Wilms' tumour

A Wilms’ tumour is a malignant (cancerous) tumour that develops in the kidney from specialised cells called nephroblasts. It is also called a nephroblastoma.

In this section

Usually, this tumour occurs in only one kidney (unilateral), although occasionally there may be tumours in both kidneys (bilateral). Sometimes the tumour can spread (metastasise) to other parts of the body, such as the lungs or liver.

Approximately one in ten thousand children get Wilms’ tumour. About 70 children develop Wilms’ tumour in the UK each year. It most often affects children below the age of five and is slightly more common in girls than boys.

In most cases there is no known cause for Wilms’ tumour, although a small number of children have a genetic tendency. This is usually obvious, either because other members of the family have had Wilms’ tumour or because the child has certain growth or development problems that have been present from birth. However, for the majority of children with Wilms’ tumour, there is no genetic tendency, nor is there any increased risk in brothers or sisters.

Signs and symptoms

The most common symptom of Wilms’ tumour is swelling of the abdomen (tummy). This is usually painless. Other symptoms may include:

  • nausea and vomiting
  • poor appetite
  • weight loss
  • abdominal pain
  • fever
  • red urine due to blood in the urine
  • high blood pressure.

Tests and investigations

Your doctors will need to carry out some tests to find out as much as possible about the type, position and size of the tumour. The tests will include:

  • urine and blood samples to show how well the kidneys are working as well as some other information about general health
  • chest X-ray to show if the tumour has spread to the lungs
  • ultrasound scan to show the position and size of the tumour
  • CT scan to give more detailed information about the tumour and show if it has spread
  • biopsy, a small operation, usually carried out under general anaesthetic, in which a surgeon removes a small piece of tissue from the kidney to help make a diagnosis.


The tumour stage is a measure of how far the tumour has spread beyond the kidney. This can only be measured accurately after surgery to remove the affected kidney. Knowing the particular type and stage of the cancer helps the doctors decide on the most appropriate treatment.

The following describes the staging system used for Wilms’ tumours:

  • Stage I: the tumour is confined to the kidney and is completely removed at the time of surgery
  • Stage II: the tumour has broken through the kidney lining but is still completely removed at the time of surgery
  • Stage III: some of the tumour is left behind at the time of surgery, either because the tumour breaks or because complete surgical removal is not possible
  • Stage IV: the tumour has spread to other parts of the body, usually the lungs or lymph nodes (glands)
  • Stage V: there is tumour in both kidneys (bilateral disease).

Treatment of Wilms’ tumour

Treatment for Wilms’ tumour usually includes surgery, chemotherapy or radiotherapy, or a combination of these.


All children with Wilms’ tumour will have surgery to remove the affected kidney. If both your child’s kidneys are affected, part of both kidneys may need to be removed. However, we will first give your child chemotherapy to shrink the tumour; this will make the surgery easier when it is carried out later and will reduce the need for radiotherapy.


Radiotherapy may be used after surgery to destroy any remaining tumour cells. See the Children’s Unit booklet Radiotherapy treatment for more details on this type of treatment.


Chemotherapy is given together with surgery and/or radiotherapy to treat the tumour. The type of chemotherapy will vary in intensity and duration according to the stage of the tumour and its appearance under the microscope (histology).

Clinical trials

If your child takes part in a clinical trial, the treatment will be explained in more detail in the specific trial information sheet. You will be given an outline of the treatment in the form of a ‘road map’.

Effects of treatment

The prognosis for Wilms’ tumour is good for all children whatever their tumour stage, and most children are cured.

If the cancer comes back it is usually within the first two years. If this happens further treatment can be given. This may be more chemotherapy and could include surgery, radiotherapy and sometimes high-dose chemotherapy.

General side effects of chemotherapy

Bone marrow suppression (myelosuppression)

The bone marrow is where blood cells are produced (red blood cells, white blood cells and platelets). Chemotherapy drugs decrease the production of blood cells by the bone marrow for a variable period of time. White blood cells help the body to fight infection, platelets help to stop bleeding and bruising, and anaemia develops if red blood cells (or haemoglobin) are low. Your child may need blood or platelet transfusions and will be at increased risk of infections.

Nausea and vomiting

Some of the chemotherapy drugs used may make your child feel sick or vomit. Anti-sickness drugs given at the same time are usually very effective at stopping nausea and vomiting.

Sore mouth (mucositis)

Some of the chemotherapy drugs make the lining of the mouth and throat very sore and ulcerated. Your child will be given painkillers for this.

Hair loss

Temporary hair loss is common.

Long-term effects

When one kidney is removed the other kidney takes over the function of the missing kidney. If tumour has been removed from both kidneys then the remaining kidney tissue continues to function. Very few children have long-term kidney problems.

A small number of children develop side effects many years later because of the treatment they have received. These may include growth problems, reduced fertility, impaired heart and lung function and a small risk of developing a second cancer later in life.

About five years after treatment finishes your child’s care will be transferred to a long-term follow-up clinic. Your child will be seen at regular intervals in this clinic, indefinitely, to help with any long-term effects of the treatment.