What is the next best investigation for a child with Henoch-Schönlein Purpura (HSP)?

Next Best Investigation for a Child with Henoch-Schönlein Purpura (HSP)

Urinalysis with microscopic examination is the most important initial investigation for a child with HSP to assess for renal involvement, which is the primary determinant of long-term prognosis.

Initial Evaluation for Renal Involvement

Urinalysis Assessment

• Urinalysis with microscopy should be performed immediately to detect:
  • Hematuria (microscopic or macroscopic)
  • Proteinuria (quantitative measurement)
  • Red blood cell casts
  • Deformed red blood cells (using phase contrast microscopy) 1

Additional Basic Laboratory Tests

• Complete blood count with platelets
• Blood urea nitrogen (BUN)
• Serum creatinine
• Spot urine protein-to-creatinine ratio (for quantification of proteinuria)

Monitoring Protocol

• Urinalysis should be performed:
  • Weekly for the first month after diagnosis
  • Every 2 weeks for the second month
  • Monthly for the next 4-6 months
  • Then every 3 months until 1 year after diagnosis 1, 2

Indications for Renal Biopsy

Renal biopsy should be performed in children with HSP who present with:

• Decreased renal function at presentation
• Severe nephrotic syndrome or nephritic syndrome
• Persistent heavy proteinuria (>1 g/day/1.73 m²) despite optimal therapy with ACE inhibitors/ARBs for 3-6 months 1, 2

Risk Stratification Based on Initial Findings

Low Risk

• Normal urinalysis or minimal abnormalities
• Continue monitoring with serial urinalysis

Moderate Risk

• Persistent proteinuria (0.5-1 g/day/1.73 m²)
• Consider ACE inhibitor or ARB therapy 1, 2

High Risk

• Nephrotic-range proteinuria
• Elevated creatinine
• Hypertension
• Consider renal biopsy and more aggressive therapy 1

Important Clinical Considerations

• Renal involvement occurs in approximately 20-60% of children with HSP 3, 4
• Most children develop renal manifestations within 2 weeks of disease onset, while adults may develop hematuria up to 5 weeks after onset 5
• Factors associated with higher risk of nephritis include:
  • Older age at onset
  • GI bleeding
  • Central nervous system involvement 6
  • Persistent purpura for >1 month 5

Common Pitfalls to Avoid

1. Inadequate follow-up duration: Renal manifestations may appear weeks after the initial presentation of HSP, so monitoring should continue for at least 6 months
2. Missing nephrotic syndrome: Patients with abdominal pain at disease onset have a significantly higher probability of developing nephrotic syndrome 5
3. Premature discontinuation of monitoring: Even children with initially normal urinalysis should have continued monitoring as late-onset nephritis can occur
4. Failure to recognize crescentic nephritis: This severe form requires aggressive immunosuppressive therapy and has poorer outcomes 1

Remember that renal involvement is the most important prognostic factor in determining morbidity and mortality in HSP. Early detection through appropriate urinalysis monitoring is essential for timely intervention and improved outcomes.