal digestion. It also uses fewer narcotics, such as codeine and morphine, for pain during and after surgery. This reduces potential side effects such as nausea, vomiting and constipation.

ERAS also includes reducing the amount of intravenous fluids given during and after surgery to decrease swelling throughout the body.

Before ERAS, patients would stay in the hospital for an average of seven days after surgery. With ERAS, they generally go home after three or four days. ERAS has enhanced the quality of life for children who have surgery for Wilms tumor.

Wilms Tumor Outlook

Patients with Wilms tumor need to continue to see their doctor for regular follow-up visits. Doctors will check the patient’s response to treatment and manage any side effects. They also will watch to see if the disease comes back and monitor the function of the remaining kidney.

The overall cure rate for Wilms tumor is 80% to 90%. With expert management and treatment, most children have a positive outcome. But like any cancer, the prognosis for Wilms tumor varies for each patient. The cancer can come back.

Cincinnati Children's participates in the Children's Oncology Group (COG). The COG is a research group of children's hospitals across the country. Because pediatric cancer is so rare, this national network of experts works together to improve care through studies and knowledge sharing.

Working with the COG, Cincinnati Children’s follows the treatment protocols that research has shown to be the most effective. Research is ongoing. New methods are continually being discovered to improve treatment and outcomes.