What are the potential complications of post-infectious glomerulonephritis (PIGN) in pediatric and young adult patients?

Complications of Post-Infectious Glomerulonephritis (PIGN)

PIGN can cause significant acute complications requiring intensive care, including acute kidney injury (20-46% requiring dialysis), hypertensive emergency (19%), cardiac failure (11%), and encephalopathy (4%), with long-term outcomes varying dramatically by age—children typically achieve complete recovery while adults face a 33% risk of progression to end-stage renal disease. 1, 2

Acute Complications

Cardiovascular and Neurological Emergencies

• Hypertensive emergency occurs in approximately 19% of pediatric cases and requires immediate blood pressure control with diuretics and antihypertensive medications 1
• Cardiac failure develops in 11% of cases due to fluid overload and hypertension, necessitating aggressive diuretic therapy and sodium restriction to <2.0 g/day 1, 3
• Hypertensive encephalopathy presents in 4% of cases with seizures and altered mental status, requiring urgent blood pressure reduction 1
• Retinopathy can occur as a hypertensive complication in rare cases (1.4%) 1

Renal Complications

• Acute kidney injury (AKI) develops in 20-46% of patients, with severity ranging from mild elevation in creatinine to dialysis-requiring renal failure 1, 2
  • In pediatric series, 20% of AKI cases reach AKIN stage 3, and approximately 7% require hemodialysis 1
  • In elderly patients (≥65 years), 46% require acute dialysis at presentation 2
• Rapidly progressive glomerulonephritis (RPGN) with crescentic features can occur, particularly in adults and immunocompromised patients 4, 2
  • Crescents in >30% of glomeruli predict poor renal outcome 5
  • This severe form may warrant consideration of high-dose glucocorticoids, though evidence is anecdotal 3

Metabolic Complications

• Fluid overload with pulmonary edema occurs in approximately 6% of cases, requiring diuretic therapy and potentially dialysis 1
• Hyperkalemia can be life-threatening in severe AKI and may necessitate emergency dialysis 3
• Metabolic acidosis develops when serum bicarbonate falls below 22 mmol/L and requires treatment 3

Chronic Complications and Long-Term Outcomes

Age-Dependent Prognosis

• Children have excellent prognosis with complete recovery expected in the vast majority of cases, particularly with epidemic/classic post-streptococcal disease where >80% return to premorbid kidney function 6, 4
• Adults (≥65 years) face dramatically worse outcomes: only 22% achieve complete recovery, 44% have persistent renal dysfunction, and 33% progress to end-stage renal disease 2

Persistent Renal Abnormalities

• Residual renal injury at discharge occurs in approximately 32% of pediatric cases 1
• Persistent proteinuria and hematuria at 12 months occurs in 10% of adult patients and independently predicts poor renal outcome 5
• Chronic kidney disease develops in 11% of adults with serum creatinine >1.5 mg/dL at one year 5
• Persistent hypertension occurs in 2% of cases at 12 months 5

Complement Abnormalities

• Persistently low C3 beyond 12 weeks indicates possible alternative diagnosis such as C3 glomerulonephritis (C3GN) rather than true PIGN and mandates kidney biopsy 3, 6
• Normal C3 recovery timeline is 8-12 weeks; failure to normalize requires investigation for complement-mediated glomerular disease 3

Risk Factors for Poor Outcomes

Patient Characteristics

• Age >40 years significantly increases risk of progression to ESRD 5
• Male gender predicts worse renal outcome 5
• Immunocompromised state (present in 61% of elderly patients) including diabetes or malignancy increases complication risk 2
• Diabetes mellitus independently predicts progression to ESRD 2

Clinical and Laboratory Predictors

• Serum creatinine >2 mg/dL at one week is an independent risk factor for poor renal outcome at one year 5
• Dialysis requirement at presentation predicts ESRD 2
• Higher creatinine at biopsy correlates with worse long-term outcomes 2

Histological Predictors

• Crescents in >30% of glomeruli predict poor renal outcome 5
• Diabetic glomerulosclerosis on biopsy predicts ESRD in diabetic patients 2
• Greater tubular atrophy and interstitial fibrosis predict progression to ESRD 2

Special Considerations and Pitfalls

Atypical Presentations Requiring Biopsy

• Kidney biopsy is indicated when diagnosis is uncertain, atypical presentation occurs, C3 remains persistently low beyond 12 weeks, or rapidly progressive glomerulonephritis develops 3, 4
• IgA-dominant PIGN represents a distinct subtype occurring in 17% of elderly patients, particularly with staphylococcal infections, and requires biopsy for diagnosis 2, 3

Causative Organism Considerations

• In elderly patients, staphylococcus (46%) has replaced streptococcus (16%) as the most common causative agent, with skin infections being the most common site 2
• Non-streptococcal organisms are emerging as main etiological agents in high-income countries 4
• Pneumococcal pneumonia can rarely cause PIGN in adults and may respond to steroid therapy in severe crescentic cases 7

Monitoring Requirements

• Short-term monitoring must include kidney function, blood pressure control, urinalysis for hematuria and proteinuria, electrolytes, and acid-base status 8
• Long-term follow-up requires C3 complement levels at 8-12 weeks to confirm normalization, with persistent abnormalities mandating further investigation 6
• Regular assessment of kidney function, blood pressure, proteinuria, and hematuria is essential even in patients who appear to recover initially 6