The cause of Wilms tumor is not known, but some children may have a genetic abnormality that increases their risk of developing this tumor.
Children usually have a lump in the abdomen, and they may also have abdominal pain, fever, poor appetite, nausea, and vomiting.
An imaging test is done to determine the nature and size of the lump.
Treatment involves surgery and chemotherapy and sometimes radiation therapy.
(See also Overview of Childhood Cancer Overview of Childhood Cancer In the United States, the overall incidence of cancer in children and adolescents has increased over time. From 1975 to 2022, rates increased by approximately 0.8 per 100,000 each year. However... read more .)
Wilms tumor usually develops in children younger than 5 years old, although it occasionally occurs in older children. It is very rare in adults. In about 5% of cases, Wilms tumor occurs simultaneously in both kidneys.
The cause of Wilms tumor is not known, although a lack of certain genes or another genetic abnormality may be involved in some cases.
Wilms tumor develops in some children with certain birth defects, especially of the kidneys, genitals, and urinary tract, and in children who are missing both irises or have one side of the body that grows too much. These defects, as well as intellectual disability, may be caused by a genetic abnormality. However, most children with Wilms tumor do not have recognizable abnormalities.
Symptoms of Wilms Tumor
The most common symptom of Wilms tumor is a painless lump in the abdomen. The abdomen may enlarge, which parents may notice when children suddenly need a larger diaper size.
Less often, children may have abdominal pain, fever, poor appetite, nausea, and vomiting. Blood appears in the urine of some children.
Because the kidneys are involved in controlling blood pressure, Wilms tumor may cause high blood pressure High Blood Pressure High blood pressure (hypertension) is persistently high pressure in the arteries. Often no cause for high blood pressure can be identified, but sometimes it occurs as a result of an underlying... read more 
(hypertension).
This cancer can spread to other parts of the body, especially the lungs. If the lungs are involved, children may cough and be short of breath.
Diagnosis of Wilms Tumor
Ultrasonography, computed tomography (CT), or magnetic resonance imaging (MRI) of the abdomen
Often surgery to remove the tumor at the time of diagnosis
Wilms tumor is most often detected when parents notice a lump in the child’s abdomen and take their child to a doctor. Or a doctor may feel such a lump during a routine examination.
If the doctor suspects Wilms tumor, several imaging tests are done. Ultrasonography of the abdomen is done to determine the nature and size of the lump. CT Computed Tomography (CT) In computed tomography (CT), which used to be called computed axial tomography (CAT), an x-ray source and x-ray detector rotate around a person. In modern scanners, the x-ray detector usually... read more 
or MRI Magnetic Resonance Imaging (MRI) In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more 
of the abdomen is done to help doctors determine whether the tumor has spread to nearby lymph nodes or the liver and determine whether the other kidney is affected.
The doctor also does CT of the chest to determine whether tumors have spread to the lungs.
Surgery to remove part or all of the kidney (nephrectomy) that contains the tumor is done in most children based on the results of the imaging tests. Doctors then analyze the tumor to confirm that it is a Wilms tumor.
During surgery, doctors also remove nearby lymph nodes in the abdomen and analyze them for cancer cells. Cancer that has spread to the lymph nodes may require different treatment than cancer that has not.
Treatment of Wilms Tumor
Surgery and chemotherapy
Sometimes radiation therapy
(See also Cancer Treatment Principles Cancer Treatment Principles Treating cancer is one of the most complex aspects of medical care. It involves a team that encompasses many types of doctors working together (for example, primary care doctors, gynecologists... read more and Surgery for Cancer Surgery for Cancer Surgery is a traditional form of cancer treatment. It is the most effective in eliminating most types of cancer before it has spread to lymph nodes or distant sites (metastasized). Surgery may... read more .)
Treatment options for Wilms tumor depend on where the child is going to receive treatment. In North America, doctors first remove the kidney that contains the tumor and then give the child chemotherapy drugs Chemotherapy and Other Systemic Cancer Treatments Systemic treatments are those that have effects throughout the body rather than being applied directly to the cancer. Chemotherapy is a form of systemic treatment that uses drugs to kill cancer... read more . In Europe, doctors first give the child chemotherapy and then remove the tumor. In both locations, all children are given chemotherapy drugs (most commonly dactinomycin and vincristine and sometimes doxorubicin) after surgery and some children are given radiation therapy.
Some younger children who have small tumors can be cured by surgery alone.
During surgery, the other kidney is examined to determine whether it also has a tumor.
Rarely the tumor is extremely large and cannot be removed initially or tumors are in both kidneys. In such cases, children are first treated with chemotherapy to shrink the tumor or tumors. Then the tumor or tumors are removed.
If the cancer has spread significantly, children are also treated with radiation therapy Radiation Therapy for Cancer Radiation is a form of intense energy generated by a radioactive substance, such as cobalt, or by specialized equipment, such as an atomic particle (linear) accelerator. Radiation preferentially... read more .
Prognosis for Wilms Tumor
In general, Wilms tumor is very curable.
If the tumor is only in the kidney, about 85% to 95% of children are cured. Even if the tumor has spread beyond the kidney, cure rates range from 60% to 90% depending on how abnormal the cancer cells appear during testing.
The outcome is usually better in children who
Are younger
Have cancer cells that are less abnormal when the tumor is examined under a microscope
Have a tumor that has not spread
Do not have certain gene abnormalities
Wilms tumor can return, typically within 2 years of diagnosis. Children whose cancer has returned can still be cured.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
American Cancer Society: If Your Child Is Diagnosed With Cancer: A resource for parents and loved ones of a child who has cancer that provides information about how to cope with some of the problems and questions that come up just after a child is diagnosed
