Nephritic Syndrome
Pathophysiology
Glomerular inflammation (glomerulonephritis) leading to haematuria, proteinuria, and renal impairment
Immune-mediated injury to glomerular capillaries, resulting in increased permeability and reduced glomerular filtration
Causes
Common causes:
Post-infectious GN (e.g., post-streptococcal glomerulonephritis, PSGN)
IgA nephropathy (Berger’s disease) – most common, especially in young males of Asian descent, typically 1–2 days post-URTI
Small vessel vasculitis (ANCA-associated):
Granulomatosis with polyangiitis (Wegener’s)
Microscopic polyangiitis
Anti-GBM disease (Goodpasture’s syndrome) – associated with pulmonary haemorrhage
Other causes:
SLE nephritis (can cause both nephritic and nephrotic syndrome)
Membranoproliferative GN (MPGN) – rare, often secondary to autoimmune or chronic infections
Presentation
Haematuria – macroscopic (tea/coca-cola coloured urine) or microscopic
Hypertension – due to fluid retention and renal impairment
Oedema – often periorbital and lower limb
Acute kidney injury (AKI) – rising creatinine, reduced eGFR
Proteinuria – typically <3.5 g/day (often <1.5 g/day), ACR/PCR <300 mg/mmol
Diagnosis
Initial investigations:
Bloods:
UEC (assess renal function)
FBC (anaemia of chronic disease, infection markers)
Complement levels (low in PSGN, lupus nephritis)
ASOT (post-streptococcal GN)
ANA (SLE), ANCA (vasculitis), anti-GBM (Goodpasture’s)
Urine tests:
Urinalysis – haematuria, proteinuria
Urine microscopy: Red cell casts (specific for glomerular pathology)
Urine PCR/ACR (quantify proteinuria) or 24-hour urine protein
Urine MCS to exclude infection
Imaging:
Renal ultrasound – assess kidney size, rule out obstruction
Renal biopsy – required for definitive diagnosis
Urine ACR reference range:
Normal: Male <2.5 mg/mmol, Female <3.5 mg/mmol
Microalbuminuria: Male 2.5–25 mg/mmol, Female 2.5–35 mg/mmol
Macroalbuminuria: Male >25 mg/mmol, Female >35 mg/mmol
Nephrotic range: >300 mg/mmol
Treatment
General measures:
BP control: Aim for <130/80 mmHg
ACE inhibitors/ARBs if proteinuria present (reduce glomerular pressure and proteinuria)
Salt and fluid restriction if oedema present
Diuretics (loop diuretics for volume overload)
Immunosuppression:
Corticosteroids (especially for IgA nephropathy, SLE nephritis, or vasculitis)
Cyclophosphamide/MMF (vasculitis or severe autoimmune causes)
Specific management:
PSGN: Supportive care (self-limiting in most cases), antibiotics for active infection
IgA nephropathy: BP control, fish oil, consider steroids if progressive disease
ANCA-associated vasculitis: High-dose steroids and cyclophosphamide or rituximab
Goodpasture’s syndrome: Plasmapheresis, steroids, and cyclophosphamide
Notes
IgA nephropathy is the most common cause of primary glomerulonephritis, often seen post-URTI or GI infection
Think haematuria workup when considering differentials
If urine protein is ≥4 g/day with only mild haematuria, consider nephrotic syndrome instead
Early renal biopsy is key in guiding treatment for progressive or uncertain cases
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