Glomerulonephritis

A relatively uncommon cause of AKI (~5% of hospitalised AKI cases) — inflammation in the glomerulus causing kidney dysfunction over days to weeks, which may or may not resolve. Multiple subtypes exist with different causes and associations.

Classification by mechanism

Mechanism	Examples
Immune complex deposition	IgA nephropathy (see iga-nephropathy.md), infection-related GN (see post-strep-glomerulonephritis.md), lupus nephritis, cryoglobulinaemic GN (from hepatitis C)
Anti-GBM antibody-associated	Goodpasture syndrome (with pulmonary haemorrhage)
Pauci-immune (ANCA-positive)	Small vessel vasculitis — see vasculitis.md
Other	C3 glomerulopathy, hypertensive emergency, monoclonal immunoglobulin-mediated GN

Presentation

Non-specific history. Examination may show dependent oedema and hypertension.

Investigations

• AKI on UECs — creatinine rises over days to months
• Haematuria with dysmorphic or normal red cells
• Red cell casts on microscopy — pathognomonic when present, but not required for diagnosis
• Proteinuria may be present, usually <3 g/day

To determine the specific cause:

• ASO titre → post-streptococcal GN
• Anti-GBM antibody → anti-GBM GN
• ANCA → pauci-immune GN
• ANA → lupus

Kidney biopsy is required for a definitive diagnosis.

Management

Refer to nephrology. May need high-dose steroids, rituximab, cyclophosphamide, or plasma exchange depending on the underlying cause.