Overview
Definition:
Post-streptococcal glomerulonephritis (PSGN) is an acute nephritic syndrome that develops after an infection with nephritogenic strains of group A beta-hemolytic streptococci (GABHS)
It is characterized by hematuria, edema, hypertension, and renal insufficiency
It is the most common glomerulonephritis in children worldwide.
Epidemiology:
PSGN is more common in children aged 6-7 years but can occur at any age
It is more prevalent in developing countries and is often associated with poor hygiene and crowded living conditions
Outbreaks can occur in schools and communities
Males are more frequently affected than females
Latent period varies from 1-2 weeks after pharyngeal infection and 2-3 weeks after cutaneous infection.
Clinical Significance:
Understanding PSGN is crucial for pediatricians and residents as it is a common cause of acute kidney injury in children
Early diagnosis and appropriate management are essential to prevent long-term complications such as chronic kidney disease and hypertension
Familiarity with serological markers like ASO titers and complement levels aids in establishing the diagnosis and differentiating it from other nephropathies.
Clinical Presentation
Symptoms:
Hematuria, often described as cola-colored or smoky urine
Edema, typically periorbital and lower extremity
Hypertension
Malaise and fatigue
Decreased urine output (oliguria)
Abdominal pain
Fever may be present early in the illness
Cough and dyspnea if pulmonary edema develops.
Signs:
Edema, particularly periorbital in the morning and pitting edema in the lower extremities
Elevated blood pressure
Mild fever
Tenderness in the costovertebral angle
Signs of fluid overload such as rales, jugular venous distension, and ascites (rare).
Diagnostic Criteria:
The diagnosis is typically made in a child with the acute onset of hematuria, edema, and hypertension following a recent streptococcal infection
Supporting evidence includes elevated antistreptolysin O (ASO) titer or other streptococcal antibody titers (e.g., anti-DNase B), and low serum complement levels (C3)
Renal biopsy is usually not required for diagnosis in typical cases but may be considered in atypical presentations or severe disease.
Diagnostic Approach
History Taking:
Inquire about a recent sore throat, skin infection (impetigo), or other symptoms suggestive of GABHS infection
Ask about the onset and duration of hematuria, edema, and hypertension
Assess for signs of fluid overload and any history of kidney disease
Note any recent antibiotic use.
Physical Examination:
Perform a thorough physical examination focusing on vital signs (blood pressure, heart rate, respiratory rate), presence and extent of edema (periorbital, sacral, extremities), assessment for signs of fluid overload (rales, distended neck veins, ascites), and abdominal tenderness.
Investigations:
Urinalysis: Hematuria (microscopic or macroscopic), red blood cell casts, proteinuria (usually <1 g/day)
Serum creatinine and BUN: To assess renal function and severity of azotemia
Complete blood count (CBC): May show mild anemia due to hemodilution or inflammation
Serological tests: Antistreptolysin O (ASO) titer (elevated in most patients after pharyngeal infection, may be normal after skin infection)
Anti-DNase B titer (useful after skin infection)
Complement levels: Low C3 is characteristic
C4 and CH50 may also be low
Usually normalizes within 6-8 weeks.
Differential Diagnosis:
Other causes of acute glomerulonephritis: IgA nephropathy
Henoch-Schönlein purpura nephritis
Lupus nephritis
Vasculitis
Hemolytic uremic syndrome (HUS)
Minimal change disease (presents with nephrotic range proteinuria and edema without hypertension or significant hematuria)
Membranoproliferative glomerulonephritis.
Management
Initial Management:
Primarily supportive care aimed at managing hypertension and fluid overload
Strict fluid and salt restriction
Bed rest is usually recommended during the acute phase
Hospitalization may be required for severe hypertension, significant edema, or acute kidney injury.
Medical Management:
Hypertension management: Diuretics (furosemide) for edema and hypertension
Antihypertensive medications such as calcium channel blockers (nifedipine), ACE inhibitors (enalapril), or hydralazine if needed
Antibiotics: Not indicated for treatment of PSGN itself but should be administered to eradicate any remaining streptococcal infection, especially if pharyngitis is still present
Penicillin is the drug of choice.
Surgical Management:
Not applicable for the management of PSGN
Focus is on medical management and supportive care.
Supportive Care:
Monitoring of blood pressure, fluid balance (intake/output), and daily weights
Close monitoring of renal function (serum creatinine, BUN)
Education for the family regarding the condition, prognosis, and follow-up recommendations
Dietary modifications (low salt, fluid restriction) are critical.
Complications
Early Complications:
Hypertensive encephalopathy
Acute pulmonary edema
Acute heart failure
Rapidly progressive glomerulonephritis (rare)
Acute kidney injury requiring dialysis (rare, usually in severe cases).
Late Complications:
Most children recover fully
However, a small percentage may develop chronic kidney disease, persistent hypertension, or recurrent hematuria
Rarely, progression to end-stage renal disease can occur.
Prevention Strategies:
Prompt diagnosis and treatment of streptococcal pharyngitis and skin infections can reduce the incidence of PSGN
Public health measures to improve hygiene and living conditions are also important.
Prognosis
Factors Affecting Prognosis:
Age (younger children tend to have a better prognosis)
Severity of initial presentation
Presence of significant renal insufficiency
Persistence of renal abnormalities on follow-up
Adherence to medical advice and management.
Outcomes:
The vast majority of children with PSGN recover completely with normal renal function
Resolution of hematuria and proteinuria typically occurs within weeks to months
Hypertension and edema usually resolve promptly
Recurrence is rare.
Follow Up:
Regular follow-up is essential for at least 1-2 years
This includes monitoring of blood pressure, urinalysis for hematuria and proteinuria, and renal function tests (serum creatinine)
Long-term follow-up may be necessary for children with persistent abnormalities.
Key Points
Exam Focus:
Key diagnostic triad: hematuria, edema, hypertension post-streptococcal infection
Elevated ASO titer and low C3 complement are classic findings
Differentiate from IgA nephropathy (ASO normal, C3 normal)
Prognosis is generally excellent in children.
Clinical Pearls:
Remember that ASO titers can be normal after a cutaneous streptococcal infection, in which case anti-DNase B is a more reliable marker
Cola-colored urine is a classic sign of hematuria in PSGN
Early management of hypertension and fluid overload is paramount.
Common Mistakes:
Failing to consider PSGN in a child with acute nephritic syndrome and a history of recent infection
Misinterpreting normal ASO titers after skin infections
Delaying diagnosis and management of hypertension
Not performing a complete urinalysis and renal function tests
Overlooking the importance of complement levels in diagnosis.