Wilms Tumor: Childhood Kidney Cancer Symptoms & Treatment

What Is Wilms Tumor?

Wilms tumor (nephroblastoma) is a rare kidney cancer that primarily affects children under 5 years of age. It accounts for about 5% of all childhood cancers and is the most common kidney tumor in children. With current treatment protocols, approximately 90% of children with Wilms tumor are cured.

Wilms tumor, also known as nephroblastoma, is a malignant tumor that develops in the kidney tissue of young children. The tumor typically arises from cells that were supposed to develop into normal kidney tissue during fetal development but instead remained in an immature state and later began to grow uncontrollably. This is why Wilms tumor is sometimes called an "embryonal" tumor - it develops from cells that resemble those found in developing embryos.

The condition was named after Max Wilms, a German surgeon who first described the tumor in detail in 1899. Since then, tremendous advances in understanding and treating this cancer have transformed it from a nearly always fatal disease to one of the most curable childhood cancers. The development of standardized treatment protocols by organizations like the Children's Oncology Group (COG) in North America and the International Society of Paediatric Oncology (SIOP) in Europe has been instrumental in achieving these remarkable outcomes.

Wilms tumor usually develops in only one kidney (unilateral), but in approximately 5-10% of cases, it affects both kidneys (bilateral). Bilateral tumors are more common in younger children and in those with certain genetic syndromes. Importantly, the presence of tumor in both kidneys does not necessarily indicate a worse prognosis, though it does require more complex treatment planning to preserve as much kidney function as possible.

Epidemiology and Risk Factors

Wilms tumor affects approximately 1 in 10,000 children worldwide, making it relatively rare. In terms of childhood cancers, it represents about 5% of all pediatric malignancies. The tumor has a peak incidence between ages 3-4 years, with the majority of cases diagnosed before age 5. It is extremely rare in children over 10 years old and adults.

Several factors may influence the risk of developing Wilms tumor:

• Gender: Girls are slightly more likely to develop Wilms tumor than boys
• Race: African-American children have slightly higher rates than white children, while Asian children have lower rates
• Family history: About 1-2% of Wilms tumor cases run in families
• Genetic syndromes: Children with certain syndromes have significantly increased risk
• Birth defects: Certain physical abnormalities present at birth are associated with higher risk

Associated Genetic Syndromes

While most cases of Wilms tumor occur sporadically without any identifiable cause, certain genetic syndromes are associated with increased risk. Children with these conditions are typically monitored closely with regular ultrasound screening:

What Are the Symptoms of Wilms Tumor?

The most common symptom of Wilms tumor is a painless abdominal mass or swelling that parents often notice when bathing or dressing their child. Other symptoms can include abdominal pain, blood in the urine, fever, high blood pressure, and loss of appetite. Many children show no symptoms initially.

Wilms tumor often grows to a considerable size before causing any symptoms, which is why it may be quite large when first discovered. Unlike many adult cancers, the size of the tumor at diagnosis does not necessarily correlate with prognosis - even large tumors that haven't spread outside the kidney have excellent cure rates. Understanding the potential symptoms helps parents and healthcare providers recognize the condition early.

The presentation of Wilms tumor can vary considerably from child to child. Some tumors are discovered incidentally during a routine well-child examination when a doctor feels an abdominal mass. Others come to attention because parents notice something unusual about their child's abdomen. In some cases, the tumor is found during imaging studies performed for unrelated reasons.

Abdominal Mass or Swelling

The most characteristic sign of Wilms tumor is a mass in the abdomen. Parents often describe first noticing a lump, swelling, or bulging on one side of their child's belly. This mass is typically firm, smooth, and does not move around when touched. Most importantly, it is usually painless - the child typically does not complain of discomfort when the area is touched or pressed.

The abdominal swelling associated with Wilms tumor can develop gradually over weeks to months. Parents might notice that their child's pants or diapers no longer fit properly, or that one side of the abdomen appears larger than the other. The mass may become more noticeable after the child eats, as a full stomach can push the tumor forward and make it more prominent.

Other Common Symptoms

While the abdominal mass is the hallmark symptom, children with Wilms tumor may experience various other symptoms:

• Abdominal pain: Although the mass itself is usually painless, some children experience vague abdominal discomfort or pain. This may occur if the tumor grows large enough to press on surrounding structures or if there is bleeding within the tumor.
• Blood in urine (hematuria): Approximately 25% of children with Wilms tumor have blood in their urine. Sometimes this is visible to the naked eye (gross hematuria), appearing pink, red, or cola-colored. Other times, it can only be detected through laboratory testing (microscopic hematuria).
• High blood pressure (hypertension): Up to 25% of children with Wilms tumor develop high blood pressure due to the tumor producing a hormone called renin or compressing the blood vessels of the kidney.
• Fever: Some children develop unexplained fever that persists or recurs without an obvious infection.
• Loss of appetite and weight loss: As with many cancers, children may experience decreased appetite and unintentional weight loss.
• Constipation: A large tumor can press on the intestines and cause changes in bowel habits.
• General malaise: Children may appear tired, irritable, or "not themselves."

Symptoms in Advanced Disease

If Wilms tumor has spread beyond the kidney at the time of diagnosis, additional symptoms may be present. The lungs are the most common site of metastasis (spread), occurring in about 10-15% of cases at diagnosis. Children with lung involvement may experience shortness of breath, cough, or chest discomfort. However, many children with lung metastases have no respiratory symptoms at all, and the spread is only detected through imaging studies.

How Is Wilms Tumor Diagnosed?

Diagnosis of Wilms tumor begins with a physical examination and is confirmed through imaging tests including ultrasound, CT scan, and chest imaging. Unlike many adult cancers, a biopsy is typically not performed before treatment begins, as the diagnosis can usually be made with imaging studies alone.

The diagnostic process for Wilms tumor is designed to confirm the presence of a kidney tumor, determine whether it has spread, and assess the child's overall health in preparation for treatment. The approach is multidisciplinary, involving pediatric oncologists, surgeons, radiologists, and other specialists working together to develop an optimal treatment plan.

When a child presents with symptoms suggestive of Wilms tumor, the diagnostic workup typically proceeds rapidly. Healthcare providers understand the anxiety that parents experience during this time and work to complete the necessary tests as efficiently as possible while ensuring thorough evaluation.

Physical Examination

The initial evaluation begins with a careful physical examination. The doctor will gently feel (palpate) the child's abdomen to assess for masses. It's important to be gentle during this examination because vigorous palpation could theoretically cause tumor rupture, though this is rare. The doctor will also check blood pressure, look for signs of associated syndromes, and assess the child's overall condition.

Imaging Studies

Imaging is essential for diagnosis and staging of Wilms tumor. Several different imaging modalities are typically used:

Abdominal Ultrasound: This is usually the first imaging test performed because it is quick, non-invasive, does not require radiation, and does not need sedation in most children. Ultrasound can effectively show the presence of a kidney mass and help distinguish solid tumors from fluid-filled cysts. It can also show whether one or both kidneys are affected and whether there is tumor extension into the renal vein or inferior vena cava.

CT Scan (Computed Tomography): A CT scan of the abdomen and pelvis provides more detailed information about the tumor's size, location, and relationship to surrounding structures. It shows whether the tumor appears confined to the kidney or has invaded nearby tissues. CT is also useful for evaluating lymph nodes in the abdomen and checking the opposite kidney carefully.

MRI (Magnetic Resonance Imaging): In some centers, MRI is used instead of or in addition to CT. MRI provides excellent soft tissue detail without radiation exposure. It is particularly useful for evaluating tumor extension into blood vessels and for imaging bilateral tumors where preservation of kidney tissue is important.

Chest Imaging: Because the lungs are the most common site of metastasis, all children undergo chest imaging. This typically includes a chest X-ray and/or CT scan of the chest. Lung metastases appear as small round nodules on imaging.

Laboratory Tests

Blood and urine tests help assess the child's overall health and kidney function:

• Complete blood count: To check for anemia and assess blood cell counts before treatment
• Kidney function tests: To evaluate how well both kidneys are working
• Liver function tests: To check liver health before chemotherapy
• Urinalysis: To look for blood or abnormal cells in the urine
• Coagulation studies: To ensure blood clots normally before surgery

Staging

Staging describes the extent of the cancer and is crucial for determining treatment. The staging system for Wilms tumor considers whether the tumor is confined to the kidney, has spread to nearby structures or lymph nodes, or has metastasized to distant sites like the lungs:

How Is Wilms Tumor Treated?

Treatment for Wilms tumor typically involves a combination of chemotherapy, surgery (nephrectomy), and sometimes radiation therapy. Most children receive chemotherapy first to shrink the tumor, followed by surgical removal of the affected kidney, and then additional chemotherapy. The specific treatment plan depends on the tumor stage and histology.

The treatment of Wilms tumor represents one of the greatest success stories in pediatric oncology. Over the past several decades, coordinated efforts by researchers and clinicians have developed highly effective treatment protocols that have transformed outcomes for children with this cancer. Today, the overall survival rate exceeds 90%, and even children with advanced disease have good chances of cure.

Treatment approaches differ somewhat between North America (following Children's Oncology Group protocols) and Europe (following SIOP protocols), but both achieve excellent results. The main difference is timing: in North America, surgery is typically performed first, while in Europe, chemotherapy is given before surgery to shrink the tumor and make surgical removal safer and easier.

Chemotherapy

Chemotherapy uses medications to kill cancer cells and is a cornerstone of Wilms tumor treatment. The specific drugs used and the duration of treatment depend on the tumor stage and histology (how the cells look under the microscope).

Pre-operative (Neoadjuvant) Chemotherapy: In the SIOP approach used in many countries, children receive chemotherapy for 4-6 weeks before surgery. This serves several purposes: it shrinks the tumor, making surgical removal safer; it reduces the risk of tumor rupture during surgery; and it allows doctors to assess how the tumor responds to treatment, which provides valuable prognostic information.

Post-operative (Adjuvant) Chemotherapy: After surgery, most children receive additional chemotherapy to eliminate any remaining cancer cells and reduce the risk of recurrence. The duration varies based on staging and tumor characteristics:

• Stage I with favorable histology: May receive as few as 4 weeks of chemotherapy with two drugs
• Stage II-III with favorable histology: Typically 6-7 months of chemotherapy
• Stage IV or unfavorable histology: More intensive chemotherapy for 6-12 months

The most commonly used chemotherapy drugs for Wilms tumor include vincristine, actinomycin D (dactinomycin), and doxorubicin. These drugs are generally well-tolerated, though they can cause side effects including nausea, hair loss, decreased blood counts, and mouth sores. The medical team closely monitors children during treatment and provides supportive care to manage side effects.

Surgery

Surgery is essential for treating Wilms tumor and involves removing the affected kidney (nephrectomy) along with the tumor. The surgeon also removes nearby lymph nodes to check for cancer spread and carefully examines the abdomen for any signs of tumor extension.

Radical Nephrectomy: The standard surgical procedure involves removing the entire kidney containing the tumor along with surrounding fatty tissue and the adrenal gland (if attached to the tumor). This is the most common approach when only one kidney is affected and the other kidney is healthy.

Nephron-Sparing Surgery: When both kidneys are affected (bilateral disease), surgeons try to preserve as much healthy kidney tissue as possible. This may involve removing tumors from both kidneys while leaving functioning kidney tissue in place. This approach requires careful planning and expertise in pediatric urology.

Surgery is typically performed through a traditional open incision that provides the surgeon with good visualization and access. In carefully selected cases, minimally invasive (laparoscopic or robotic) approaches may be considered, though these are less commonly used for Wilms tumor than for some other conditions.

Radiation Therapy

Radiation therapy uses high-energy beams to kill cancer cells and may be recommended in certain situations:

• Stage III disease: When there is residual tumor in the abdomen or involvement of lymph nodes
• Stage IV with lung metastases: Whole lung radiation may be given if lung nodules don't completely respond to chemotherapy
• Unfavorable histology: More aggressive tumor types often require radiation
• Tumor spillage: If the tumor ruptured during surgery, radiation to the abdomen may be recommended

Modern radiation techniques are carefully designed to minimize exposure to healthy tissues. Treatment is typically given daily over 1-2 weeks. Children usually tolerate radiation well, though some may experience temporary fatigue, skin changes, or digestive symptoms.

Treatment for Bilateral Wilms Tumor

When both kidneys are affected, the treatment approach focuses on eliminating cancer while preserving as much kidney function as possible. This typically involves:

• Extended pre-operative chemotherapy to shrink tumors in both kidneys
• Careful surgical planning, often using nephron-sparing techniques
• Sometimes staged surgeries on each kidney at different times
• Close monitoring of kidney function throughout treatment

What Is Life Like After Wilms Tumor Treatment?

Most children recover well after Wilms tumor treatment and live normal, healthy lives. Children can function normally with one kidney, which grows larger to compensate. Long-term follow-up is important to monitor for any late effects of treatment and ensure the remaining kidney stays healthy.

Completing treatment for Wilms tumor marks the beginning of an important new phase: survivorship. The vast majority of children who complete treatment are cured and go on to live full, active lives. However, the journey doesn't end with the last treatment session - ongoing follow-up care is essential to monitor for any late effects of treatment and ensure optimal long-term health.

Living with One Kidney

Most children who have a nephrectomy for Wilms tumor adapt remarkably well to life with a single kidney. The remaining kidney undergoes a process called compensatory hypertrophy, where it grows larger and increases its filtration capacity to compensate for the removed kidney. Within months of surgery, the remaining kidney typically handles 70-80% of the normal two-kidney function.

For most activities and life choices, having one kidney makes little practical difference. Children can participate fully in sports, including contact sports (though some doctors recommend protecting the remaining kidney with appropriate padding), and there are no significant dietary restrictions. As they grow into adults, they can pursue any career and, for women, pregnancy is generally safe with proper monitoring.

There are a few considerations for living with one kidney:

• Stay hydrated: Drinking adequate water supports kidney function
• Blood pressure monitoring: Regular blood pressure checks help detect any kidney-related issues early
• Medication caution: Some over-the-counter pain medications (NSAIDs) should be used sparingly as they can affect kidney function
• Healthy lifestyle: Maintaining healthy weight and blood pressure protects the remaining kidney
• Medical alert: Informing healthcare providers about having one kidney ensures appropriate care

Long-Term Follow-Up

Children who have completed treatment for Wilms tumor require regular follow-up visits for several years, and in some cases, throughout life. The purposes of this monitoring include:

Recurrence Surveillance: Although most relapses occur within the first two years after treatment, monitoring continues for longer. Follow-up typically includes regular physical examinations, imaging studies (ultrasound, chest X-ray), and laboratory tests. The frequency of visits decreases over time as the risk of recurrence diminishes.

Late Effects Monitoring: Treatment for Wilms tumor can sometimes cause health problems that appear years later. The risk and type of late effects depend on the specific treatments received:

• Kidney function: Regular monitoring of kidney function is important, especially for children who received certain chemotherapy drugs or had bilateral disease
• Heart health: Doxorubicin, used in some treatment protocols, can affect the heart. Children who received this drug may need periodic cardiac evaluations
• Fertility: Most survivors have normal fertility, but some treatments can affect reproductive function. This is discussed as survivors reach appropriate age
• Second cancers: There is a slightly increased risk of developing another cancer later in life, particularly if radiation was given. This risk is monitored through regular health screenings
• Growth and development: Most children develop normally, but those who received abdominal radiation may have some asymmetric growth affecting the spine or soft tissues

Emotional and Social Recovery

The psychological impact of cancer treatment affects the entire family. Children may need time to process their experience and return to normal activities. Parents often experience ongoing anxiety about their child's health. Resources that can help include:

• Psychological support services at the treating center
• Parent support groups and survivor networks
• School reintegration programs
• Family counseling if needed

Vaccinations After Treatment

Chemotherapy and sometimes radiation therapy can affect the immune system and may reduce the effectiveness of previous vaccinations. After treatment is complete and the immune system has recovered (typically 3-6 months), children often need to receive certain vaccinations again according to an individualized schedule developed by their healthcare team. Live vaccines must be delayed until the immune system has fully recovered.

When and Where Should You Seek Medical Care?

Seek prompt medical attention if you notice any unexplained abdominal swelling or mass in your child, blood in the urine, persistent fever without obvious cause, or significant changes in appetite or energy level. Your child's pediatrician can perform initial evaluation and refer to specialists if needed.

Recognizing when to seek medical care is important for any parent. While Wilms tumor is rare, prompt evaluation of concerning symptoms leads to earlier diagnosis and treatment. The symptoms of Wilms tumor can overlap with many other, more common conditions, so medical evaluation is needed to determine the cause.

Symptoms That Require Evaluation

Contact your child's doctor if you notice:

• A lump, mass, or swelling in the abdomen
• One side of the abdomen appearing larger than the other
• Blood in the urine (pink, red, or dark brown)
• Persistent or recurrent fever without obvious infection
• Unexplained weight loss or poor appetite
• Abdominal pain that doesn't go away
• High blood pressure (often detected during routine check-ups)

While these symptoms have many possible causes, they warrant evaluation by a healthcare provider. If an abdominal mass is found, referral to a pediatric center with expertise in childhood cancers ensures access to specialists who can provide optimal evaluation and treatment.

Specialized Pediatric Cancer Centers

Children with suspected or confirmed Wilms tumor should be evaluated and treated at a specialized pediatric cancer center. These centers have multidisciplinary teams including pediatric oncologists, surgeons, radiologists, pathologists, and support staff experienced in treating children with cancer. They also participate in clinical research that continues to improve treatment outcomes.