Glomerulonephritis (GN) refers to a group of diseases causing inflammation of the glomeruli, leading to impaired kidney function. It is an important topic for the UKMLA, emphasizing classification, clinical presentation, investigations, and management.

Classification:

1. Based on Onset:

1. • Acute Glomerulonephritis: Rapid onset (e.g., post-infectious GN).
   • Rapidly Progressive Glomerulonephritis (RPGN): Rapid loss of kidney function.
   • Chronic Glomerulonephritis: Persistent inflammation leading to chronic kidney disease.

2. Based on Pathophysiology:

1. • Nephritic Syndrome: Haematuria, proteinuria (<3.5 g/24h), hypertension.
   • Nephrotic Syndrome: Heavy proteinuria (>3.5 g/24h), hypalbuminaemia, oedema.

Key Features of Acute Nephritic Syndrome:

1. Haematuria: Microscopic or macroscopic (cola-coloured urine).
2. Proteinuria: Usually sub-nephrotic range.
3. Hypertension: Due to fluid retention and activation of RAAS.
4. Oedema: Periorbital or peripheral.
5. Reduced GFR: Causes oliguria and azotaemia.

Causes:

1. Infectious Causes:

1. • Post-Streptococcal Glomerulonephritis (PSGN): Most common in children, following group A streptococcal throat or skin infection.
   • Infective Endocarditis-Associated GN.
   • Hepatitis B/C: Associated with membranoproliferative GN.

2. Autoimmune Causes:

1. • IgA Nephropathy (Berger’s Disease): Most common worldwide; gross haematuria post-URTI.
   • Goodpasture Syndrome: Anti-GBM antibodies; haemoptysis + GN.
   • Systemic Lupus Erythematosus (SLE): Lupus nephritis.
   • ANCA-Associated Vasculitis: Granulomatosis with polyangiitis (GPA), microscopic polyangiitis.

3. Others:

1. • Membranoproliferative GN: Often secondary to infections or autoimmune conditions.
   • Alport Syndrome: Genetic; associated with hearing and ocular abnormalities.

Investigations:

1. Urinalysis:

1. • Red cell casts (specific for GN).
   • Dysmorphic red blood cells (glomerular origin).
   • Proteinuria (sub-nephrotic in nephritic syndrome).

2. Blood Tests:

1. • Urea, creatinine: To assess renal function.
   • Complement levels (C3, C4): Low in PSGN, lupus nephritis, and MPGN.
   • ANCA: Positive in vasculitis.
   • Anti-GBM antibodies: Positive in Goodpasture syndrome.
   • Anti-streptolysin O (ASO) titre: Elevated in PSGN.
   • ANA, anti-dsDNA: Suggest lupus nephritis.

3. Imaging:

1. • Renal ultrasound: To rule out obstruction and assess kidney size.
   • CXR: For pulmonary-renal syndromes (e.g., Goodpasture).

4. Renal Biopsy:

1. • Gold standard to determine the underlying cause.
   • Histological patterns: Crescent formation (RPGN), mesangial proliferation (IgA nephropathy), or immune deposits.

Management:

1. General Measures:

1. • Blood pressure control: ACE inhibitors/ARBs.
   • Fluid restriction and diuretics for oedema.
   • Sodium restriction for hypertension.

2. Specific Treatments:

1. • Post-Streptococcal GN: Supportive (self-limiting); antibiotics if active infection.
   • IgA Nephropathy: ACE inhibitors/ARBs; steroids in severe cases.
   • Lupus Nephritis: Immunosuppression (steroids, mycophenolate, cyclophosphamide).
   • ANCA-Associated Vasculitis: High-dose steroids + cyclophosphamide/rituximab.
   • Goodpasture Syndrome: Plasmapheresis + steroids + cyclophosphamide.

3. Management of RPGN:

1. • Aggressive immunosuppression: Corticosteroids + cyclophosphamide/rituximab.
   • Plasmapheresis in anti-GBM disease or severe vasculitis.

4. Chronic GN:

1. • Slowing progression: BP control, proteinuria reduction, and treating the underlying cause.
   • Dialysis or transplantation in ESRD.

Complications:

1. Acute Kidney Injury (AKI): Particularly in RPGN.
2. Chronic Kidney Disease (CKD): Persistent damage and progression to ESRD.
3. Hypertension: Long-term renal damage.
4. Thromboembolic Events: Secondary to nephrotic-range proteinuria in some cases.

Key Exam Points for UKMLA:

• PSGN: Typically in children, low C3 levels, self-limiting.
• IgA Nephropathy: Recurrent hematuria post-URTI.
• Lupus Nephritis: Presents with systemic lupus signs, ANA/anti-dsDNA positive.
• Goodpasture Syndrome: Pulmonary hemorrhage and GN; anti-GBM antibodies.
• RPGN: Crescentic GN on biopsy, rapid loss of renal function.