Glomerulonephritis
DEFINITION
Glomerulonephritis is immunologically mediated inflammation of renal glomeruli.
AETIOLOGY
There are many different types of glomerulonephritis with differing aetiologies. Some types of glomerulonephritis are ascribed to deposition of antigen–antibody immune complexes in the glomeruli that lead to inflammation and activation of complement and coagulation cascades. The immune complexes may either form within the glomerulus (more commonly) or be deposited from the circulation. The antigens in the immune complexes are often unknown but may occasionally be associated with the following:
Infection: Bacterial: Streptococcus viridans, group A b-haemolytic streptococci, staphylococci, gonococci, Salmonella, syphilis.
Viral: Hepatitis B/C, HIV, measles, mumps, EBV, VZV, coxsackie.
Protozoal: Plasmodium malariae, schistosomiasis, filariasis.
Inflammatory/systemic diseases: SLE, systemic vasculitis, cryoglobulinaemia.
Drugs: Gold, penicillamine.
Tumours:
Classified based on the site of nephron pathology and its distribution.
Minimal-change glomerulonephritis: Normal appearance on light microscopy. Electron microscopy: Loss of epithelial foot processes.
Membranous glomerulonephritis: Thickening of GBM from immune complex deposition.Associated with Goodpasture’s syndrome.
Membranoproliferative glomerulonephritis (MPGN): Thickening of GBM, mesangial cell proliferation and interposition.
Type 1: Subendothelial immune complex deposits and reduplication of GBM.
Type 2: Dense intramembranous deposits (stain only for C3).
Focal segmental glomerulosclerosis: Glomerular scarring. Associated with HIV.
Focal segmental proliferative glomerulonephritis: Mesangial and endothelial cell proliferation. ‘Focal’ refers to involvement of some of the glomeruli, ‘segmental’ refers to involvement of parts of individual glomeruli.
Diffuse proliferative glomerulonephritis: Same as above but affects all glomeruli.
IgA nephropathy: Mesangial cell proliferation and mesangial IgA and C3 deposits.
Crescentric glomerulonephritis: Crescent formation by macrophages and epithelial cells,which fills up Bowman’s space.
Focal segmental necrotizing glomerulonephritis: Peripheral capillary loop necrosis (e.g. in Wegener’s granulomatosis, microscopic polyarteritis and other vasculitides). Often evolves into crescentric glomerulonephritis.
EPIDEMIOLOGY
Makes up to 25% of cases of chronic renal failure.
HISTORY
Haematuria, subcutaneous oedema, polyuria or oliguria, proteinuria. History of recent infection.
Symptoms of uraemia or renal failure (acute and chronic).
Cryoglobulins are immunoglobulins that precipitate in cold, and may be monoclonal or polyclonal. They can cause cutaneous vasculitis.
Goodpasture’s syndrome result from anti-GBM antibody that binds to an antigen in the basement membrane. The antibody also reacts with pulmonary capillary basement membrane and can cause pulmonary haemorrhage.
EXAMINATION
May present with the signs of the following:
- . hypertension;
- . proteinuria (<3 g/24 h);
- . haematuria (microscopic or macroscopic, especially IgA nephropathy);
- . nephrotic syndrome (usually for minimal-change glomerulonephritis in children and membranous glomerulonephritis in adults; see nephrotic syndrome);
- . nephritic syndrome (haematuria, proteinuria, subcutaneous oedema, oliguria, hypertension, uraemia);
- . renal failure (acute or chronic); and
- . partial lipodystrophy (loss of subcutaneous fat in MPGN type II).
INVESTIGATIONS
Blood:
FBC, U&E and creatinine, LFT (albumin), lipid profile, complement studies (C3, C4, C3 nephritic factor in MPGN), ANA, anti-double stranded DNA,ANCA, anti-GBM antibody, cryoglobulins if appropriate.
Urine:
Microscopy (dysmorphic RBCs, red-cell casts), 24-h collection: creatinine clearance,protein.
Imaging:
Renal tract ultrasound (to exclude other pathology).
Renal biopsy:
Light microscopy, electron microscopy, immunofluorescence microscopy.
Investigations for associated infections:
e.g. hepatitis B, hepatitis C or HIV serology.
MANAGEMENT
Fluid balance:
Monitor input/output and weight changes, avoid added salt and restrict fluid if there are signs of fluid overload or " BP.
Treatment of complications:
(see hypertension; renal failure, acute; renal failure, chronic,nephrotic syndrome).
Focal necrotizing glomerulonephritis, rapidly progressive crescentric glomerulonephritis,glomerulonephritis associated with SLE, primary vasculitides: Steroids, azathioprine,ciclosporin A, cyclophosphamide.
Consider plasma exchange, especially for severe disease affecting the basement membrane.
COMPLICATIONS
Pulmonary oedema: " Risk of hypertension, hypertensive encephalopathy. Renal failure. Complications of nephrotic syndrome. Pre-eclampsia in pregnancy.
PROGNOSIS
Minimal-change glomerulonephritis and post-infective diffuse proliferative glomerulonephritis mostly resolve.
Risk of CRF: Focal segmental sclerosis 50–75%; focal proliferative glomerulonephritis 25%; membranous glomerulonephritis 30%; MPGN >75%.
Poor prognostic factors: " Creatinine when first seen, " BP, persistent proteinuria.
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