What is Wilms tumor?
Wilms tumor (nephroblastoma) is a malignant tumor of the kidney. It is an embryonal tumor linked to a disturbance in how the kidney develops before birth. More than 80% of kidney tumors in children are Wilms tumors. Overall, it is a rare disease.
It is most common in children aged 2–5 years. Usually one kidney is affected; in about 5–9% of children the tumor is found in both kidneys.
The most important message: with modern treatment more than 90% of children are cured.
What do parents notice?
- Most children have no complaints at all. Parents often notice by chance that the belly has got bigger or that there is a firm lump in it, while dressing or cuddling their child.
- About 1 in 5 children also have other signs: belly pain, blood in the urine, fever, high blood pressure.
A child who feels well does not mean the lump is harmless.
What should we do?
If you notice a new lump in your child’s belly or one side of the belly getting bigger:
- have your child seen by a doctor without delay, as soon as possible,
- if the lump comes with severe belly pain or blood in the urine, go straight to the emergency department.
A child with suspected Wilms tumor should be examined and treated at a pediatric oncology center. There a team of doctors and nurses experienced in this disease works together.
Diagnosis
- Abdominal ultrasound: the first and most widely available test. It shows whether the lump is coming from the kidney. More: kidney and bladder ultrasound.
- CT or MRI: done before treatment to assess the size and spread of the tumor and the other kidney precisely.
- Blood and urine tests, and blood pressure measurement.
Treatment
Treatment combines chemotherapy and surgery, and in some cases radiotherapy. The order of treatment can differ between countries and centers: some give chemotherapy first and then operate, others operate first. The pediatric oncology team decides which path to take and how long treatment will last, based on the type and stage of the tumor.
Who is at higher risk?
Wilms tumor is more common in children with certain congenital syndromes, for example Beckwith-Wiedemann syndrome, WAGR and Denys-Drash syndromes, or when one side of the body is larger than the other (hemihypertrophy). These children are usually offered a belly ultrasound every 3 months until about 7 years of age.
After treatment
Most children with Wilms tumor are cured. But treatment can affect health even years later: some survivors develop chronic health problems in adulthood. That is why long-term follow-up after treatment matters. About living with one kidney: solitary kidney.
When to seek urgent care
If any of the following is present, do not wait for a routine appointment: call the doctor or go to the nearest emergency department.
- A lump in the belly together with severe belly pain
- Visible blood in the urine
Call your local emergency number (112 in Europe, 911 in North America)
Note for pediatricians and family doctors
Malignant renal tumors make up 5% of all cancers before the age of 15 years; Wilms tumor accounts for more than 80% of pediatric renal tumors. Age at presentation is typically 2–5 years; about 7% are multicentric and 5–9% bilateral. Most children are asymptomatic at presentation, with a distended abdomen and a palpable mass; parents frequently notice the mass while dressing or cuddling the child. Only about one in five children have distinct symptoms, such as pain, hematuria, fever or hypertension. Abdominal ultrasound is the first investigation; in better-resourced settings CT or MRI is done before surgery. SIOP favors neoadjuvant chemotherapy followed by resection and adjuvant therapy, whereas COG recommends primary nephrectomy for unilateral renal masses; treatment combines chemotherapy, surgery and, in some cases, radiotherapy. Overall survival exceeds 90%, yet about 25% of survivors report severe chronic health conditions in adult life. Children with WT1-related syndromes (for example WAGR, Denys-Drash), Beckwith-Wiedemann syndrome or isolated hemihypertrophy are offered ultrasound screening every three months until about seven years of age. A child with a suspected renal mass should be referred without delay to a pediatric oncology center; participation of all children with renal tumors in clinical trials is recommended.
What happens at the visit?
- The belly is examined carefully, an ultrasound of the kidneys and abdomen is done, and blood pressure is measured.
- If a kidney tumor is suspected, the child is referred without delay to a pediatric oncology center.
- We explain the next steps and tests to the parents, and when needed we take part in urological follow-up after treatment.
Frequently asked questions
I felt a lump in my child's belly, but they seem well. Can we wait?
No. Most children with Wilms tumor feel well and have no other complaints. If you notice a new lump or one side of the belly getting bigger, have your child seen by a doctor as soon as possible.
My child has Beckwith-Wiedemann syndrome (or one side of the body is larger). What should we do?
Some syndromes carry a higher risk of Wilms tumor. These children are usually offered a belly ultrasound every 3 months until about 7 years of age. Discuss the plan with your doctor.
What happens after treatment?
Most children are cured. But treatment can affect health years later, so long-term follow-up arranged by the pediatric oncology center is needed.
Related topics
- Hydronephrosis Water on the kidney, dilated renal pelvis Condition
- Multicystic dysplastic kidney Cystic, non-functioning kidney Condition
- Blood in urine Hematuria, red or brown urine Condition
- Solitary kidney Single kidney, born with one kidney Condition
- Kidney and bladder ultrasound Ultrasound scan, sonography Test
Sources
- Spreafico F et al. Wilms tumour. Nat Rev Dis Primers, 2021.
This information is for educational purposes and does not replace medical advice. Decisions about your child’s treatment are made with the doctor after an examination.
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