Nephrotic Syndrome is a clinical syndrome characterized by excessive protein loss in the urine due to increased permeability of the glomerular filtration barrier.
It is not a single disease , but a manifestation of various glomerular disorders affecting the kidney’s filtering unit (the glomerulus).
🔍 Core Diagnostic Characteristics (Classic Tetrad)
| Feature | Description |
|---|---|
| Proteinuria | >3.5 g/day in adults or >40 mg/m²/hour in children |
| Hypoalbuminemia | Serum albumin <2.5–3.0 g/dL |
| Edema | Generalized, pitting edema due to ↓ plasma oncotic pressure |
| Hyperlipidemia | ↑ serum cholesterol, triglycerides; also may see lipiduria (fatty casts, oval fat bodies in urine) |
Mnemonic: "P-H-E-M"
| Letter | Meaning |
|---|---|
| P | Proteinuria (>3.5 g/day) |
| H | Hypoalbuminemia |
| E | Edema (especially periorbital, pedal) |
| M | Hyperlipidemia (with lipiduria) |
Why Is Nephrotic Syndrome Important?
Though relatively rare, nephrotic syndrome is clinically significant because:
- It is a major cause of pediatric and adult referrals to higher-level care.
- Often chronic and prone to frequent relapses .
- Has a complex evaluation and management pathway .
- It is not a disease itself, but a syndrome resulting from various glomerular diseases .
🧠 Core Diagnostic Features (Mnemonic: P-HEM)
- Proteinuria >3.5 g/day
- Hypoalbuminemia
- Edema (generalized, pitting)
- Hyperlipidemia (↑ triglycerides, ↑ cholesterol)
📌 Pathognomonic : Massive proteinuria is the hallmark and the initiating feature.
🧬 Pathophysiology
The glomerulus acts as a charge- and size-selective barrier :
- Fenestrated endothelium
- Glomerular basement membrane (GBM)
- Podocyte slit diaphragms
In nephrotic syndrome:
- Damage to the GBM and podocytes increases permeability → protein loss in urine.
- Loss of negative charge selectivity (e.g., due to decreased heparan sulfate) allows albumin and other proteins to pass.
🔬 Key Molecular Players:
- Albumin : Main protein lost; smallest major plasma protein.
- Savin factor (FSGS): Circulating permeability factor increasing GBM permeability.
🧪 Consequences of Proteinuria
| Effect | Mechanism | Clinical Impact |
|---|---|---|
| ↓ Oncotic Pressure | Loss of albumin | Edema, hypovolemia |
| RAAS Activation | ↓ Renal perfusion | Sodium/water retention |
| ↓ IgG, factor B | Urinary loss | Immunosuppression, ↑ infection risk |
| ↓ Transferrin, Vitamin D–binding protein | Urinary loss | Iron-deficiency anemia, hypocalcemia |
| ↓ Antithrombin III | Urinary loss | Hypercoagulability , risk of thromboembolism |
| ↑ Hepatic Lipogenesis | Compensatory | Hyperlipidemia, lipuria |
🧬 Etiology and Classification
🔹 Primary (Idiopathic) Nephrotic Syndrome
- Minimal Change Disease (MCD) – most common in children
- Focal Segmental Glomerulosclerosis (FSGS)
- Membranous Nephropathy – common in adults
- Hereditary Nephropathies – e.g., Alport syndrome
🔹 Secondary Nephrotic Syndrome
- Diabetes Mellitus (most common cause in adults)
- Systemic Lupus Erythematosus
- Infections : Hep B, Hep C, HIV
- Malignancies : Hodgkin lymphoma
- Drugs : NSAIDs, gold, penicillamine, mercury
- Preeclampsia
- Amyloidosis and multiple myeloma
🧬 Complications
- Hypovolemia
- Acute kidney injury (AKI)
- Infections : Peritonitis, sepsis
- Thromboembolism : Renal vein thrombosis, DVT
- Malnutrition/protein deficiency
- Dyslipidemia
- Growth retardation in children
🩺 Signs and Symptoms
- Pitting edema : Starting periorbitally → generalized
- Ascites and pleural effusion
- Foamy urine (due to proteinuria)
- Features of complications :
- Hypotension, oliguria (hypovolemia)
- Fever (infection)
- Flank pain (renal vein thrombosis)
🧪 Diagnostic Workup
Urine Studies
- Urinalysis : Proteinuria (>3+), lipiduria (fatty casts)
- 24-hr Urine Protein or Spot protein/creatinine ratio
- Urine microscopy : Oval fat bodies ("Maltese cross" under polarized light)
Blood Tests
- Serum albumin : <2.5 g/dL
- Serum creatinine, urea : Check renal function
- Lipid profile : ↑ total cholesterol, ↑ triglycerides
- Electrolytes : Possible hyponatremia, hypocalcemia
Immunological/Serological Tests
- ANA, anti-dsDNA (SLE)
- Hepatitis B/C serologies
- HIV testing
- Serum protein electrophoresis (amyloidosis)
Imaging
- Renal ultrasound : Kidney size and echogenicity
- Renal biopsy : Indicated in adults, atypical cases, or steroid resistance
⚕️ Management
General Measures
- Low salt diet
- Normal protein intake (excess worsens proteinuria)
- Fluid restriction if edema severe
- Daily weight and urine output monitoring
1. Edema Management
- Salt restriction
- Diuretics :
- Furosemide (1–2 mg/kg/day)
- Spironolactone : Prevents hypokalemia
- Avoid in hypovolemic patients
- Albumin infusion + diuretic : If hypovolemia with edema
2. Immunosuppressive Therapy
- First-line : Prednisone 60 mg/m²/day for 4–6 weeks, then taper
- Steroid-resistant cases :
- Cyclophosphamide
- Calcineurin inhibitors : Cyclosporine, Tacrolimus
- Rituximab in refractory cases
3. Proteinuria Reduction
- ACE inhibitors : Captopril, Enalapril
- ARBs : Losartan, Valsartan
- These agents also reduce intraglomerular pressure and progression of kidney disease.
4. Infection Prophylaxis and Treatment
- Penicillin V : Prophylaxis for patients with ascites or recurrent infections
- Empirical antibiotics: 3rd generation cephalosporins + antistaphylococcal coverage
5. Thrombosis Prevention
- Encourage early ambulation
- Consider anticoagulation in high-risk patients
6. Hypertension
- Nifedipine or Hydralazine for short-term control
- Atenolol if needed
7. Psychosocial Support
- Chronic disease in children can affect mental health, growth, and school performance . Provide appropriate counseling and support.
🔍 Differential Diagnoses
- Acute glomerulonephritis
- Acute/chronic kidney disease
- Kwashiorkor
- Congestive heart failure
- Liver cirrhosis (hypoalbuminemia)
- Protein-losing enteropathy
📌 High-Yield Notes
- Minimal Change Disease is the most common cause in children—typically responds well to steroids.
- FSGS is the most common cause in adults with poor steroid response.
- Renal vein thrombosis is a classic complication of nephrotic syndrome.
- Avoid nephrotoxic drugs (e.g., NSAIDs, aminoglycosides).
- Use biopsy to differentiate cause in adults or steroid non-responders.
