Wilms' tumour

A Wilms' tumour is a type of kidney cancer, named after Dr Max Wilms who first wrote a paper about this condition in 1899.  It can also be called a nephroblastoma.

The kidneys

The kidneys are two organs that are found at the back of the abdomen. They are responsible for cleaning the blood to remove excess fluids and waste products which are then converted to urine.

A Wilms’ tumour may begin to develop in the kidneys when a baby is still inside the womb, if the cells which should have gone on to be kidney cells remain immature. If these cells do not mature they can grow to form a Wilms' tumour.

Wilms’ tumours usually only affect one kidney, but in about 7% of cases it affects both.

Who does it affect?

Wilms' tumours usually affect children under the age of five. Some children may be more at risk of developing a Wilms' tumour because other family members have been affected. In other cases, the tumour can be linked to other developmental issues that have been present since birth.

What are the symptoms?
How is it diagnosed?
How is it treated?
What are the treatment side-effects?
After treatment

What are the symptoms?

The most common symptom of a Wilms' tumour is a swollen stomach. This can occur quite suddenly and is usually painless to your child. Other symptoms may include raised blood pressure, blood in the urine, constipation and a loss of appetite.

How is it diagnosed?

The diagnosis of Wilms' tumours usually involves a biopsy. This is where a sample of the tissue will be taken and examined under a microscope. Urine samples will be taken to check how your child’s kidneys are functioning and ultrasound or CT scans will be used to see whether the cancer has spread.

How is it treated?

The treatment of a Wilms' tumour will depend on its size, whether or not it has spread to other parts of the body and the type of cells involved. In some cases, specialists discover anaplasia cells during their diagnosis tests. These are large cells that do not look like kidney cells. The presence of anaplasia will require a stronger treatment because these tumours are more difficult to treat.


If possible, the tumour will be removed by surgery. This may involve removing part of or the entire kidney. Your child’s surgeon will aim to keep as much of the healthy kidney as possible. If Wilms’ tumours are in both kidneys then each kidney will be operated on separately.

Chemotherapy and radiotherapy

Chemotherapy involves using anti-cancer drugs to target the cancer cells. In the UK it is usually given before surgery to shrink the tumour and then after surgery to stop the cancer from returning.

Radiotherapy may also be given, depending on the stage of the tumour. This involves targeting the tumour with high-energy rays.

What are the treatment side-effects?

If your child is undergoing chemotherapy, he or she may experience side-effects such as tiredness, sickness, diarrhoea and temporary hair loss. Your child may also be at greater risk of infections. Radiotherapy can also make your child feel tired and sick. He or she might experience skin irritation similar to sun burn and hair loss in the area that is being treated. Talk to your specialist or nurses about how you can manage these side-effects, or see the side-effects section of our website for more information.

After treatment

Follow up

After your child's treatment is complete they will still need to be seen regularly at an outpatient clinic. At this clinic, your child’s specialist will be looking for any signs that the cancer has returned (this is known as a relapse). They will also check that your child’s major organs, such as the heart and lungs, are still functioning correctly and haven’t been affected by the cancer treatment.

Long-term follow up

Once your child’s risk of relapse has reduced, the focus of on-going follow up changes to looking out for potential long term side effects of treatment. The risk of long term side effects depends on the type of cancer your child had and the treatment received. A personalised surveillance plan is usually created that outlines the specific long term follow up and on-going investigations that your child will require. Many people are at low risk of future health problems but some will have significant on-going health needs. Talk to your child’s specialist about the potential long-term side-effects of their treatment.

Long-term side-effects

When one kidney has been removed, the other will still function normally and will take over the work of the kidney that has been removed. Because Wilms’ tumours usually occur in one kidney only, very few children go on to have long-term kidney problems.

Updated January 2015, next planned review 2017.