Management of Suspected Wilms Tumor in an 18-Month-Old
In an 18-month-old with a suspected Wilms tumor presenting as a hard abdominal mass, proceed directly to imaging with ultrasound as the next step—do not perform biopsy. 1
Initial Diagnostic Approach
Ultrasound is the Optimal First Step
Abdominal ultrasound should be performed immediately to confirm the renal origin of the mass, evaluate for bilateral disease, and assess for inferior vena cava tumor extension using Doppler interrogation. 1
Ultrasound is the preferred initial imaging modality because it is widely available, lacks ionizing radiation, can be performed without sedation, and has high sensitivity for detecting renal masses. 2, 1
The bladder should also be examined during the ultrasound to assess for any additional lesions. 2
Why Biopsy is NOT Recommended
Biopsy should be avoided in suspected Wilms tumor because it risks tumor rupture and upstaging, which would necessitate more intensive chemotherapy and radiation therapy. 3
The diagnosis of Wilms tumor is typically made based on imaging characteristics combined with clinical presentation, not tissue diagnosis prior to treatment initiation. 3, 4
Definitive tissue diagnosis is obtained at the time of surgical resection (radical nephroureterectomy with lymph node sampling), not through pre-treatment biopsy. 3
Subsequent Management Algorithm
After Ultrasound Confirmation
If ultrasound confirms a renal mass consistent with Wilms tumor, proceed to contrast-enhanced CT of the chest, abdomen, and pelvis for complete staging evaluation. 3, 4
MRI may be considered as an alternative to CT, particularly for evaluating bilateral tumors, detecting nephrogenic rests, and pre-operative planning for potential nephron-sparing surgery. 2
Treatment Pathway
For large or potentially unresectable tumors (common in resource-limited settings), preoperative chemotherapy with vincristine and actinomycin for 4 weeks is recommended, followed by delayed surgery at week 5. 3
For metastatic disease, preoperative chemotherapy extends to 6 weeks with the addition of doxorubicin, with surgery at week 7. 3
Radical nephroureterectomy with lymph node sampling remains the cornerstone surgical procedure, though nephron-sparing surgery should be considered in bilateral cases or genetic predisposition syndromes. 2, 3
Critical Considerations
Genetic Predisposition Screening
Consider genetic testing for predisposition syndromes (WT1, TRIM28, REST, CTR9, DIS3L2, Beckwith-Wiedemann syndrome, DICER1) as part of comprehensive evaluation, particularly if bilateral disease, very young age, or syndromic features are present. 5
Patients with identified genetic predisposition syndromes require renal ultrasound surveillance every 3 months until age 7-8 years for family members and contralateral kidney monitoring. 2, 5
Common Pitfalls to Avoid
Never perform biopsy as the initial diagnostic step in suspected Wilms tumor—this is a critical error that can worsen prognosis through tumor spillage. 3
Do not reassure and observe an 18-month-old with a hard abdominal mass—this represents a medical emergency requiring immediate evaluation. 6
Do not proceed directly to MRI or CT without first performing ultrasound, as ultrasound provides adequate initial characterization while avoiding radiation exposure and sedation. 1