Glomerulonephritis

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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). Glomerulus structure and filtration barrier

⭐ 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.

Microscopic view of urine casts

  • 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_._

Practice Questions: Glomerulonephritis

Test your understanding with these related questions

An 8-year-old child presents with hematuria 5 days after a throat infection. What is the most likely diagnosis?

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Flashcards: Glomerulonephritis

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Steroid-resistant nephrotic syndrome is defined as failure to achieve remission after _____ weeks of corticosteroid therapy.

TAP TO REVEAL ANSWER

Steroid-resistant nephrotic syndrome is defined as failure to achieve remission after _____ weeks of corticosteroid therapy.

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