Post-Streptococcal Glomerulonephritis (PSGN) Clinical Overview
I. The "On-Call" Snapshot
Clinical Significance in Malaysia: This is the most common cause of acute nephritis in children locally. You need to recognise it to manage acute kidney injury (AKI), severe hypertension, and fluid overload.
High-Yield Definition: "An acute nephritic syndrome... characterised by the abrupt onset of haematuria (microscopic or macroscopic), proteinuria, oedema, and hypertension, with or without renal insufficiency" following an infection with a nephritogenic strain of Group A beta-hemolytic Streptococcus (GAS). (Source: Malaysian Paediatric Protocols, 4th Ed.)
Clinical One-Liner: "Kid comes in puffy (edema), peeing 'teh tarik' (gross haematuria), with high BP, about 2 weeks after a sore throat or 4 weeks after a skin infection ('kudis')."
II. Etiology & Risk Factors
Etiology: An immune-mediated glomerulonephritis. It is not a direct infection of the kidney, but a delayed complication caused by glomerular deposition of immune complexes formed against nephritogenic strains of Streptococcus pyogenes (GAS).
Risk Factors:
Antecedent GAS Infection:
Pharyngitis: 1-2 weeks prior.
Pyoderma (Impetigo/Scabies): 3-6 weeks prior.
Age: Peak incidence 5-12 years. Rare under 3 years.
Sex: Male > Female (approx. 2:1).
Environment: Crowded living conditions, poor hygiene (risk factor for pyoderma).
III. Quick Pathophysiology
Infection: Patient gets infected with a nephritogenic GAS strain (e.g., pharyngitis, impetigo).
Immune Response: The body forms antibodies against streptococcal antigens (like SpeB, NAPlr).
Deposition: These circulating antigen-antibody immune complexes, or antigens that plant themselves in the glomerulus first, deposit in the glomerular basement membrane (GBM).
Inflammation: This deposition activates the complement system (classically, C3 is consumed, C4 is normal). This inflammatory cascade (glomerulonephritis) damages the glomeruli.
Clinical Effect:
Glomerular Damage: Increased GBM permeability -> Red blood cells and protein leak into urine (haematuria, proteinuria).
Reduced GFR: Inflammation reduces glomerular filtration -> Sodium and water retention -> Edema, hypertension, and oliguria.
IV. Classification
PSGN is not formally staged. It is classified by clinical presentation:
Subclinical/Asymptomatic: Most common. Discovered incidentally via urine screening (microscopic haematuria).
Acute Nephritic Syndrome: The classic presentation with edema, gross haematuria, and hypertension.
Rapidly Progressive Glomerulonephritis (RPGN): Rare (<1%). Presents with acute, severe renal failure. Biopsy shows crescents.
V. Clinical Assessment
🚩 Red Flags & Immediate Actions:
Severe Hypertension / Hypertensive Emergency (BP >99th centile + symptoms):
Symptoms: Severe headache, visual changes, vomiting, confusion, seizures.
Action: STAT IV antihypertensives (e.g., IV Labetalol, IV Hydralazine) as per paediatric protocol. Escalate to senior.
Reason: Risk of Posterior Reversible Encephalopathy Syndrome (PRES) or intracranial haemorrhage.
Oliguria / Anuria (<0.5 ml/kg/hr):
Action: Strict I/O chart, check RP and electrolytes (for K+), consider fluid challenge vs. restriction, escalate for urgent renal assessment.
Reason: Impending severe AKI.
Pulmonary Edema (Respiratory distress, tachypnoea, hypoxia, basal crepitations):
Action: Sit patient upright, high-flow O2, STAT IV Furosemide (1-2 mg/kg).
Reason: Severe fluid overload leading to heart failure.
Altered Mental Status / Seizures:
Action: Secure ABCs, check capillary blood glucose, check BP immediately (for encephalopathy), check electrolytes (for hyponatremia).
Reason: Likely hypertensive encephalopathy or severe electrolyte imbalance.
History:
Key Diagnostic Clues (The Classic Triad):
Edema: Starts periorbital (puffy eyes in the morning), later becomes peripheral (pedal edema) and generalised (ascites).
Gross Haematuria: "Tea-coloured," "cola-coloured," or "teh tarik."
Hypertension: May be asymptomatic or present with headache.
Symptom Breakdown:
Common (>50%): Edema (90%), gross haematuria (30-50%, but microscopic is near-universal), hypertension (50-90%), lethargy, oliguria.
Less Common (10-50%): Anorexia, vomiting, flank or abdominal pain.
Rare (<10%): Seizures, breathlessness (pulmonary edema).
Pertinent Negatives:
No purpuric rash on lower limbs (makes HSP less likely).
No recent bloody diarrhoea (makes HUS less likely).
No joint pain/swelling (makes HSP or SLE less likely).
No concurrent URTI (haematuria with pharyngitis suggests IgA nephropathy).
Physical Examination (OSCE Approach):
General Inspection: Patient may be lethargic. Look for "puffy face" (periorbital edema). Pitting edema over shins/sacrum. Signs of respiratory distress (tachypnoea, use of accessory muscles).
Vitals: Hypertension (check BP against age/height centile charts). Tachycardia (volume overload). Tachypnoea (pulmonary edema).
Disease-Specific Examination (System-based):
Cardiovascular:
Look: Raised JVP (hard to assess in young children).
Feel: Displaced apex beat (volume overload).
Auscultate: Gallop rhythm (S3), pulmonary crepitations at lung bases.
Abdomen:
Look: Abdominal distension (ascites).
Feel: May have shifting dullness. Kidneys are not usually ballotable.
Skin:
Look: Carefully inspect skin (especially limbs, scalp, behind ears) for healing impetigo lesions, crusts, or scratch marks from scabies.
Neurological:
Assess GCS, look for focal deficits (if hypertensive emergency).
Pertinent Negatives: No palpable purpura, no arthritis.
Differentiating Disease Stage:
Early / Mild Disease: Microscopic haematuria only, or mild periorbital edema, normotensive.
Intermediate / Moderate Disease: Gross haematuria, significant pitting edema, moderate hypertension controlled with orals.
Late / Severe Disease: Oliguric AKI, hypertensive emergency, signs of pulmonary edema.
Clinical Pearl: "Always ask about sore throat and skin infections ('kudis') in any child with edema or 'teh tarik' urine. The latent period is key: 1-2 weeks for pharyngitis, 3-6 weeks for pyoderma."
VI. Diagnostic Workflow
Differential Diagnosis:
IgA Nephropathy (Berger's Disease):
Points For: Gross haematuria, often after URTI.
Points Against: Classically syn-pharyngitic (haematuria occurs with or 1-3 days after URTI, not weeks later). Tends to be recurrent. C3 is normal.
How to Differentiate: Timing of haematuria relative to URTI. Serum C3 level (normal in IgA).
Henoch-Schönlein Purpura (HSP) Nephritis:
Points For: Nephritis (haematuria, proteinuria), can follow URTI.
Points Against: Lacks the classic HSP tetrad (palpable purpura, arthritis, abdominal pain).
How to Differentiate: Presence of the characteristic purpuric rash is key.
Membranoproliferative Glomerulonephritis (MPGN):
Points For: Presents as nephritic syndrome, C3 can be low.
Points Against: PSGN is much more common. In MPGN, the low C3 persists for >8 weeks.
How to Differentiate: Serial C3 levels. If C3 does not normalise by 6-8 weeks, suspect MPGN and refer to nephrology.
Investigations Plan:
Bedside / Initial (First 15 Mins):
Urine Dipstick (UFEME): Haematuria (3+ to 4+), Proteinuria (1+ to 2+). Look for red cell casts on microscopy (pathognomonic for glomerulonephritis).
BP Monitoring: Use correct cuff size. Check 4-hourly, or more frequently if high.
Strict Input/Output Charting & Daily Weights: This is vital for managing fluid balance.
First-Line Labs & Imaging:
Renal Profile (RP): Raised urea and creatinine (AKI).
Serum Electrolytes: Check for hyperkalemia (due to AKI) and hyponatremia (dilutional).
C3/C4 Complement: The key diagnostic test. Classic finding is Low C3 with Normal C4. C3 starts to recover in 2 weeks and normalises by 6-8 weeks.
Full Blood Count (FBC): May show normocytic anaemia (dilutional).
Evidence of GAS Infection:
ASOT (Anti-Streptolysin O Titer): Rises 1 week post-infection, peaks at 3-6 weeks. A single high titre is supportive. (Note: ASOT response is poor in post-pyoderma cases).
Anti-DNase B Titer: More sensitive for post-pyoderma infection.
(Throat/Skin Swab: Usually not helpful as the infection has often resolved).
Chest X-ray (CXR): Only if respiratory distress (look for cardiomegaly, pulmonary edema).
Confirmatory / Gold Standard:
Renal Biopsy: Not routinely done. Reserved for atypical cases:
Severe AKI / RPGN.
Nephrotic-range proteinuria.
Normal C3 level (rules out PSGN).
Failure of C3 to normalise after 8 weeks.
Failure of haematuria/proteinuria to resolve after 6-12 months.
(If done, biopsy shows: LM -> Diffuse proliferative GN. IF -> Granular "starry sky" IgG and C3 deposits. EM -> Subepithelial "humps").
VII. Staging & Severity Assessment
Severity is assessed clinically based on the degree of fluid overload, hypertension, and renal impairment.
Mild: Asymptomatic haematuria/proteinuria, no edema, normotensive. (Managed outpatient).
Moderate (Typical): Acute nephritic syndrome (edema, gross haematuria, HTN), mild-moderate AKI. (Requires admission).
Severe: Any of the following, requiring HDU/PICU monitoring:
Oliguric/anuric AKI.
Severe hypertension / Hypertensive emergency.
Significant fluid overload (e.g., pulmonary edema).
VIII. Management Plan
A. Principle of Management: This is a self-limiting disease. Management is entirely supportive and focuses on complications.
Control hypertension.
Manage fluid overload.
Monitor and manage AKI.
B. Immediate Stabilisation (The ABCDE Plan):
(As per Red Flags section)
A/B: High-flow O2 if respiratory distress. Sit patient upright.
C: Secure IV access.
Hypertensive Emergency: IV Labetalol or IV Hydralazine (refer to Paediatric Protocol for dosing).
Pulmonary Edema: STAT IV Furosemide (1-2 mg/kg/dose).
D: Seizure management (if hypertensive encephalopathy), check GCS, check electrolytes.
E: Monitor temperature.
C. Definitive Treatment (The Ward Round Plan):
1. Antibiotics:
Purpose: To eradicate nephritogenic GAS carriage from the pharynx/skin to prevent spread to others. This does NOT alter the course of the glomerulonephritis itself.
Regimen (as per Paediatric Protocol):
IM Benzathine Penicillin (single dose, weight-based).
OR Oral Penicillin V (phenoxymethylpenicillin) for 10 days.
(Use Erythromycin if true penicillin allergy).
2. Fluid & Salt Management (The Core Treatment):
Fluid Restriction: CRUCIAL. Calculate allowable intake based on:
Insensible Losses (approx. 400 ml/m²/day) + Previous Day's Urine Output.
Salt Restriction: Strict "No Added Salt" diet.
3. Diuretics:
For managing edema and hypertension.
Oral Furosemide: 1-2 mg/kg/dose, OD or BD. Dose can be titrated up.
4. Antihypertensives:
For persistent hypertension despite diuretics and salt/fluid restriction.
First-line: Calcium Channel Blocker (e.g., Oral Amlodipine or Nifedipine).
Avoid: ACE-inhibitors (e.g., Enalapril) are generally avoided in the acute phase due to AKI risk, but may be used by specialists for persistent proteinuria later.
5. Renal Replacement Therapy (Dialysis):
Rare. Indications (AEIOU):
Acidosis (severe, refractory).
Electrolyte (refractory hyperkalemia).
Intoxication (not relevant here).
Overload (refractory pulmonary edema).
Uremia (encephalopathy, pericarditis).
D. Long-Term & Discharge Plan:
Discharge Criteria:
Stable, well-controlled BP (may be on oral medication).
Resolving edema.
Improving renal function (Urea/Creatinine trending down).
No acute complications.
Follow-up (Paediatric Clinic):
Weekly for 1-2 weeks post-discharge (check BP, UFEME, RP).
Then monthly until urine is clear and BP is normal off medication.
Timeline of Resolution (Must know for counselling):
C3 Level: Normalises by 6-8 weeks.
Gross Haematuria: Resolves in 1-2 weeks.
Proteinuria: Resolves by 6 months.
Microscopic Haematuria: May persist for 1-2 years.
Advice: Continue low-salt diet until edema and hypertension are fully resolved. Prophylactic antibiotics are not required.
IX. Complications
Immediate (Acute Phase):
Hypertensive Encephalopathy/PRES: Action: Urgent BP control (IV antihypertensives).
Acute Pulmonary Edema: Action: IV Furosemide, O2, upright position.
Acute Kidney Injury (AKI): Action: Supportive fluid/electrolyte management. Dialysis if severe.
Hyperkalemia: Action: ECG monitoring, calcium gluconate (if ECG changes), insulin/dextrose, refer to renal team.
Long-Term:
Persistent Proteinuria/Haematuria: Action: Refer Paediatric Nephrology.
Chronic Kidney Disease (CKD): Very rare in children (<1%) but a significant risk in adults who get PSGN.
X. Prognosis
Children: Excellent. >95% make a full, complete recovery.
Adults: Prognosis is worse. Up to 20-50% may develop persistent renal abnormalities (e.g., CKD, persistent HTN).
Poor Prognostic Factors: Adult onset, severe AKI requiring dialysis, nephrotic-range proteinuria, crescentic GN on biopsy.
XI. How to Present to Your Senior
"Dr, I'm calling about [Patient Name], a [Age]-year-old [boy/girl] in [Ward/ED] admitted for acute nephritic syndrome, likely PSGN."
Situation: "He presented with periorbital edema and 'teh tarik' urine for [X] days, which started [Y] weeks after a [sore throat / skin infection]."
Background: "His vitals are: BP [Value] (which is on the [Number]th centile for his age/height), HR [Value], RR [Value]. He is [alert/drowsy]."
Assessment: "Findings are [e.g., bilateral pitting pedal edema to mid-shin, bibasal lung crepitations]. UFEME shows Blood 4+, Protein 2+. The Renal Profile shows Urea [Value], Creatinine [Value]. C3 is [low/pending]. My main concern is [e.g., severe hypertension / fluid overload with pulmonary edema]."
Recommendation: "I have started 4-hourly BP monitoring, a strict I/O chart, and fluid/salt restriction. I would like to start [e.g., oral Furosemide] and need your advice on [e.g., starting oral Amlodipine / giving IV Labetalol]."
XII. Summary & Further Reading
Top 3 Takeaways:
PSGN is an immune-complex nephritis that occurs 1-6 weeks after a GAS infection (pharyngitis or pyoderma).
Diagnosis is clinical (nephritic syndrome) + Low C3 + evidence of recent strep infection (ASOT/Anti-DNase B).
Management is purely supportive. Control BP and manage fluid overload. Antibiotics are for public health, not to treat the GN itself.
Key Resources:
Local Guideline: Malaysian Paediatric Protocols for Malaysian Hospitals (4th Edition). (Chapter on Acute Nephritis).
UpToDate: "Poststreptococcal glomerulonephritis".
Amboss: "Poststreptococcal glomerulonephritis".
