Difference between nephritis and nephrotic syndrome
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Nephritis vs. Nephrotic Syndrome
These are the two major clinical syndromes of glomerular disease, with distinct pathophysiology, presentations, and causes.
Core Distinction
| Feature | Nephrotic Syndrome | Nephritic Syndrome (Nephritis) |
|---|---|---|
| Primary defect | Increased glomerular permeability to protein | Glomerular inflammation → reduced GFR |
| Onset | Insidious | Abrupt |
| Proteinuria | Massive (≥3.5 g/day in adults) | Mild–moderate (subnephrotic) |
| Hematuria | Absent or mild | Prominent (brown/cola-coloured urine) |
| RBC casts | Absent | Present — hallmark finding |
| Edema | Severe (++++) | Mild–moderate (++) |
| Blood pressure | Normal | Raised |
| Jugular venous pressure | Normal or low | Raised |
| Serum albumin | Low (hypoalbuminaemia) | Normal or slightly reduced |
| Azotemia/↓GFR | Late/mild | Early and prominent |
— Comprehensive Clinical Nephrology, 7th Edition, Table 16.4
Nephrotic Syndrome
Pathophysiology
The primary lesion is in the podocytes or glomerular basement membrane (GBM), causing a marked increase in permeability to protein. The resulting massive protein loss drives the characteristic constellation:
- Massive proteinuria (>3.5 g/day) → the defining feature
- Hypoalbuminaemia → reduced oncotic pressure → oedema
- Hyperlipidaemia (serum cholesterol can exceed 500 mg/dL) — compensatory hepatic lipoprotein synthesis; highly atherogenic profile
- Lipiduria — "oval fat bodies" and fatty casts in urine
- Hypercoagulability — loss of anticoagulant proteins (antithrombin III, protein C/S) + enhanced platelet aggregation → risk of DVT, renal vein thrombosis, pulmonary embolism (risk especially high in membranous nephropathy; events increase markedly when albumin <2 g/dL)
Causes (primary glomerular diseases)
| Disease | Key Associations |
|---|---|
| Minimal change disease (MCD) | Most common in children; podocyte effacement; responds to steroids |
| Focal segmental glomerulosclerosis (FSGS) | Most common in adults; obesity, HIV, heroin |
| Membranous nephropathy | Adults; anti-PLA2R antibody; associated with malignancy, HBV, drugs |
| Membranoproliferative GN | May present as nephrotic, nephritic, or mixed |
| Diabetic nephropathy | Secondary; most common secondary cause worldwide |
| Amyloidosis, SLE | Secondary causes |
Nephritic Syndrome (Nephritis)
Pathophysiology
The primary lesion is glomerular inflammation — proliferation of glomerular cells and infiltration by inflammatory leucocytes. This injures the capillary walls, causing:
- Blood to leak into urine → haematuria + RBC casts
- Reduced GFR → oliguria, azotemia, fluid retention
- Sodium and water retention → hypertension (also from renin release by ischaemic kidneys)
- Proteinuria is present but usually subnephrotic (albumin is thus relatively preserved)
The classic example is post-streptococcal GN in children: typically appears 1–4 weeks after group A β-haemolytic streptococcal pharyngitis or impetigo. Immune complexes containing streptococcal antigens (especially SpeB) deposit in glomeruli → complement activation → inflammatory response.
Causes
| Disease | Key Features |
|---|---|
| Post-streptococcal GN | Commonest classic nephritis; low complement (C3) |
| IgA nephropathy (Berger's disease) | Most common GN worldwide; follows mucosal infections |
| Lupus nephritis (class III/IV) | ANA, anti-dsDNA positive |
| ANCA-associated vasculitis | pauci-immune; crescentic GN; rapidly progressive |
| Anti-GBM disease (Goodpasture's) | Linear IgG deposits; pulmonary haemorrhage |
| Rapidly progressive (crescentic) GN | Crescents in Bowman's space; medical emergency |
— Robbins, Cotran & Kumar Pathologic Basis of Disease; Comprehensive Clinical Nephrology, 7th Edition
Key Memory Anchors
- Nephrotic = protein loss is the story → "frothy urine, puffy face, low albumin, high cholesterol"
- Nephritic = inflammation is the story → "haematuria, RBC casts, hypertension, oliguria"
- RBC casts = pathognomonic of glomerular bleeding (nephritis)
- Some diseases (e.g., membranoproliferative GN, lupus nephritis) can produce a mixed picture
"The distinction between typical nephrotic syndrome and nephritic syndrome is usually straightforward on clinical and laboratory grounds… However, the classification systems are imperfect, and patients with certain glomerular disease patterns… may present with nephrotic syndrome, nephritic syndrome, or a combination of both syndromes." — Comprehensive Clinical Nephrology, 7th Edition, p. 243
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