Doctors Revision

Renal & Urinary System

Acute Glomerulonephritis (AGN)

Acute inflammation of the glomeruli (filtering units) of the kidneys, often triggered by an immune response to a preceding infection (most commonly Group A Streptococcus). Characterized by haematuria, proteinuria, oedema, and hypertension.

Also known as: AGN, Nephritic Syndrome (often implied), Post-Streptococcal Glomerulonephritis

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Referral and warning signs

When to refer

Referral to hospital (H/RR) generally required for initial diagnosis and management due to risk of AKI, hypertension, and fluid overload. Referral to Nephrologist needed for: Severe AKI requiring dialysis. Persistent hypertension or proteinuria >3-6 months. Atypical features (normal C3, rapidly progressive decline, systemic symptoms suggesting other causes). Need for kidney biopsy.

Red flags

  • Anuria or severe oliguria
  • Severe hypertension / Hypertensive encephalopathy (headache, confusion, seizures)
  • Signs of pulmonary oedema (severe dyspnoea)
  • Rapidly worsening renal function
  • Signs suggesting systemic vasculitis or lupus

Signs and symptoms

  • Haematuria: Gross (visible - red, brown, 'tea-coloured' urine) or microscopic.
  • Oedema: Often starting periorbitally (puffy eyes), may become generalised.
  • Hypertension: Often acute onset, may be severe.
  • Oliguria (reduced urine output).
  • Proteinuria (usually non-nephrotic range, <3.5g/day).
  • Malaise, lethargy, anorexia.
  • Flank or abdominal pain.
  • Symptoms related to hypertension: Headache, visual disturbances, vomiting, seizures (hypertensive encephalopathy).
  • Symptoms of fluid overload: Dyspnoea (pulmonary oedema).
  • Recent history (1-5 weeks prior) of sore throat (pharyngitis) or skin infection (impetigo/pyoderma) - suggestive of post-streptococcal GN.

Risk factors

  • Recent Group A Beta-Haemolytic Streptococcal (GAS) infection (pharyngitis or impetigo) - Post-streptococcal GN (PSGN).
  • Other infections (less common): Bacterial (Staph endocarditis), Viral (Hepatitis B/C, HIV, CMV), Parasitic (Malaria).
  • Systemic autoimmune diseases: Systemic Lupus Erythematosus (SLE - Lupus nephritis), IgA nephropathy, Vasculitis (e.g., ANCA-associated).

Diagnosis

Clinical assessment

Suspect in a child/adolescent presenting with acute onset haematuria, oedema, and hypertension, often following a recent throat/skin infection. Assess fluid status, BP, signs of complications. Differential diagnosis: Other causes of haematuria/oedema/hypertension (Nephrotic syndrome, UTI/pyelonephritis, IgA nephropathy, other kidney diseases, heart failure).

Investigations

  • Urinalysis: Key test. Shows haematuria (RBCs), proteinuria, red blood cell casts (pathognomonic for glomerular bleeding).
  • Blood tests:
  • - Urea, Creatinine, Electrolytes: Assess renal function (AKI often present).
  • - Complement levels (C3, C4): C3 often low in PSGN, normalizes over weeks. Persistently low C3 or low C4 suggests other causes (e.g., SLE, MPGN).
  • - Evidence of recent Strep infection: Anti-Streptolysin O (ASO) titre (elevated after pharyngitis), Anti-DNase B titre (elevated after skin infection).
  • - Autoimmune screen (ANA, ANCA, etc.) if systemic disease suspected.
  • - Viral serology (HBV, HCV, HIV) if indicated.
  • Kidney Ultrasound: Usually normal size kidneys, rule out other pathology.
  • Kidney Biopsy: Reserved for atypical cases (e.g., severe/rapidly progressive GN, persistent abnormalities, suspected non-PSGN cause).

Diagnostic criteria

Clinical presentation (haematuria, oedema, hypertension) + Urinalysis findings (RBCs, protein, RBC casts) +/- Evidence of preceding Strep infection +/- Low C3 complement level.

Management

Non-pharmacological management

  • Supportive Care:
  • - Fluid Restriction: If oliguria and oedema present. Match intake to output + insensible losses.
  • - Sodium Restriction: <2g/day.
  • - Potassium Restriction: If oliguria/hyperkalaemia.
  • - Protein Restriction: Moderate restriction if significant renal impairment.
  • - Bed Rest: During acute phase may be helpful.
  • - Monitor: Daily weight, fluid balance (I/O chart), BP (frequently).

Pharmacological treatment

  • Treat Underlying Infection (if still present):
  • - Post-streptococcal: Eradicate GAS even if throat culture negative. Phenoxymethylpenicillin (Pen V) 500mg QID (Adult) / 10-20mg/kg/dose QID (Child) for 10 days. OR Amoxicillin. OR Benzathine Penicillin G single IM dose. Erythromycin if penicillin allergic.
  • Manage Hypertension:
  • - Loop Diuretics: Furosemide 1-2mg/kg IV/PO (Adult dose 40-80mg) for fluid overload/hypertension.
  • - Vasodilators: Nifedipine (Calcium Channel Blocker) 10-20mg PO PRN/TID (Child dose specialist). Hydralazine IV for hypertensive emergency.
  • - ACE inhibitors/ARBs: May be used cautiously for persistent hypertension/proteinuria after acute phase resolves (specialist).
  • Immunosuppression (Specialist management): Generally NOT used for typical PSGN. Required for other specific types of rapidly progressive GN (e.g., lupus nephritis, ANCA vasculitis) based on biopsy findings.

Monitoring

Monitor BP, fluid balance, weight, urine output closely. Monitor renal function (Urea, Creatinine) and electrolytes periodically. Monitor urinalysis for resolution of haematuria/proteinuria (may take weeks/months). Monitor complement levels (C3 should normalize within 6-8 weeks in PSGN).

Complications

  • Acute Kidney Injury (AKI) / Renal failure
  • Hypertensive encephalopathy / Seizures
  • Pulmonary oedema / Heart failure (due to fluid overload/hypertension)
  • Hyperkalaemia
  • Chronic Kidney Disease (rare after typical childhood PSGN, higher risk in adults or atypical forms)

Prevention

  • Prompt diagnosis and treatment of Group A Streptococcal pharyngitis and skin infections with appropriate antibiotics.

Patient education

  • Explain AGN as kidney inflammation often following infection.
  • Reassurance that prognosis is generally good, especially in childhood PSGN.
  • Importance of fluid/salt restriction during acute phase.
  • Need for blood pressure monitoring and treatment.
  • Explanation of monitoring tests (urine, blood).
  • Importance of completing antibiotic course if prescribed for Strep infection.
  • Need for long-term follow-up to ensure resolution.

Uganda-specific notes

Post-streptococcal GN is the most common type, often following skin infections (impetigo). Malaria can also cause a form of GN. Diagnosis often relies on clinical presentation and urinalysis due to limited availability of complement/ASO titres/biopsy. Management focuses on supportive care, fluid/salt restriction, and BP control.

References

  • Uganda Clinical Guidelines (UCG) 2023

    Chapter 7, Section 7.1.4

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