What is the best initial step in managing a 12-year-old boy with hematuria (red urine), following a recent fever and sore throat, and minor abdominal trauma?

Best Initial Step in Management

The best initial step is to perform a thorough urinalysis with microscopic examination to differentiate between post-streptococcal glomerulonephritis (given the recent pharyngitis) and traumatic hematuria, as this fundamentally determines whether the patient requires nephrology evaluation versus trauma imaging. 1, 2

Clinical Reasoning and Diagnostic Approach

This 12-year-old presents with two competing etiologies for hematuria that require immediate differentiation:

Key Historical Features to Assess

• Recent streptococcal infection (2 weeks ago): The timing is classic for post-streptococcal glomerulonephritis, which typically presents 1-3 weeks after pharyngitis 1, 2
• Minor abdominal trauma (yesterday): While trauma is present, it was minor and the patient has no pain or other symptoms 1
• Character of urine: Determine if the urine is tea-colored (suggesting glomerular origin) versus bright red (suggesting lower tract or traumatic origin) 1

Critical Urinalysis Components

Perform microscopic urinalysis specifically looking for:

• Proteinuria (>2+ by dipstick): Indicates glomerular disease 1, 2
• Red blood cell casts: Pathognomonic for glomerulonephritis 1, 2
• Dysmorphic red blood cells: Best seen with phase contrast microscopy, indicates glomerular source 1, 2
• White blood cells and organisms: Would indicate urinary tract infection 1

Decision Algorithm Based on Urinalysis Results

If urinalysis shows glomerular features (proteinuria, RBC casts, dysmorphic RBCs):

• Obtain blood urea nitrogen, serum creatinine, complete blood count with platelets 1, 2
• Check complement levels (C3, C4) and anti-streptolysin O titers to confirm post-streptococcal glomerulonephritis 1
• Measure blood pressure, as hypertension commonly accompanies acute glomerulonephritis 1
• No imaging is indicated initially for isolated glomerulonephritis 1, 2

If urinalysis shows isolated hematuria without glomerular features:

• The minor trauma becomes more relevant as a potential cause 1
• However, given the trauma was truly minor (no pain, no symptoms), and the mechanism was not significant, imaging is usually not appropriate 1
• The ACR Appropriateness Criteria state that imaging is usually not appropriate for isolated microscopic hematuria without concerning trauma features 1

When Imaging Would Be Indicated

CT abdomen/pelvis with IV contrast would be appropriate if the patient had: 1, 3

• Macroscopic (gross) hematuria following trauma 1
• Microscopic hematuria with concerning trauma features: deceleration injury, localized flank pain, flank ecchymosis, hemodynamic instability, or falling hemoglobin 1
• History suggesting significant mechanism of injury 1

The decision to perform CT should be based on history and mechanism of injury, not urinalysis alone. 1

Critical Pitfalls to Avoid

• Do not assume the trauma caused the hematuria without ruling out glomerulonephritis, especially given the classic 2-week post-pharyngitis timing 1, 2
• Do not order CT imaging for truly minor trauma with isolated microscopic hematuria and no concerning features, as this exposes the child to unnecessary radiation 1, 2
• Do not miss post-streptococcal glomerulonephritis by attributing all hematuria to trauma, as this can lead to delayed diagnosis of potentially serious renal disease 1
• Do not skip microscopic examination of urine, as dipstick alone cannot differentiate glomerular from non-glomerular causes 1, 2

Evidence Quality and Nuances

The ACR Appropriateness Criteria (2018) provide the strongest guideline evidence, clearly stating that imaging is not appropriate for isolated microscopic hematuria without proteinuria or concerning trauma features 1. The World Journal of Emergency Surgery guidelines (2019) emphasize that in children, significant renal injuries can occur without hematuria, but the decision for imaging must be based on mechanism and clinical findings, not hematuria alone 1. The convergence of these guidelines supports a urinalysis-first approach to determine the appropriate pathway.