What is the management approach for a pediatric patient with Post-Infectious Glomerulonephritis (PIGN)?

Management of Post-Infectious Glomerulonephritis (PIGN) in Pediatric Patients

The management of PIGN in children is primarily supportive, focusing on sodium restriction, diuretics for fluid overload, and antihypertensives for blood pressure control, with antibiotics administered to reduce antigenic load even when active infection has resolved. 1, 2

Antibiotic Therapy

Administer penicillin (or erythromycin if penicillin-allergic) regardless of whether active infection is still present to decrease the antigenic load and eliminate nephritogenic strains of Streptococcus pyogenes from the community. 1, 3, 2 This is a critical point that clinicians often miss—the goal is not to treat active infection but to reduce the streptococcal antigen burden that drives the immune complex formation. 2

• Cephalosporins (such as co-amoxiclav or first-generation cephalosporins like cephalexin) are appropriate alternatives for non-anaphylactic penicillin allergies or when beta-lactamase producing organisms are suspected. 2
• During outbreaks, systemic antimicrobials should be used to eliminate nephritogenic strains from the community. 3, 2

Supportive Management of Nephritic Syndrome

Fluid and Sodium Management

Restrict dietary sodium to <2.0 g/day (<90 mmol/day) as the first-line intervention for managing both edema and hypertension. 4, 1, 2 This is more important than immediately reaching for medications. 2

• Monitor fluid status closely and adjust diuretic therapy based on clinical response. 2
• Use loop diuretics as first-line agents for managing fluid overload and hypertension. 2
• Watch for diuretic-related adverse effects including hyponatremia, hypokalemia, GFR reduction, and volume depletion. 2

Blood Pressure Control

Target blood pressure at ≤50th percentile for age, sex, and height using ambulatory blood pressure monitoring in children. 2

• Diuretics serve dual purposes: managing fluid overload and controlling blood pressure. 2
• Add antihypertensive medications if blood pressure remains elevated despite sodium restriction and diuretics. 1, 2

Dietary Modifications

• If nephrotic-range proteinuria is present, restrict dietary protein to 0.8-1 g/kg/day. 4
• Provide high-energy diet to maintain nutritional status while keeping salt content low. 1

Metabolic Management

Treat metabolic acidosis if serum bicarbonate is <22 mmol/L. 2

Renal Replacement Therapy

Provide dialysis only for severe acute kidney injury with specific indications: 2

• Uremia with clinical symptoms
• Refractory fluid overload despite maximal medical therapy
• Life-threatening hyperkalemia

Immunosuppressive Therapy

Avoid immunosuppression in typical PIGN cases, as the disease is self-limited with excellent prognosis. 2, 5, 6

• Reserve corticosteroids ONLY for severe crescentic PIGN with rapidly progressive glomerulonephritis, and understand that this recommendation is based on anecdotal evidence only. 2, 7, 8
• The vast majority of children recover completely without immunosuppression. 5, 6

Monitoring Protocol

Short-term Monitoring (Weekly to Monthly)

• Serum creatinine and eGFR to assess kidney function 1, 3
• Blood pressure control 1, 3
• Urinalysis for hematuria and proteinuria (measure albumin-to-creatinine or protein-to-creatinine ratio) 1, 3, 2
• Electrolytes and acid-base status 1, 3

Long-term Monitoring (8-12 Weeks and Beyond)

C3 complement levels should normalize by 8-12 weeks in uncomplicated PIGN. 1, 3, 2

• If C3 remains low beyond 12 weeks, perform kidney biopsy to exclude C3 glomerulonephritis (C3GN). 3, 2
• Continue monitoring for persistent proteinuria, hypertension, and progression to chronic kidney disease, as some patients require long-term follow-up. 7

Indications for Kidney Biopsy

Perform kidney biopsy when: 3, 2

• Diagnosis is uncertain or presentation is atypical
• C3 complement remains persistently low beyond 12 weeks
• Rapidly progressive glomerulonephritis with crescentic changes is suspected
• Alternative diagnoses need to be excluded (IgA-dominant infection-related GN, lupus nephritis, ANCA vasculitis, anti-GBM disease)

Diagnostic Workup to Exclude Alternative Diagnoses

When evaluating a child with suspected PIGN, exclude other causes of acute glomerulonephritis: 2

• Lupus nephritis: Check ANA and anti-dsDNA (lupus causes low C3 AND low C4, unlike PIGN)
• ANCA vasculitis: Check PR3-ANCA and MPO-ANCA
• Anti-GBM disease: Check anti-GBM antibodies
• Cryoglobulinemia: Check cryoglobulins and rheumatoid factor

If ASO titers are normal but clinical suspicion remains high, measure alternative streptococcal antibodies (anti-DNAse B and anti-hyaluronidase). 2

Common Pitfalls to Avoid

• Do not withhold antibiotics even when active infection is no longer evident—the goal is antigenic load reduction, not treating active infection. 2
• Do not routinely use immunosuppression—most cases resolve spontaneously and the evidence for immunosuppression is anecdotal at best. 2
• Do not delay kidney biopsy if C3 fails to normalize by 8-12 weeks, as this may indicate C3GN rather than PIGN. 3, 2
• Do not assume all cases are streptococcal—consider IgA-dominant infection-related GN, particularly in older patients with staphylococcal infections. 2

Prognosis

PIGN resolves completely and spontaneously in most children, with excellent long-term outcomes, preserved renal function, and no recurrence. 5, 6, 7 However, a small subset may develop persistent proteinuria, hypertension, or progression to chronic kidney disease, necessitating long-term monitoring. 7