What is the most appropriate next step in the diagnostic work-up for a child with a palpable abdominal mass and hematuria?

Diagnostic Workup for Child with Palpable Abdominal Mass and Hematuria

The most appropriate next step is plain abdominal radiography and abdominal ultrasonography (Option D), with ultrasound being the critical component for evaluating this child's palpable renal mass and hematuria.

Primary Recommendation

Abdominal ultrasound must be performed immediately as the first-line imaging modality for this child presenting with a palpable flank mass and hematuria. 1, 2 The American College of Radiology explicitly recommends ultrasound as the initial imaging for evaluating abdominal masses in children with hematuria, as it effectively displays kidney anatomy, size, and position while screening for structural lesions. 1

Clinical Context and Differential Diagnosis

This presentation—a well-appearing child with a palpable right flank mass, hypertension (130/80 mmHg), and significant hematuria (40 erythrocytes per high-power field with +3 hemoglobin)—raises immediate concern for:

• Wilms tumor (nephroblastoma): Most likely given the age, palpable flank mass, and hematuria 1, 2
• Other renal masses: Neuroblastoma, renal cell carcinoma, or mesoblastic nephroma 3
• Hydronephrosis with obstruction: Less likely given the firm mass character 3

The hypertension further supports a renal parenchymal process requiring urgent evaluation. 3

Why Ultrasound is Essential First

Ultrasound serves multiple critical diagnostic functions that must be completed before any other imaging: 1, 2

• Confirms the renal origin of the mass and differentiates it from other abdominal pathology 2
• Assesses the contralateral kidney for bilateral involvement, which occurs in 5-10% of Wilms tumor cases 1
• Evaluates for inferior vena cava involvement and renal vein extension, critical for surgical planning 1, 2
• Determines tumor size and extent within the kidney 2
• Requires no ionizing radiation, making it ideal for pediatric patients 1
• Can be performed without anesthesia or contrast, allowing immediate evaluation 1

Role of Plain Radiography

Plain abdominal radiography (KUB) has a complementary but limited role in this scenario:

• May detect calcifications that could suggest neuroblastoma (which calcifies in 50-80% of cases) versus Wilms tumor (which rarely calcifies) 3
• Can identify radiopaque stones if nephrolithiasis is contributing to hematuria, though this is less likely given the palpable mass 3
• Provides baseline anatomic information about bowel gas patterns and organ displacement 4

However, radiography alone is insufficient because it has poor contrast resolution and cannot adequately characterize soft tissue masses. 4

Why CT is NOT the Initial Test

The American College of Radiology explicitly advises against proceeding directly to CT without ultrasound confirmation of renal origin. 2 CT is generally not indicated as a first-line test for isolated macroscopic hematuria in children. 3

CT has a secondary role only after ultrasound confirms a renal mass: 3

• Contrast-enhanced CT helps define local extent of disease and vascular invasion (particularly for Wilms tumor) 3
• CT is used to detect metastases after the mass is characterized 3

Why MRI is NOT the Initial Test

MRI is not indicated as the first-line test for isolated macroscopic hematuria. 3 While MRI may provide value for further diagnosis of suspected renal masses or nutcracker syndrome, it should only be considered after initial ultrasound evaluation. 3

Critical Pitfalls to Avoid

Do not delay imaging by assuming this represents isolated hematuria requiring no immediate workup. 1 The presence of a palpable abdominal mass fundamentally changes the clinical scenario from isolated hematuria to suspected renal neoplasm, requiring urgent evaluation. 3

Do not skip ultrasound and proceed directly to CT. 2 Ultrasound may reveal the mass is not renal in origin, completely changing the diagnostic approach. 2 Additionally, unnecessary radiation exposure in children should be avoided when ultrasound can provide the necessary diagnostic information. 1

Do not forget to examine the bladder during ultrasound. 3 The bladder should be distended with urine and examined for polyps, masses, or vascular lesions that could contribute to hematuria. 3

Sequential Diagnostic Algorithm

1. Immediate ultrasound of kidneys and bladder to characterize the mass, assess bilateral involvement, and evaluate vascular extension 1, 2

2. Plain radiography (KUB) can be performed concurrently to assess for calcifications and provide complementary anatomic information 3

3. If ultrasound confirms a renal mass: Proceed urgently to chest CT for staging to evaluate for pulmonary metastases, as this significantly impacts treatment intensity 1, 2

4. If ultrasound confirms a renal mass: Consider contrast-enhanced abdominal CT or MRI to define local extent, vascular invasion, and lymph node involvement 3

Additional Urgent Workup

Beyond imaging, this child requires: 3

• Blood urea nitrogen and serum creatinine to assess renal function 3
• Complete blood count with platelets 3
• Blood pressure monitoring given the documented hypertension 3