How is it assessed?
Investigations are likely to include the following:
Blood tests
- Full blood count (FBC).
- Clotting studies (acquired von Willebrand disease affects up to 8% of children with Wilms tumour).
- Liver function.
- Urea and electrolytes (kidney function).
- Calcium.
Urine tests
- Microscopy and culture.
Imaging studies
These are very important and include:
- Ultrasound scan –may include ‘Doppler study’ a scan of the renal vein and inferior vena cava to see if there is tumour or tumour related clot in the main vein in the body or the renal vein that drains in to it from the kidney.
- Computed Tomography (CT) scan.
- Magnetic Resonance Imaging (MRI) scan.
CT and MRI are used to confirm that the tumour is within the kidney and not for example a neuroblastoma in the adjacent adrenal gland. These scans assess the extent of the spread of the tumour prior to surgery.
Tumour biopsy
Tumour biopsy is usually required to diagnose and stage Wilms tumour. This is often carried out even when the tumour cannot be completely removed. In the UK biopsy is done prior to chemotherapy.
Histology
This is the appearance of the cells from the tumour biopsy under the microscope. The appearance of the cells and other markers indicate how likely the tumour is to recur after treatment. A tumour with features associated with a low risk of recurrence is called ‘low risk’. In the medical evidence children may be referred to as ‘low risk’ or in the ‘low risk group’. These terms refer to the histology of the tumour they had and along with the spread of the tumour (the stage) is the most important determinant of how much treatment is required. Tumours may have characteristics that show a higher risk of recurrence after treatment, these are the ‘intermediate risk’ tumours and those with that show they are most likely to recur are called ‘high risk’.
Staging of Wilms tumour
Stage 1
35% of children will be stage 1:
- Tumour is confined to the kidney,
- The tumour has not broken through the layer around the kidney called the renal capsule.
Stage 2
15% of children:
- the tumour extends beyond the kidney or into blood vessels but is completely removed at surgery.
Stage 3
35% of children are in this group because one or more of the following is found during the operation to remove their tumour:
- the tumour is not completely removed at surgery,
- lymph nodes in the abdominal cavity contain tumour cells,
- tumour ruptures spilling tumour cells before or during surgery,
- tumour cells are found growing away from the tumour on the peritoneal lining of the abdominal cavity (peritoneal deposits or seedlings).
Stage 4
15% of children:
- Tumour cells have spread via the bloodstream to the lung, liver, bones or the brain and can be seen on CT or MRI scanning.
Stage 5
5% of children:
- Wilms tumour has developed in both kidneys ‘bilateral’ disease.
