Nephritic Syndrome Notes

Nephritic Syndrome Overview

  • Definition: Nephritic syndrome is characterized by glomerular inflammation and bleeding.

Clinical Features

  • Proteinuria: Limited to less than 3.5 g/day, distinguishing it from nephrotic syndrome.
  • Oliguria: Decrease in urine production.
  • Azotemia: Increased nitrogenous waste products in the blood.
  • Salt and Fluid Retention:
    • Leads to edema, particularly periorbital edema due to loose connective tissue around the eyes.
    • Results in hypertension.
  • Hematuria: Glomerular bleeding results in red blood cell casts in the urine, indicative of glomerular bleeding.

Pathophysiology

  • Glomerular Bleeding: Blood enters the tubules, forming casts shaped like the tubules.
  • Glomerular Biopsy Findings:
    • Hypercellular inflamed glomerulus due to immune complex deposition driving inflammation.
    • C5a from complement activation attracts neutrophils, causing damage.

Prototypic Disorders

  • Post-Streptococcal Glomerulonephritis (PSGN):
    • Occurs after infection with nephrogenic strains of group A beta-hemolytic streptococcus (GABHS), usually skin or pharynx infections.
    • Presentation:
    • Classic occurrence 2-3 weeks post-infection with symptoms of hematuria (cola-colored urine), oliguria, hypertension, and periorbital edema.
    • Predominantly seen in children but can occur in adults.
    • Biopsy Characteristics:
    • Hypercellular glomerulus on biopsy, granular immunofluorescence pattern.
    • Subepithelial humps on electron microscopy due to immune complex deposits.
    • Management: Supportive treatment is usually sufficient; the deposits resolve over time.

Rapidly Progressive Glomerulonephritis (RPGN)

  • Definition: Nephritic syndrome that progresses to renal failure within weeks to months.
  • Biopsy Findings:
    • Presence of crescents in Bowman's space, made up of fibrin and macrophages.
  • Immunofluorescence Analysis helps determine etiology:
    1. Linear Immunofluorescence: Indicative of Goodpasture syndrome, characterized by antibodies against the glomerular basement membrane (GBM) leading to simultaneous lung and kidney involvement.
    2. Granular Immunofluorescence: Typical for PSGN and diffuse proliferative glomerulonephritis (most common renal disease observed in systemic lupus erythematosus).
    3. Pauci-Immune: Negative immunofluorescence, usually requiring ANCA (anti-neutrophil cytoplasmic antibody) testing.

ANCA Testing

  • C-ANCA (cytoplasmic): Associated with Wegener's granulomatosis, involves lung, kidney, and nasopharynx.
  • P-ANCA (perinuclear): Associated with microscopic polyangiitis or Churg-Strauss syndrome (which presents with eosinophilia, asthma, and granulomatous inflammation).

IgA Nephropathy

  • Definition: Most common cause of nephropathy worldwide; characterized by IgA immune complex deposition in the mesangial region.
  • Presentation: Episodic gross/microscopic hematuria following mucosal infections due to excess IgA production.

Alport Syndrome

  • Definition: Inherited defect in type IV collagen, leading to thinning and splitting of the glomerular basement membrane.
  • Key Findings:
    • Isolated hematuria, sensory hearing loss, and ocular disturbances with a family history of similar symptoms.

Conclusion

  • Management: Focus on supportive treatment; maintain awareness of disease complications such as rapidly progressive glomerulonephritis and potential progression to renal failure, especially in adults with nephritic syndrome.