What is the best initial imaging study for a 5-year-old patient, status post motor vehicle accident (MVA), presenting with hematuria and normal bowel sounds (NBS), to evaluate for potential renal injury: abdominal computed tomography (Abd CT) or renal ultrasound (Renal U/S)?

From the Guidelines

For a 5-year-old child with hematuria following a motor vehicle accident (MVA), the best initial imaging study would be an Abdominal CT scan (option A). While renal ultrasound is less invasive and avoids radiation exposure, CT is preferred in trauma settings because it can comprehensively evaluate for renal lacerations, perirenal hematomas, vascular injuries, and other abdominal organ injuries that commonly occur in MVAs. According to the American College of Radiology Appropriateness Criteria 1, CT of the abdomen and pelvis with IV contrast is usually appropriate in the child presenting with macroscopic hematuria in the setting of trauma. This recommendation is further supported by the World Journal of Emergency Surgery 1, which states that CT scan with intravenous contrast is considered the gold standard in blunt and penetrating trauma. The child's presentation with hematuria after trauma raises significant concern for renal injury, and missing associated injuries could lead to serious complications. Although radiation exposure is a consideration in pediatric patients, the benefit of accurate diagnosis in trauma outweighs this risk. The findings from the CT would guide whether conservative management is appropriate or if surgical intervention is necessary, making it the preferred choice for USMLE Step 2 purposes.

Some key points to consider in this scenario include:

• The presence of hematuria in a child after trauma necessitates a thorough evaluation to rule out significant renal or urinary tract injury.
• CT scans provide superior anatomical detail and can detect urinary extravasation, which is crucial in determining management.
• The American College of Radiology Appropriateness Criteria 1 and the World Journal of Emergency Surgery 1 both recommend CT scans as the initial imaging study in children with hematuria after trauma.
• While radiation exposure is a concern in pediatric patients, the benefit of accurate diagnosis in trauma outweighs this risk.

In terms of specific recommendations, the following can be made:

• Abdominal CT scan with IV contrast is the preferred initial imaging study in children with hematuria after trauma.
• Renal ultrasound may be considered as an alternative in certain situations, such as in patients with minor trauma or in whom CT is contraindicated.
• The decision to perform a CT scan should be based on the individual patient's clinical presentation and the suspected severity of the injury.

From the Research

Imaging Modalities for Hematuria in Children

• For a 5-year-old patient who presents with hematuria after a motor vehicle accident, the best imaging modality is a topic of discussion in the provided studies.
• According to 2, radiological evaluation consisting of abdominal and pelvic computerized tomography (CT) should be performed only in patients with 50 or greater red blood cells on urinalysis, hypotension at presentation, or based on the severity of the mechanism of injury.
• However, 3 suggests that CT is the preferred modality for imaging the urinary tract in patients with significant blunt abdominal trauma, penetrating trauma, and hematuria.

Comparison of Imaging Modalities

• Ultrasound (Renal U/S) may not be sufficient for imaging of hematuria, as stated in 4, and it is often difficult to differentiate renal transitional cell carcinoma from other causes of filling defects of the renal collecting system using ultrasound alone.
• CT urography, which includes an unenhanced scan, the nephrographic phase, and the excretory phase, is useful for evaluating gross hematuria, as mentioned in 5.
• In the context of a child with hematuria after a motor vehicle accident, an abdominal CT (Abd CT) might be more appropriate than a renal ultrasound (Renal U/S) due to its ability to provide more detailed information about the urinary tract and surrounding organs.

Recommendations for Imaging in Children with Hematuria

• Based on the studies provided, the best answer for USMLE Step 2 purposes would be to recommend an abdominal CT (Abd CT) for a 5-year-old patient who presents with hematuria after a motor vehicle accident, especially if the patient has 50 or greater red blood cells on urinalysis, hypotension, or a severe mechanism of injury, as suggested by 2 and 3.