Diagnosis of Wilms tumour

Diagnosis is the process of finding out the cause of a health problem. Diagnosing Wilms tumour usually begins with a visit to your child’s doctor. The doctor will ask you about any symptoms your child has and do a physical exam. Based on this information, the doctor may refer you to a specialist or order tests to check for Wilms tumour or other health problems.

It’s important for the healthcare team to rule out other reasons for a health problem before making a diagnosis of Wilms tumour. If the doctor suspects Wilms tumour, your child’s care will be managed by a healthcare team that specializes in caring for children with cancer. All cases of childhood kidney tumours are considered urgent.

The following tests are usually used to rule out or diagnose Wilms tumour. Many of the same tests used to diagnose cancer are used to find out the stage (how far the cancer has spread). The doctor may also order other tests to check your child’s general health and to help plan their treatment.

Health history and physical exam

Your child’s health history is a record of their symptoms, risk factors and past medical events and problems. The doctor will ask questions about your child’s personal or family history of certain genetic conditions and congenital abnormalities such as:

  • a family history of Wilms tumour
  • WAGR syndrome
  • Beckwith-Wiedemann syndrome
  • Denys-Drash syndrome
  • Simpson-Golabi-Behmel syndrome
  • Perlman syndrome
  • Frasier syndrome
  • Bloom syndrome
  • aniridia(the iris of the eye has not developed)
  • hemihypertrophy (one side of the body is bigger than the other)
  • undescended testicles
  • hypospadias (the urinary opening is on the underside of the penis rather than at the tip)

A physical exam allows the doctor to look for any signs of Wilms tumour. During a physical exam, the doctor may feel your child’s abdomen for any lumps or swelling. As kidney tumours are sometimes fragile, it is important that the number of healthcare providers feeling the lump is limited.

Find out more about physical exams.


Urinalysis is a test that measures substances in urine. These substances include electrolytes, hormones and other waste products of the metabolism.

Urinalysis can be used to check for blood in your urine, which you might not be able to see. If there is blood, it means that there is bleeding into or within the kidneys or urinary tract. This bleeding can be a sign of kidney cancer.

Find out more about urinalysis.

Urine cytology

A urine cytology test looks for abnormal cells in the urine. The doctor may order this test if urinalysis finds blood in your child’s urine. It is not usually used to make a diagnosis of Wilms tumour.

Find out more about cell and tissue studies, including cytology.

Complete blood count (CBC)

A CBC measures the number and quality of white blood cells, red blood cells and platelets. A CBC is done to check for anemia, which is a low number of red blood cells. It is also important to know that the blood is normal before starting chemotherapy.

Find out more about a complete blood count.

Blood chemistry tests

Blood chemistry tests measure certain chemicals in the blood. They show how well certain organs are functioning and can help find abnormalities. Blood chemistry tests that may be done include the following.

Blood urea nitrogen (BUN) and creatinine may be measured to check how well the kidneys are working. Higher levels of these substances may mean that the kidneys are not functioning well, which may be because of cancer.

Glomerular filtration rate (GFR) is another test used to check how well the kidneys are working. It measures how much blood is passing through the glomeruli, which are the tiny filters in the kidney that remove waste from the blood. The creatinine level is combined with several other factors, such as age, sex, height, weight and ethnicity, to estimate the GFR. Low levels of GFR may be a sign of chronic kidney disease. Very high levels are a sign that the kidneys are failing, which needs to be treated immediately.

Calcium and phosphorus levels may be high if you have kidney disease or if cancer has spread to the bone.

Alkaline phosphatase levels may be high if kidney cancer has spread to the bones or liver.

Liver function tests may be done to see if there are any problems with the liver. Some chemotherapy drugs can only be given if the liver is working well.

Find out more about blood chemistry tests.


An ultrasound uses high-frequency sound waves to make images of parts of the body. It is used to look at the kidneys and surrounding tissues and organs.

An abdominal ultrasound is often the first imaging test done if the doctor suspects Wilms tumour because it is a painless procedure and it allows the doctor to see the whole abdomen.

Find out more about ultrasounds.


An x-ray uses small doses of radiation to make an image of parts of the body on film. A chest x-ray may be done to check if the cancer has spread to the lungs.

Find out more about x-rays.

CT scan

A computed tomography (CT) scan uses special x-ray equipment to make 3D and cross-sectional images of organs, tissues, bones and blood vessels inside the body. A computer turns the images into detailed pictures.

An abdominal CT scan is used to look at the kidneys. A CT scan is also useful for checking whether cancer has spread to other organs or tissues, such as blood vessels, the other kidney or the lungs.

Find out more about CT scans.


Magnetic resonance imaging (MRI) uses powerful magnetic forces and radiofrequency waves to make cross-sectional images of organs, tissues, bones and blood vessels.

An abdominal MRI is used to show more detailed images of the kidneys, including the major blood vessels nearby. An MRI can also be used to check if the cancer has spread to the other kidney or the brain.

In most cases the doctor will use either a CT scan or an MRI (rather than both) to show pictures of the abdomen.

Find out more about MRIs.

PET scan

A positron emission tomography (PET) scan uses radioactive materials called radiopharmaceuticals to look for changes in the metabolic activity of body tissues. A computer analyzes the radioactive patterns and makes 3D colour images of the area being scanned.

In most children with kidney tumours, a PET scan isn’t usually one of the initial tests. PET scans may be useful to look at the response of tumours to chemotherapy, but most doctors rely on CT scans or MRIs to detect changes in the size of the tumours. If a PET scan is used, it is typically combined with a CT scan for a more complete picture.

PET scans may not be available in all cancer treatment centres. Find out more about PET scans.


In most cases of Wilms tumour, it is best to remove the primary tumour without doing a biopsy first. The most common surgery used is a nephrectomy, which removes the tumour and the kidney. This surgery allows doctors to determine the stage of the cancer. The surgeon will also take tissue samples from nearby lymph nodes to stage the cancer and determine the best treatments to give after surgery.

A biopsy of the tumour will be done instead of surgery only if:

  • the tumour cannot be removed safely
  • the child only has one kidney
  • there are tumours in both kidneys
  • the child appears to have a condition that puts them at risk of a second Wilms tumour
  • the imaging brings into strong question whether the abnormality is really a tumour or not

Samples collected during surgery or biopsy are tested in a lab. A report from the pathologist will show whether or not cancer cells are found in the sample.

Find out more about surgery for Wilms tumour and biopsy.

Chromosome tests

Tumour tissue removed during surgery may be tested for changes in chromosomes. A variety of chromosomal changes have been associated with Wilms tumour. These changes can cause a tumour to have a different response to treatment. For example, a tumour with changes in chromosomes 1 and 16 may not respond as well to standard treatment and may need more chemotherapy.

Questions to ask your healthcare team

Find out more about helping your child cope with tests and treatment. To make the decisions that are right for your child, ask the healthcare team questions about a diagnosis.

Expert review and references

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