NephrologyTier 1Disease (DEADMAN)

Acute and chronic glomerulonephritis - nephritic syndromes

Description

The nephritic syndrome - five features

Lesion is endothelial/inflammatory, on the blood side of the GBM -> leucocyte recruitment -> capillary wall breach
*RBC casts are the single most specific finding in nephrology* - they are formed only in the tubule, so they prove a glomerular source

The spectrum by tempo

	Course
Acute nephritic	Days-weeks, often self-limiting (PSGN)
RPGN	<3 months, crescentic - a renal emergency
Chronic GN	Years; incidental proteinuria/haematuria, small kidneys, hypertension

IgA nephropathy is the commonest glomerulonephritis worldwide and the commonest nephritic presentation in Australia
ANCA vasculitis is the commonest cause of RPGN; peak age >55
PSGN is now rare in urban Australia but remains common in remote Aboriginal and Torres Strait Islander communities
Lupus nephritis: 40-50% of SLE, more severe in Asian, African and Aboriginal and Torres Strait Islander populations

Causes of the nephritic syndrome

IgA nephropathy - mesangial galactose-deficient IgA1 complexes; synpharyngitic haematuria; normal complement
IgA vasculitis (Henoch-Schonlein purpura) - the systemic form; purpura, arthritis, abdominal pain, identical renal lesion
Post-infectious/post-streptococcal GN - 10-21 day latency, low C3, subepithelial humps
Lupus nephritis - class III/IV proliferative (class V is membranous and nephrotic); 'full house' IF, low C3 AND C4
Pauci-immune (ANCA) GN - GPA, MPA, EGPA, renal-limited; negative IF, normal complement
Anti-GBM disease - linear IgG; pulmonary-renal syndrome
MPGN / C3 glomerulopathy - mixed nephritic-nephrotic, tram-track double contours; low C3
Cryoglobulinaemic GN - hepatitis C; C4 disproportionately low
Infective endocarditis and shunt nephritis - low C3
Thrombotic microangiopathy - HUS, TTP, aHUS, malignant hypertension, scleroderma renal crisis, APS

Complement is the fastest discriminator

Low C3 + low C4	Low C3, normal C4	Normal complement
SLE, cryoglobulinaemia, shunt nephritis, endocarditis	PSGN, C3 glomerulopathy, some MPGN	IgA nephropathy, IgA vasculitis, ANCA vasculitis, anti-GBM

Confirm glomerular bleeding

Phase-contrast microscopy: dysmorphic RBCs, acanthocytes (>5% is significant), RBC casts
Non-glomerular haematuria (stones, tumour, infection) gives isomorphic RBCs, clots and no casts, and needs urological rather than renal work-up

Distinguish nephritic from nephrotic

Overlap is common: IgA nephropathy, MPGN, lupus and myeloma can present with either or both

Serology - send all of it at once

Renal biopsy

Indicated in nearly every adult nephritic presentation, and urgently if the creatinine is rising
Exception: a child with textbook PSGN - low C3, clear latency, improving by 4 weeks

Red flags for RPGN

Creatinine rising over days to weeks, oliguria, haemoptysis, systemic vasculitic features
*Suspicion of RPGN mandates same-day serology and next-day biopsy*

Immediate - in every nephritic presentation

Assess for RPGN: is the creatinine rising? Is there pulmonary haemorrhage?
Blood pressure and volume - salt restriction, loop diuretic, then antihypertensives
Stop nephrotoxins; monitor K+ and acid-base
Send the full serology panel before starting steroids where possible

Disease-specific

IgA nephropathy - maximal RASi + SGLT2i for everyone; targeted-release budesonide or reduced-dose systemic corticosteroids, or sparsentan, for persisting high-risk proteinuria. Target proteinuria <0.5 g/day, ideally <0.3
PSGN - supportive only; antibiotics if ongoing infection; no immunosuppression unless crescentic
ANCA vasculitis - glucocorticoid (rapid taper) + rituximab or cyclophosphamide; avacopan as a glucocorticoid-sparing option; plasma exchange only if creatinine >300, dialysis-requiring, or alveolar haemorrhage with hypoxaemia
Anti-GBM - plasma exchange + steroid + cyclophosphamide, urgently
Lupus class III/IV - glucocorticoid + MPAA or low-dose IV cyclophosphamide, or triple therapy with belimumab or a CNI; hydroxychloroquine in all
Cryoglobulinaemic GN - direct-acting antivirals for hepatitis C; rituximab +/- plasma exchange if severe
C3 glomerulopathy - RASi; complement inhibition (iptacopan, pegcetacoplan) emerging
Endocarditis-associated GN - treat the infection; immunosuppression is harmful

Supportive in all chronic GN

Maximal ACEi/ARB, SGLT2i, BP <120 systolic, statin, sodium restriction
Vaccination; PJP prophylaxis on combination immunosuppression; bone protection; fertility counselling before cyclophosphamide

URTI or gastroenteritis - synpharyngitic IgA nephropathy
Streptococcal pharyngitis and pyoderma; scabies - PSGN
SLE, ANCA vasculitis, IgA vasculitis, cryoglobulinaemia
Hepatitis B (membranous, PAN), hepatitis C (MPGN, cryoglobulinaemia), HIV
Infective endocarditis, ventriculoatrial shunt, deep abscess, osteomyelitis
Cirrhosis, coeliac disease, IBD, ankylosing spondylitis - secondary IgA deposition
Smoking and hydrocarbon exposure - anti-GBM
Malignancy, drugs (hydralazine, propylthiouracil, levamisole-adulterated cocaine)

Prognosis is set by the lesion, the eGFR at presentation, and the degree of interstitial fibrosis on biopsy - not by the severity of the haematuria
PSGN in children: >95% complete recovery; adults far worse (30-50% residual impairment)
IgA nephropathy: 20-40% ESKD at 20 years - slow but relentless
RPGN: ~50% ESKD; mortality from pulmonary haemorrhage and sepsis
Lupus nephritis: 10-30% ESKD at 15 years; complete renal response at 12 months predicts long-term survival

What to monitor

eGFR, UPCR and BP 3-6 monthly - proteinuria is the modifiable target in every lesion
Disease-specific serology: C3 (must normalise by 12 weeks in PSGN), anti-dsDNA, ANCA titre, anti-GBM titre
Persistent isolated microscopic haematuria with normal eGFR and proteinuria <0.5 g/day needs surveillance, not treatment - annual BP, eGFR, UACR
Treatment toxicity: infection (the leading cause of early death), cyclophosphamide-related malignancy and infertility, steroid complications

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