Nephritic syndrome

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Nephritic Essentials - Inflamed & Leaky Filters

  • Pathophysiology: Glomerular inflammation (proliferative changes) damages the capillary wall, creating pores that allow RBCs and some protein to leak into the urine.
  • Clinical Hallmarks:
    • Hypertension (salt/water retention)
    • Oliguria (↓ GFR)
    • Hematuria (cola-colored urine)
    • Edema (periorbital)
  • Urinalysis: The key diagnostic finding is RBC casts. Also shows dysmorphic RBCs and hematuria. Proteinuria is present but sub-nephrotic (< 3.5 g/day).

Nephrotic vs. Nephritic Syndrome Glomerular Damage

Post-streptococcal glomerulonephritis (PSGN) is the classic example, typically developing 1-3 weeks after a streptococcal pharyngitis or impetigo. Look for low C3 levels.

Etiology - A Cast of Characters

  • Post-Infectious Glomerulonephritis (PIGN)

    • Most common: Post-streptococcal (PSGN), typically 1-3 weeks after pharyngitis or impetigo.
    • Others: Endocarditis, shunt nephritis, abscesses.
  • IgA Nephropathy (Berger's Disease)

    • Most common primary glomerulonephritis worldwide.
    • Often follows URI/GI infection (synpharyngitic).
  • Rapidly Progressive Glomerulonephritis (RPGN) - Crescentic

    • Type I (Anti-GBM): Goodpasture's syndrome.
    • Type II (Immune Complex): Complication of PIGN, IgA, Lupus Nephritis, MPGN.
    • Type III (Pauci-Immune): ANCA-associated vasculitis (GPA, MPA).
  • Hereditary Nephritis

    • Alport Syndrome: Defect in Type IV collagen.

Immunofluorescence patterns in nephritic syndrome

Exam Favorite: PSGN classically shows a "lumpy-bumpy" granular pattern on immunofluorescence due to subepithelial immune complex deposits.

Workup & Dx - The Clinical Detective

  • Urinalysis (UA) First:
    • Hematuria (>3 RBCs/hpf)
    • RBC casts & dysmorphic RBCs are hallmark findings.
    • Sub-nephrotic proteinuria (<3.5 g/day)
  • Bloodwork:
    • ↑ BUN & Creatinine (azotemia)
    • ↓ Complement levels (C3, C4) suggest post-strep, lupus, or MPGN.
    • Serology: ASO (post-strep), anti-dsDNA (SLE), ANCA (vasculitis).
  • Kidney Biopsy: Gold standard for definitive diagnosis & guiding therapy.

Red blood cell casts in urine sediment

RBC casts are pathognomonic for glomerular hematuria, essentially confirming glomerulonephritis as the cause of bleeding.

Management - Damage Control

  • Goal: Control hypertension, edema, and hypervolemia to prevent immediate complications (e.g., hypertensive encephalopathy, pulmonary edema).
  • Core Interventions:
    • Salt & Water Restriction: Foundational first step.
    • Loop Diuretics: Furosemide is first-line for managing volume overload and hypertension.
    • Vasodilators: Add if blood pressure remains uncontrolled (e.g., CCBs, hydralazine).
  • Severe/Refractory Cases:
    • Dialysis for unresponsive fluid overload, severe hyperkalemia, or uremic symptoms.

⭐ In rapidly progressive glomerulonephritis (RPGN), treatment is urgent: initiate high-dose pulse corticosteroids (e.g., methylprednisolone) ± cyclophosphamide or rituximab.

Sites of action of diuretics in the nephron

High-Yield Points - ⚡ Biggest Takeaways

  • Nephritic syndrome is an inflammatory process causing hematuria (RBC casts), oliguria, azotemia, and hypertension.
  • Post-streptococcal glomerulonephritis (PSGN) is the classic prototype, typically affecting children 1-3 weeks after a GAS infection.
  • Key labs show low C3 levels and elevated anti-streptolysin O (ASO) or anti-DNase B titers.
  • Biopsy in PSGN reveals "lumpy-bumpy" granular immunofluorescence and characteristic subepithelial humps on electron microscopy.
  • Management is primarily supportive.

Practice Questions: Nephritic syndrome

Test your understanding with these related questions

A 41-year-old man presents at an office for a regular health check-up. He has no complaints. He has no history of significant illnesses. He currently takes omeprazole for gastroesophageal reflux disease. He occasionally smokes cigarettes and drinks alcohol. The family history is unremarkable. The vital signs include: blood pressure 133/67 mm Hg, pulse 67/min, respiratory rate 15/min, and temperature 36.7°C (98.0°F). The physical examination was within normal limits. A complete blood count reveals normal values. A urinalysis was ordered which shows the following: pH 6.7 Color light yellow RBC none WBC none Protein absent Cast hyaline casts Glucose absent Crystal none Ketone absent Nitrite absent Which of the following is the likely etiology for hyaline casts in this patient?

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Flashcards: Nephritic syndrome

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One clinical feature of renal failure is _____, which is a symptomatic clinical syndrome marked by increased nitrogenous waste products in the blood (azotemia)

TAP TO REVEAL ANSWER

One clinical feature of renal failure is _____, which is a symptomatic clinical syndrome marked by increased nitrogenous waste products in the blood (azotemia)

uremia

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