Nephrotic versus Nephritic Syndrome

Introduction

• Focus on nephrotic vs nephritic syndrome in the kidneys
• Understanding requires exploring pathophysiology

Kidney Structure Overview

• Cross-section of kidney capillaries shows:
  • Endothelium: Surrounds the vascular lumen with slits
  • Basement Membrane: Permeable to multiple substances
  • Epithelial Cells (Podocytes): Create a tight sieve to prevent large substances (like proteins) from passing
• Fluid leaves the vasculature and enters Bowman's space, eventually leading to urine production

Nephrotic Syndrome

• Definition: Loss of nephron function leads to protein loss due to podocyte dysfunction (e.g., loss, receding, or involution).
• Key Characteristics:
  • Loss of approximately 3.5 grams of protein per day.
  • Symptoms:
    • Frothy urine: Caused by protein in urine.
    • Edema: Due to fluid leakage; often observed in periorbital area, legs, and lungs.
    • Decreased Albumin: Major protein responsible for retaining fluid in vessels.
    • Increased Lipids in Blood: Liver compensates for losing protein by increasing lipids.
    • Antithrombin III Loss: Leading to a hypercoagulable state, increasing risk of thrombosis and embolisms (e.g., DVT, pulmonary embolism).
• Causes:
  • Primary Nephrotic Diseases: Affect kidney inherently.
  • Secondary Causes: Non-kidney diseases that induce nephrotic syndrome.

Nephritic Syndrome

• Definition: Caused by immune complexes reacting with glomeruli, leading to inflammation.
• Key Characteristics:
  • Immune depression leads to recruitment of white blood cells and capillary damage.
  • Symptoms:
    • Hematuria: Presence of blood in urine.
    • Oliguria: Low urine output due to glomerular damage, leading to lower GFR.
    • Hypertension: Due to reduced kidney filtering capacity.
    • Granular casts in urine: Indicative of inflammation in the glomerulus.
• Distinction from Nephrotic Syndrome: Nephritic syndrome has more cell debris and inflammatory cells.

Summary

• Nephrotic Syndrome:

  • High protein in urine; frothy urine; edema; decreased albumin & antithrombin III; increased lipids.
  • Considered when >3.5 grams of protein lost daily, minimal active sediment.

• Nephritic Syndrome:

  • Hematuria; low urine output; high blood pressure; inflammatory debris in urine.
  • Characterized by immune response in glomeruli, with increased inflammation.

• Further Lectures: Upcoming discussions will cover primary and secondary diseases affecting both syndromes.