Glomerulonephritis

GN Basics - Filter Failure Fiesta

• Glomerulonephritis (GN): Inflammation of glomeruli, kidney's primary filtration units.
• Core Pathology: "Filter Failure Fiesta" - breakdown of glomerular filtration barrier.
  • Barrier components: Endothelium, Glomerular Basement Membrane (GBM), Podocytes (visceral epithelial cells).
  • Damage → ↑permeability → leakage of RBCs & proteins.
• Key Manifestations:
  • Hematuria (RBCs in urine): Often "cola-colored" or smoky urine.
  • Proteinuria (protein, esp. albumin, in urine): Leads to frothy urine, edema.
• Classification (Simplified):
  • Mechanism: Immune-mediated (most common), Pauci-immune, Anti-GBM disease, Non-immune.
  • Origin: Primary (kidney-limited) vs. Secondary (systemic disease association).

⭐ Glomerular damage in most GNs is primarily immune-mediated, involving antibodies, complement activation, and cellular immune responses.

Clinical Clues - Spotting the Swell

• Key presentation: Acute Nephritic Syndrome.
• Edema:
  • Periorbital edema (classic, esp. morning), often pitting.
  • Progresses to dependent edema (pedal, sacral), ascites, anasarca.
• Hematuria:
  • Microscopic (RBCs, significant RBC casts in urine sediment).
  • Macroscopic: Characteristic 'Coca-Cola' or 'smoky' colored urine.
• Hypertension: Acute onset; may be severe (e.g., hypertensive encephalopathy).
• Oliguria: ↓ urine output (typically < 1 mL/kg/hr in children).
• Proteinuria: Present, usually sub-nephrotic range.
• Systemic symptoms: Malaise, fever, flank or abdominal pain.

⭐ The classic triad of nephritic syndrome is hematuria, hypertension, and edema; 'Coca-Cola' or 'smoky' urine is a hallmark of gross hematuria.

Diagnostic Drill-Down - Unmasking the Culprit

• Urinalysis: Key initial test!
  • Hematuria, Proteinuria
  • RBC casts: Pathognomonic.

  ⭐ Presence of RBC casts in urine sediment is pathognomonic for glomerulonephritis, indicating glomerular bleeding.

• Blood Tests:
  • KFT: ↑ Urea, ↑ Creatinine, ↓ eGFR.
  • Serum electrolytes.
  • Complements: ↓ C3 (PSGN, MPGN), ↓ C4 (Lupus Nephritis).
  • Serology: ASLO (post-strep), ANA (lupus), ANCA (vasculitis).
• Imaging:
  • USG KUB: Kidney size, echogenicity; rule out other causes.
• Renal Biopsy: Gold standard for diagnosis & therapy guidance.
  • Indications: Atypical, RPGN, steroid-resistant nephrotic syndrome, unclear Dx.

Major GN Types - Rogues' Gallery

• Post-Streptococcal GN (PSGN)
  • 📌 "Post-Strep GN: 1-3 wks post-pharyngitis, 3-6 wks post-impetigo; Low C3; ASO positive."
  • Acute nephritic syndrome (edema, HTN, hematuria).
  • Labs: ↓C3, ↑ASO/Anti-DNase B. Biopsy (if atypical): Subepithelial "humps".
  • Prognosis: Excellent in children.
• IgA Nephropathy (Berger's Disease)
  • Most common primary GN. Episodic gross hematuria (often synpharyngitic).
  • Labs: Normal C3, Serum IgA often ↑. Biopsy: Mesangial IgA deposits.
  • Prognosis: Variable; 20-30% progress to ESRD in 20 yrs.
• Henoch-Schönlein Purpura (HSP) Nephritis / IgA Vasculitis
  • Systemic: palpable purpura, arthritis, abdominal pain, renal disease.
  • Renal: Mesangial IgA (histologically similar to IgA nephropathy). Labs: Normal C3.
  • Prognosis: Generally good; monitor renal function & BP.
• Rapidly Progressive GN (RPGN) / Crescentic GN
  • Clinical emergency: Rapid ↓ GFR (days-weeks). Severe oliguria.
  • Biopsy: Extensive crescent formation (>50% of glomeruli).
  • Prognosis: Poor without urgent, aggressive immunosuppression.

⭐ Post-streptococcal glomerulonephritis (PSGN) is the most common cause of acute nephritic syndrome in children worldwide and typically has an excellent prognosis with supportive care.

High‑Yield Points - ⚡ Biggest Takeaways

• PSGN: Cola-colored urine, edema, HTN 1-2 weeks post-strep; low C3, ↑ASO.
• IgA Nephropathy (Berger's): Most common primary GN; recurrent gross hematuria with URTI. Normal C3.
• HSP Nephritis: Systemic vasculitis; palpable purpura, arthritis, abdominal pain, renal (IgA) involvement.
• RPGN: Crescents on biopsy, rapid renal function decline; requires urgent management.
• Alport Syndrome: X-linked; hematuria, sensorineural deafness, ocular defects (e.g., lenticonus).
• RBC casts in urine indicate glomerular bleeding; biopsy for definitive diagnosis_._