7 Key Signs and Symptoms of Wilms Tumor in Children

Wilms tumor, also known as nephroblastoma, is a rare type of kidney cancer that primarily affects children, typically between the ages of 3 and 4 years old. It is the most common type of kidney cancer in children, accounting for about 90% of all childhood kidney cancers. Understanding the signs and symptoms of Wilms tumor is crucial for early detection and treatment, which significantly improves outcomes.

While Wilms tumor is relatively rare, affecting approximately 1 in 10,000 children, early recognition of symptoms can make a substantial difference in treatment success. The tumor usually affects only one kidney, though in rare cases (about 5-10%), it can occur in both kidneys simultaneously. Most children diagnosed with Wilms tumor are otherwise healthy and may not show obvious signs of illness until the tumor grows large enough to cause noticeable symptoms.

In this comprehensive guide, we’ll explore the seven most common symptoms of Wilms tumor, helping parents and caregivers recognize potential warning signs that warrant immediate medical attention.

1. Abdominal Swelling or Mass

The most common and often the first noticeable symptom of Wilms tumor is an abdominal swelling or a firm lump in the abdomen. This occurs in approximately 80-90% of children with Wilms tumor.

What to look for:

• A smooth, firm mass that can be felt in the abdomen, usually on one side
• Noticeable swelling or enlargement of the belly that increases over time
• The abdomen may appear asymmetrical, with one side looking larger than the other
• The mass is typically painless in early stages
• The swelling may be discovered accidentally during bathing or dressing

Parents often notice this symptom when giving their child a bath, changing clothes, or when the child’s clothes start fitting tighter around the waist. The mass can grow quite large before being detected, sometimes reaching the size of a softball or larger. Unlike normal abdominal bloating from gas or constipation, this swelling is persistent and progressively increases in size.

It’s important to note that the mass is usually firm and smooth to the touch, and in early stages, it typically doesn’t cause pain when pressed. This painless nature can sometimes delay diagnosis, as the child doesn’t complain of discomfort.

2. Abdominal Pain or Discomfort

While the tumor itself may not initially cause pain, as it grows, about 30-40% of children with Wilms tumor experience abdominal pain or discomfort.

Characteristics of the pain:

• Dull, persistent ache in the abdomen or side
• Pain may be intermittent or constant
• Discomfort may worsen with activity or movement
• The child may hold or protect their abdomen
• Pain can sometimes radiate to the back

The abdominal pain associated with Wilms tumor can vary in intensity. Some children may experience only mild discomfort that they might not even mention to their parents, while others may have more significant pain that interferes with daily activities. The pain typically occurs because the growing tumor stretches the kidney capsule or presses against surrounding organs and tissues.

In some cases, sudden severe abdominal pain can occur if the tumor bleeds internally or if the tumor ruptures. This is considered a medical emergency and requires immediate attention. Parents should be particularly alert if their child shows signs of acute abdominal pain combined with other symptoms like pallor, rapid heartbeat, or weakness.

3. Blood in the Urine (Hematuria)

Hematuria, or blood in the urine, is present in approximately 15-30% of children with Wilms tumor. This can be either visible to the naked eye (gross hematuria) or detected only through laboratory testing (microscopic hematuria).

What parents might notice:

• Pink, red, or cola-colored urine
• Blood clots in the urine (in more severe cases)
• Urine that appears cloudy or darker than normal
• The bleeding may be intermittent, coming and going

Blood in the urine occurs when the tumor invades the renal pelvis or the collecting system of the kidney, causing bleeding that mixes with urine. It’s important to understand that many conditions can cause blood in the urine, including urinary tract infections, kidney stones, or minor injuries, so this symptom alone doesn’t confirm Wilms tumor. However, any instance of blood in a child’s urine should be evaluated by a healthcare provider.

In cases of microscopic hematuria, the blood is not visible to the eye, and the condition may only be discovered during routine urine testing for other reasons. This is why regular pediatric check-ups that include urinalysis can be important for early detection.

4. High Blood Pressure (Hypertension)

Elevated blood pressure is found in approximately 25% of children diagnosed with Wilms tumor. This symptom is often discovered during a routine medical examination rather than through obvious signs.

How hypertension manifests:

• Usually asymptomatic and detected during blood pressure measurement
• In severe cases, may cause headaches
• Possible irritability or changes in behavior
• Rarely, may cause visual disturbances or nosebleeds
• Some children may appear flushed

The high blood pressure associated with Wilms tumor occurs because the tumor can produce excessive amounts of renin, a hormone that regulates blood pressure, or because the tumor compresses blood vessels leading to or from the kidney. Since children don’t typically have their blood pressure checked as routinely as adults, this symptom often goes unnoticed until a medical visit for other concerns.

Most young children cannot articulate symptoms of high blood pressure, which is why it’s often called a “silent” symptom. However, extremely high blood pressure can occasionally cause symptoms such as severe headaches, fatigue, confusion, or vision problems. Any of these symptoms, especially in combination with other signs of Wilms tumor, should prompt immediate medical evaluation.

5. Fever Without Infection

Unexplained fever occurs in approximately 15-20% of children with Wilms tumor. This fever is not related to any obvious infection and may persist or recur without a clear cause.

Fever characteristics:

• Low-grade fever that comes and goes
• Fever that doesn’t respond to typical fever treatments
• No accompanying signs of infection (no cough, runny nose, or sore throat)
• The child may feel warm to touch, especially in the evening
• Fever persists beyond what would be expected for a common childhood illness

Fever in Wilms tumor is considered a paraneoplastic symptom, meaning it’s caused by the body’s response to the tumor rather than by the tumor directly. The immune system recognizes the tumor cells as foreign and mounts a response that includes releasing fever-inducing substances. This type of fever is typically mild and may not make the child appear particularly sick, which can make it easy to overlook or attribute to common childhood illnesses.

Parents should be concerned if their child has recurrent fevers without an identifiable source of infection, especially if accompanied by other symptoms on this list. While fever is common in childhood and usually related to viral infections, persistent or recurrent unexplained fever warrants medical investigation.

6. Loss of Appetite and Weight Loss

Many children with Wilms tumor experience decreased appetite and subsequent weight loss. This occurs in approximately 15-20% of cases and may be one of the more subtle signs that parents notice over time.

Signs to watch for:

• Decreased interest in food, even favorite meals
• Eating smaller portions than usual
• Complaining of feeling full after eating very little
• Gradual or progressive weight loss
• Clothes becoming looser, especially around the waist (though the abdomen itself may be swollen)
• Lack of energy or enthusiasm for activities

Loss of appetite in Wilms tumor can occur for several reasons. The growing tumor may physically compress the stomach or intestines, creating a sensation of fullness. Additionally, the body’s metabolic response to cancer can alter appetite regulation. Some children may also experience nausea, which further reduces their desire to eat.

Weight loss in children is always a concern, as children are naturally growing and should be gaining weight over time. Even if a child maintains the same weight without gaining, this can be significant and may indicate an underlying problem. Parents who notice their child consistently refusing meals, showing disinterest in food, or losing weight should consult with a pediatrician, especially if these changes occur alongside other symptoms.

7. Fatigue and General Malaise

General tiredness, lack of energy, and overall malaise are common but non-specific symptoms that affect many children with Wilms tumor. While these symptoms can be attributed to many childhood conditions, their persistence should raise concern.

How this symptom presents:

• Unusual tiredness that doesn’t improve with rest
• Decreased interest in playing or participating in usual activities
• Appearing pale or looking generally unwell
• Needing more sleep than usual or taking frequent naps
• Lack of enthusiasm for activities they normally enjoy
• Difficulty keeping up with peers during physical activities

Fatigue in Wilms tumor can result from several factors. The tumor itself requires significant energy from the body as it grows. Additionally, if the tumor is affecting kidney function or causing anemia (from blood loss or decreased red blood cell production), this can contribute to feelings of exhaustion. The body’s immune response to the tumor also consumes energy, leaving the child feeling drained.

While fatigue is common in childhood for many benign reasons—such as growth spurts, busy schedules, or minor illnesses—persistent fatigue that doesn’t resolve and is accompanied by other symptoms should be evaluated by a healthcare provider. Parents know their children best and can often sense when tiredness is more than just the result of a busy day.

Main Causes of Wilms Tumor

While the exact cause of Wilms tumor is not fully understood, research has identified several factors that contribute to its development:

Genetic Mutations: Wilms tumor develops when certain genes that control normal kidney cell growth become mutated. These mutations can occur spontaneously during fetal development or can be inherited. Several genes have been associated with Wilms tumor, including WT1, WT2, and several others. These genetic changes cause kidney cells to continue growing and dividing uncontrollably instead of maturing into normal kidney tissue.

Abnormal Kidney Development: During fetal development, some kidney cells called nephrogenic rests may fail to mature properly. These immature cells can sometimes develop into Wilms tumor after birth. Approximately 25-40% of Wilms tumors are associated with nephrogenic rests.

Associated Genetic Syndromes: Certain genetic conditions increase the risk of developing Wilms tumor:

• WAGR syndrome: A rare genetic disorder characterized by Wilms tumor, Aniridia (absence of the iris), Genitourinary abnormalities, and intellectual disability (Range of developmental delays)
• Denys-Drash syndrome: A condition affecting kidney function and genital development
• Beckwith-Wiedemann syndrome: An overgrowth disorder that increases cancer risk
• Hemihypertrophy: A condition where one side of the body grows larger than the other

Family History: While most cases of Wilms tumor occur sporadically with no family history, approximately 1-2% of children with Wilms tumor have a family member who has also had the disease. When there is a family history, children may develop the tumor at a younger age or may have tumors in both kidneys.

Congenital Anomalies: Children born with certain birth defects, particularly those affecting the genitourinary system, have an increased risk of developing Wilms tumor. These include absence of the iris (aniridia), undescended testicles, hypospadias, and certain kidney abnormalities.

It’s important to note that in most cases, Wilms tumor occurs in children with no known risk factors or genetic syndromes. The mutations that lead to Wilms tumor typically occur randomly during early development, and there is nothing parents could have done to prevent them.

Prevention

Unfortunately, there are no known methods to prevent Wilms tumor because it typically results from genetic mutations that occur randomly during fetal development. Unlike some cancers in adults that can be prevented through lifestyle modifications, Wilms tumor is not associated with environmental factors, diet, or lifestyle choices.

However, there are important steps that can be taken for early detection, particularly in high-risk children:

Screening for High-Risk Children: Children with genetic syndromes or family history of Wilms tumor should undergo regular screening. This typically involves:

• Regular abdominal ultrasounds every 3-4 months until age 7-8
• Physical examinations to check for abdominal masses
• Blood pressure monitoring
• Urinalysis to check for blood in urine

Genetic Counseling: Families with a history of Wilms tumor or associated genetic syndromes should consider genetic counseling. This can help identify children at higher risk who would benefit from surveillance programs and can provide information about the likelihood of recurrence in future children.

Awareness and Early Detection: While prevention isn’t possible, early detection significantly improves outcomes. Parents and caregivers should:

• Be aware of the signs and symptoms of Wilms tumor
• Perform regular abdominal checks during bathing, especially in children with risk factors
• Ensure children attend regular pediatric check-ups
• Report any concerning symptoms to a healthcare provider promptly

The good news is that Wilms tumor has an excellent prognosis when detected and treated early. The overall survival rate exceeds 90%, with even higher rates for tumors detected at early stages. This makes awareness of symptoms and prompt medical attention crucial components of managing this condition, even though prevention is not possible.

Frequently Asked Questions

What age group is most commonly affected by Wilms tumor?

Wilms tumor most commonly affects children between the ages of 3 and 4 years old. About 75% of cases are diagnosed before age 5, and it is rarely diagnosed in children older than 10 years or in adults. The median age at diagnosis is approximately 3.5 years.

Can Wilms tumor occur in both kidneys?

Yes, although uncommon, Wilms tumor can occur in both kidneys (bilateral) in about 5-10% of cases. Bilateral tumors are more common in children with certain genetic syndromes and may require different treatment approaches. Children with genetic conditions associated with Wilms tumor have a higher risk of developing tumors in both kidneys.

Is Wilms tumor hereditary?

Most cases of Wilms tumor are not hereditary and occur sporadically. However, approximately 1-2% of cases have a family history of the disease. Children with certain inherited genetic syndromes, such as WAGR syndrome or Beckwith-Wiedemann syndrome, have an increased risk of developing Wilms tumor.

How quickly does Wilms tumor grow?

Wilms tumor can grow relatively quickly. The tumor may double in size within weeks to months. This is why a mass that wasn’t noticeable a few weeks ago might suddenly become apparent. The rapid growth rate makes prompt medical evaluation important when symptoms are noticed.

Can Wilms tumor spread to other parts of the body?

Yes, Wilms tumor can spread (metastasize) to other parts of the body, most commonly to the lungs and liver. Approximately 10-15% of children have detectable metastases at the time of diagnosis. This is why comprehensive evaluation and staging are important once Wilms tumor is suspected.

What is the difference between Wilms tumor and other kidney problems in children?

Wilms tumor is a cancerous growth of kidney cells, while many other kidney problems in children are related to infections, congenital abnormalities, or functional issues. Unlike kidney infections or stones which often cause acute symptoms like fever and severe pain, Wilms tumor symptoms develop more gradually and often include a noticeable abdominal mass as the primary sign.

Should I be worried if my child has one of these symptoms?

While any of these symptoms warrant medical attention, having one symptom doesn’t necessarily mean your child has Wilms tumor. Many of these symptoms can be caused by common, benign conditions. However, if your child has multiple symptoms, particularly an abdominal mass or swelling, you should seek medical evaluation promptly. Early detection is key to successful outcomes.

How is Wilms tumor diagnosed?

Diagnosis typically involves several steps including physical examination, imaging studies (ultrasound, CT scan, or MRI), and blood and urine tests. If imaging suggests a tumor, additional tests may be performed to determine if the cancer has spread. A definitive diagnosis is usually made through imaging combined with surgical removal and examination of the tumor tissue, though biopsy before surgery is generally avoided to prevent tumor spread.

What should I do if I notice a lump in my child’s abdomen?

If you notice a lump or mass in your child’s abdomen, contact your pediatrician immediately. While it may not be Wilms tumor, any unexplained abdominal mass in a child requires prompt medical evaluation. Your doctor will perform a physical examination and likely order imaging tests to determine the nature of the mass.

References:

• American Cancer Society – Wilms Tumor
• National Cancer Institute – Wilms Tumor Treatment
• Mayo Clinic – Wilms Tumor
• Boston Children’s Hospital – Wilms Tumor
• St. Jude Children’s Research Hospital – Wilms Tumor