Nephrotic vs Nephritic Syndrome
Nephrotic: massive proteinuria (>3.5g/day), hypoalbuminemia, edema, hyperlipidemia. Nephritic: hematuria, RBC casts, HTN, mild proteinuria, ↓ GFR. The distinction guides workup and differential.
🔍 Overview
Key Distinction
| Feature | Nephrotic Syndrome | Nephritic Syndrome |
|---|---|---|
| Proteinuria | > 3.5 g/day (massive) | < 3.5 g/day (mild-moderate) |
| Hematuria | Absent or mild | Present -dysmorphic RBCs, RBC casts |
| Edema | Severe (periorbital, anasarca) | Mild-moderate |
| Albumin | ↓↓ (< 3 g/dL) | Normal or mildly ↓ |
| Lipids | ↑↑ Hyperlipidemia | Normal |
| Complement | Normal | Low in some (post-strep, lupus, MPGN) |
| BP | Variable | Hypertension |
| GFR | Initially preserved | ↓ (acute kidney injury) |
| Mechanism | Podocyte injury → protein leak | GBM inflammation → blood leak |
RPGN is a nephrology emergency. If creatinine is rising rapidly + active urine sediment (RBC casts, dysmorphic RBCs) - consult nephrology IMMEDIATELY for urgent biopsy. Untreated crescentic GN leads to irreversible ESRD within days to weeks. Do not wait for serologies to return before consulting.
Common Causes
| Nephrotic | Nephritic |
|---|---|
| Minimal change disease (children #1) | IgA nephropathy (#1 worldwide) |
| FSGS (adults #1, especially AA) | Post-streptococcal GN (children) |
| Membranous nephropathy (PLA2R antibody) | Lupus nephritis (class III/IV) |
| Diabetic nephropathy | ANCA vasculitis (GPA, MPA) |
| Amyloidosis | Anti-GBM (Goodpasture) |
Nephrotic Causes - Detailed
| Cause | Association | Biopsy Finding |
|---|---|---|
| Minimal Change Disease | Children (#1), NSAIDs, lymphoma (Hodgkin) | Normal on light microscopy; podocyte foot process effacement on EM |
| FSGS | HIV, obesity, heroin, African Americans | Focal and segmental sclerosis of glomeruli |
| Membranous Nephropathy | PLA2R antibody, cancer (lung, colon), hepatitis B | Subepithelial deposits ("spike and dome" on silver stain) |
| Diabetic Nephropathy | #1 secondary cause in adults, long-standing DM | Kimmelstiel-Wilson nodules, mesangial expansion |
| Amyloidosis | AL (myeloma) or AA (chronic inflammation) | Congo red stain → apple-green birefringence |
Nephritic Causes - Detailed
| Cause | Key Features | Biopsy / Diagnosis |
|---|---|---|
| IgA Nephropathy | Most common GN worldwide (Berger disease). Episodic gross hematuria with URI. | Mesangial IgA deposits on IF |
| Post-Streptococcal GN | Children 1–3 wk after pharyngitis. ASO titer ↑, low C3. | Subepithelial "humps" on EM, granular IF ("lumpy-bumpy") |
| Lupus Nephritis | Class III (focal) and IV (diffuse) are most severe. Low C3/C4, dsDNA+. | "Full house" IF (IgG, IgA, IgM, C3, C1q) |
| ANCA Vasculitis | GPA (c-ANCA/PR3) or MPA (p-ANCA/MPO). Pauci-immune GN. | Crescentic GN with few/no immune deposits (pauci-immune) |
| Anti-GBM / Goodpasture | Pulmonary hemorrhage + GN. Anti-GBM antibodies. | Linear IgG staining along GBM on IF |
| MPGN | Low C3 and C4. Hepatitis C association. | Mesangial and subendothelial deposits, "tram-tracking" of GBM |
🚨 Management
Nephrotic Syndrome Management
- ACEi/ARB -reduce proteinuria (first-line for ALL proteinuric kidney disease)
- Diuretics -loop diuretics for edema. May need albumin co-infusion if severe hypoalbuminemia.
- Statin -hyperlipidemia management
- Anticoagulation -consider if albumin < 2.5 (loss of antithrombin III → hypercoagulable state → renal vein thrombosis)
- Disease-specific treatment -steroids (MCD), rituximab (MN, FSGS), immunosuppression
Key Evidence: Rituximab is now first-line for primary membranous nephropathy MENTOR, 2019. For ANCA vasculitis, rituximab is noninferior to cyclophosphamide for induction RAVE, 2010 and superior for maintenance MAINRITSAN, 2014. For lupus nephritis class III/IV, add mycophenolate or cyclophosphamide to steroids ALMS, 2009. Voclosporin added to standard therapy improves renal response in lupus nephritis AURORA, 2021.
Nephritic Syndrome Management
- Treat underlying cause -immunosuppression for lupus nephritis, ANCA vasculitis
- BP control -ACEi/ARB preferred
- Supportive -fluid/salt restriction, diuretics if edema
- Urgent nephrology + renal biopsy -rapidly progressive GN (RPGN) is an emergency
Anticoagulation in nephrotic syndrome: Membranous nephropathy has the highest thrombotic risk. Consider prophylactic anticoagulation when albumin < 2.5 g/dL. Renal vein thrombosis presents as flank pain, hematuria, and sudden worsening of proteinuria. Diagnose with CT venography or Doppler ultrasound Lionaki, 2012.
🧪 Workup
- Urinalysis with microscopy -proteinuria, hematuria, RBC casts (nephritic), fatty casts/oval fat bodies (nephrotic)
- Spot urine protein/creatinine ratio (UPCR) -> 3.5 = nephrotic range
- 24-hour urine protein -gold standard quantification
- BMP -creatinine, eGFR
- Albumin, lipid panel
- Serologies: ANA, dsDNA, complement (C3/C4), ANCA, anti-GBM, PLA2R Ab, hepatitis panel, HIV
- Renal biopsy -usually needed for definitive diagnosis
Urine sediment clues: RBC casts = glomerulonephritis (nephritic). Fatty casts / oval fat bodies = nephrotic syndrome ("Maltese cross" under polarized light). Muddy brown casts = ATN. WBC casts = interstitial nephritis or pyelonephritis. Hyaline casts = normal or dehydration.
💊 Medications
| Drug | Dose | Purpose |
|---|---|---|
| Lisinopril (Zestril) | 5–40 mg daily | Reduce proteinuria. First-line for ALL proteinuric kidney disease. |
| Furosemide (Lasix) | 20–80 mg IV/PO | Edema management. May need high doses with hypoalbuminemia. |
| Prednisone (Deltasone) | 1 mg/kg daily × 4–8 wk | Minimal change disease (dramatic response). Taper over weeks. |
| Rituximab (Rituxan) | 375 mg/m² IV | Membranous nephropathy, refractory FSGS, lupus nephritis |
| Cyclophosphamide (Cytoxan) | Varies | ANCA vasculitis, severe lupus nephritis |
📋 On Rounds
Pimp Questions
Why are nephrotic patients hypercoagulable?
The kidney leaks antithrombin III (a key anticoagulant) in the urine along with other proteins. Loss of ATIII → uninhibited thrombin activity → hypercoagulable state. Clinical significance: renal vein thrombosis (especially in membranous nephropathy), DVT, PE. Consider prophylactic anticoagulation when albumin < 2.5 g/dL.
What is the most common cause of nephrotic syndrome in adults vs children?
Adults: FSGS (#1 overall, especially in African Americans) and membranous nephropathy (#1 primary cause in Caucasians). Diabetic nephropathy is the #1 secondary cause. Children: Minimal change disease (#1, ~80%). MCD responds dramatically to steroids -> 90% achieve remission within 4–8 weeks.
What is PLA2R antibody and why is it important?
Phospholipase A2 receptor antibody is positive in ~70% of primary membranous nephropathy. It distinguishes primary from secondary causes (cancer, lupus, hepatitis B). Titers correlate with disease activity and treatment response. MENTOR, 2019 showed rituximab is superior to cyclosporine for PLA2R+ MN.
What complement pattern helps distinguish nephritic causes?
Low C3 + C4: lupus nephritis, cryoglobulinemia (both activate classical pathway). Low C3 only (normal C4): post-streptococcal GN, C3 glomerulopathy, atypical HUS (alternative pathway). Normal complement: IgA nephropathy, ANCA vasculitis, anti-GBM disease (no complement consumption).
What is the significance of RBC casts on urinalysis?
RBC casts are pathognomonic for glomerulonephritis. They form when RBCs become trapped in Tamm-Horsfall protein casts within the tubules. Their presence confirms glomerular origin of hematuria (vs bladder, ureter, or kidney stone). Dysmorphic RBCs also suggest glomerular origin but are less specific.
When is renal biopsy indicated in nephrotic syndrome?
Adults: almost always indicated to guide treatment (except diabetic nephropathy with typical features - long-standing DM, retinopathy, no hematuria). Children: NOT needed for first episode with typical MCD presentation - empiric steroids. Biopsy if steroid-resistant, atypical features, or adult onset.
What is RPGN and why is it a nephrology emergency?
Rapidly Progressive Glomerulonephritis: loss of > 50% renal function over days to weeks. Characterized by crescents on biopsy (> 50% of glomeruli). Three categories: anti-GBM (type I), immune complex (type II: lupus, IgA, post-infectious), pauci-immune (type III: ANCA). Untreated leads to ESRD within weeks. Needs urgent biopsy and immunosuppression.
What is the MENTOR trial and what did it change?
MENTOR, 2019 (NEJM): Rituximab was noninferior to cyclosporine for inducing remission in membranous nephropathy at 12 months, and SUPERIOR at 24 months (60% vs 20% complete/partial remission). Rituximab is now first-line for primary MN. Less toxic than prior cyclophosphamide-based regimens.
Why do nephrotic patients develop hyperlipidemia?
Liver compensates for albumin loss by increasing protein synthesis, which includes increased lipoprotein (VLDL, LDL) production. Simultaneously, urinary loss of lipoprotein lipase cofactors reduces lipid clearance. Both mechanisms lead to marked hyperlipidemia. Treat with statins. Lipids normalize when nephrotic syndrome remits.
Clinical Examples
📋 Case 1 - Minimal Change Disease
Patient: 5-year-old boy presents with periorbital edema for 3 days. UA: 4+ protein, no blood. Labs: albumin 1.8 g/dL, cholesterol 380, Cr 0.4.
Diagnosis: Minimal change disease (most common nephrotic syndrome in children).
Key findings:
- Nephrotic range proteinuria (4+) with severe hypoalbuminemia (1.8)
- Periorbital edema - classic early sign in children (gravitational pooling while sleeping)
- No hematuria - confirms nephrotic (not nephritic) pattern
- Age 5 - MCD accounts for ~80% of nephrotic syndrome in children
Treatment: Prednisone 2 mg/kg/day (max 60 mg). Patient achieves complete remission within 4 weeks. No biopsy needed for first episode in children with typical presentation.
📋 Case 2 - ANCA Vasculitis (Nephritic)
Patient: 45M with gross hematuria, HTN (168/98), lower extremity edema. Labs: Cr 2.8 (baseline 1.0), UA with RBC casts. ANCA positive (p-ANCA/MPO).
Diagnosis: ANCA-associated rapidly progressive glomerulonephritis (RPGN).
Key findings:
- RBC casts - pathognomonic for glomerulonephritis (nephritic pattern)
- Rapidly rising creatinine (1.0 → 2.8) - RPGN is a nephrology emergency
- p-ANCA/MPO positive - microscopic polyangiitis (MPA)
- Renal biopsy: crescentic GN with pauci-immune pattern (few/no immune deposits)
Treatment: Pulse IV methylprednisolone 500–1000 mg x 3 days, then cyclophosphamide (or rituximab). Urgent nephrology consult - delay = irreversible renal loss.
📋 Case 3 - Membranous Nephropathy
Patient: 55F with progressive bilateral lower extremity edema, foamy urine. Labs: albumin 2.1, UPCR 8.2, Cr 1.1, cholesterol 340. PLA2R antibody positive.
Diagnosis: Primary membranous nephropathy.
Key findings:
- Nephrotic range proteinuria (UPCR 8.2) with hypoalbuminemia and hyperlipidemia
- PLA2R antibody positive - confirms primary membranous (~70% of cases)
- Age-appropriate cancer screening needed - membranous can be paraneoplastic (lung, colon, breast)
- High risk for renal vein thrombosis - membranous has the highest thrombotic risk of all nephrotic causes
Treatment: Started on rituximab (first-line immunosuppression for primary MN per MENTOR trial). ACEi for proteinuria reduction. Anticoagulation given albumin < 2.5. Monitor PLA2R titers for treatment response.
⚡ Summary
The Distinction Drives Everything
Nephrotic: proteinuria above 3.5 g/day, hypoalbuminemia, edema and hyperlipidemia, with a bland sediment. Nephritic: hematuria with dysmorphic red cells and red cell casts, hypertension, mild proteinuria and a falling GFR. Nephrotic is a podocyte problem; nephritic is inflammation of the glomerulus, and that difference decides both the differential and the urgency.
The Urine Sediment Is the Fastest Test You Have
Red cell casts = glomerulonephritis. Fatty casts and oval fat bodies with Maltese crosses under polarized light = nephrotic. Muddy brown casts = ATN. White cell casts = interstitial nephritis or pyelonephritis. Looking at the sediment yourself answers in minutes what serologies take days to confirm.
Nephrotic Causes by Population
Minimal change disease in children and with NSAIDs and lymphoma. FSGS, the commonest primary cause in adults, associated with HIV, obesity and heroin. Membranous nephropathy, associated with solid tumors, hepatitis B, lupus and anti-PLA2R antibodies. Diabetic nephropathy and amyloidosis as the systemic causes. Diabetes is the single commonest cause overall, so a long-standing diabetic with retinopathy and proteinuria often needs no biopsy.
Nephritic Causes by Complement and Serology
Low complement: post-infectious GN, lupus nephritis, membranoproliferative GN, cryoglobulinemia, endocarditis. Normal complement: IgA nephropathy, ANCA vasculitis, anti-GBM disease, Henoch-Schonlein purpura. Checking C3 and C4 early splits the differential in half before the biopsy result is back.
RPGN Is a Nephrology Emergency
A rapidly rising creatinine with an active sediment means call nephrology now for an urgent biopsy. Untreated crescentic glomerulonephritis causes irreversible end-stage renal disease within days to weeks, so the biopsy and empiric immunosuppression cannot wait for an outpatient appointment. Hemoptysis with nephritis means anti-GBM disease or ANCA vasculitis and needs plasma exchange considered alongside induction.
Baseline Nephrotic Management
Sodium restriction and loop diuretics for edema, often needing high or intravenous doses because diuretic bound to filtered albumin is less available. ACE inhibitor or ARB to reduce proteinuria, which is both a marker and a driver of progression. Statin for the hyperlipidemia. Treat the specific disease: steroids for minimal change, rituximab first line for primary membranous nephropathy (MENTOR).
Nephrotic Syndrome Is a Thrombotic State
Urinary loss of antithrombin III and other regulators makes these patients hypercoagulable. Membranous nephropathy carries the highest risk, and prophylactic anticoagulation is considered when albumin falls below 2.5 g/dL. Renal vein thrombosis presents as flank pain, hematuria and a sudden fall in renal function, and it is easy to attribute to the underlying disease instead.
Nephritic Management and the Immunosuppression Choice
Control blood pressure and volume, and treat the underlying cause. Post-infectious GN is supportive and usually self-limited. IgA nephropathy gets RAS blockade, with immunosuppression only for high-risk disease. ANCA vasculitis: rituximab is non-inferior to cyclophosphamide for induction (RAVE) and superior for maintenance (MAINRITSAN), and it avoids the infertility and bladder toxicity of cyclophosphamide. Also remember infection-related GN from endocarditis, where the treatment is antibiotics and source control, not immunosuppression.
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