What are the distinguishing features, diagnostic workup, and initial management for nephrotic versus nephritic syndrome?

Distinguishing Nephrotic from Nephritic Syndrome

Nephrotic syndrome presents with heavy proteinuria (>3.5 g/day), hypoalbuminemia (<3.0 g/dL), and edema, while nephritic syndrome presents with hematuria, proteinuria (typically <3.5 g/day), hypertension, and acute kidney injury—these are fundamentally different clinical entities requiring distinct diagnostic and therapeutic approaches 1.

Key Clinical Distinctions

Nephrotic Syndrome Features

• Proteinuria >3.5 g/24 hours (often >10 g/day in severe cases)
• Serum albumin <3.0 g/dL
• Peripheral edema (often severe, anasarca)
• Hyperlipidemia
• Thrombotic complications (due to urinary loss of anticoagulant proteins)
• Foamy urine appearance
• Normal or near-normal kidney function initially 1, 2

Nephritic Syndrome Features

• Hematuria (often with RBC casts)
• Proteinuria (typically <3.5 g/day, though overlap exists)
• Acute kidney injury with rising creatinine
• Hypertension (often severe)
• Oliguria
• Edema (less severe than nephrotic)
• Carries poorer prognosis than nephrotic syndrome 1, 3

Critical pitfall: Some conditions can present with "mixed" nephrotic-nephritic features (e.g., lupus nephritis, membranoproliferative GN), where both heavy proteinuria and active urinary sediment coexist 4.

Diagnostic Workup Algorithm

Initial Laboratory Evaluation

1. Urine studies:

   • 24-hour urine protein quantification (gold standard when considering immunosuppression) 5
   • First morning protein-creatinine ratio (PCR) for monitoring, especially in children 5
   • Urinalysis with microscopy: look for acanthocytes and cellular casts (diagnostic for glomerulonephritis) 4

2. Serum studies:

   • Creatinine/eGFR (decreased in nephritic, often preserved in nephrotic)
   • Albumin (low in nephrotic, normal/mildly low in nephritic)
   • Lipid panel (elevated in nephrotic)
   • Complement levels (C3, C4)
   • Serologies: ANA, anti-dsDNA, ANCA, anti-GBM, hepatitis panel, HIV
   • PLA2R antibody (for membranous nephropathy) 5

Kidney Biopsy Indications

Kidney biopsy is the gold standard for diagnosis 5. However, treatment may proceed without biopsy in specific circumstances:

• Biopsy indicated when:

  • Diagnosis uncertain
  • Proteinuria ≥0.5 g/day in suspected primary glomerular disease
  • Result will modify treatment decisions
  • Prognostic information needed 5, 6

• May treat without biopsy:

  • PLA2R+ membranous nephropathy with normal eGFR
  • ANCA+ vasculitis (MPO or PR3 positive)
  • Anti-GBM disease
  • Well-characterized genetic FSGS in families 5

Biopsy adequacy requires: ≥8-10 glomeruli for light microscopy, immunofluorescence (IgG, IgA, IgM, C3, C4, C1q), and electron microscopy 5.

Initial Management Framework

Nephrotic Syndrome Management

For primary nephrotic syndrome (e.g., minimal change disease, FSGS), immunosuppression is indicated only with nephrotic-range proteinuria and clinical nephrotic syndrome 7, 8.

Minimal Change Disease (most common in children, 10-15% in adults):

• Prednisone 1 mg/kg/day (max 80 mg) or 2 mg/kg alternate-day (max 120 mg)
• Continue high-dose for minimum 4 weeks, maximum 16 weeks until complete remission
• Taper slowly over 6 months after remission 9, 7
• For contraindications to steroids (diabetes, psychiatric disease, osteoporosis): consider CNIs as first-line 9

Primary FSGS (requires nephrotic syndrome for treatment):

• Same steroid regimen as MCD: 1 mg/kg/day (max 80 mg) for 4-16 weeks 8, 9
• Critical distinction: Must differentiate primary from secondary FSGS—immunosuppression only for primary FSGS with proteinuria >3.5 g/day AND albumin <3.0 g/dL 10, 8
• Evaluate for secondary causes (viral, drug-induced, obesity, genetic) before starting immunosuppression 10
• Genetic testing recommended for familial disease, syndromic features, or steroid-resistant FSGS 10
• For steroid-resistant FSGS: cyclosporine 3-5 mg/kg/day for 4-6 months minimum, continue 12 months if response 9

Membranous Nephropathy:

Start immunosuppression only when:

• Proteinuria persistently >4 g/day for 6 months despite conservative therapy, OR
• Severe/disabling nephrotic symptoms, OR
• Creatinine risen 30% within 6-12 months with eGFR >25-30 mL/min 9

Treatment: 6-month course of alternating monthly cycles of oral/IV corticosteroids and oral alkylating agents 9

Nephritic Syndrome Management

Nephritic syndrome is a nephrological emergency requiring urgent diagnosis and treatment 4.

Rapidly Progressive Glomerulonephritis:

• Immediate kidney biopsy (unless contraindicated or serologies diagnostic)
• Empiric immunosuppression may be started before biopsy if ANCA+ or anti-GBM+ 5
• Treatment depends on underlying cause (ANCA vasculitis, anti-GBM, lupus nephritis)

Post-infectious GN (most common nephritic in children):

• Supportive care: blood pressure control, diuretics, sodium restriction
• No immunosuppression indicated
• Monitor for resolution (hematuria may persist weeks to months) 1, 3

IgA Nephropathy (most common primary GN worldwide):

• For proteinuria >0.5 g/day: behavioral modifications, BP goal <120/70 mmHg, RAS inhibition
• Consider targeted-release budesonide, systemic glucocorticoids, or iptacopan for persistent proteinuria despite optimal supportive care 6

Universal Supportive Measures (Both Syndromes)

1. Blood pressure control: Target <120/70 mmHg with RAS inhibition (ACEi/ARB) 6
2. Sodium restriction: <2 g/day 6
3. Diuretics for edema management
4. Anticoagulation consideration in nephrotic syndrome with albumin <2.0-2.5 g/dL (high thrombotic risk) 9
5. Avoid statins and ACEi/ARBs solely for proteinuria reduction in initial MCD episode 9

Common pitfall: Do not delay biopsy in adults with nephrotic syndrome assuming minimal change disease—adults have much higher rates of FSGS and membranous nephropathy requiring different management 7.