Pulmonary Thromboembolism Quiz

Pulmonary Thromboembolism

• Macroscopic Infarcted Area:
  • Triangular shaped infarct, with the tip pointing towards the hilum
  • Occluded vessel is located at the tip of the infarct
  • Well defined, dark red color
• Macroscopic Chronic Pulmonary Congestion:
  • Lungs are increased in weight
  • They have a brown color due to the presence of siderophages
  • They have a firm consistency (brown induration)
• Microscopic Infarcted Area:
  • Well defined, red color due to erythrocyte flooding.
  • Preserved alveolar architecture with loss of nuclei, giving a "ghost-like appearance" or "Hiroshima effect" indicating necrosis.
• Microscopic Chronic Pulmonary Congestion:
  • Thick fibrotic interalveolar septa, due to:
    • Hypoxia
    • Reaction to deposited hemosiderin and cardiac cells/ heart failure cells/ siderophages
• Microscopic Hyperemic Narrow Rim:
  • Hypercellular area separating the infarcted tissue from the surrounding parenchyma
  • Composed of congested vessels, extravasated erythrocytes, and acute inflammatory infiltrate
  • Granulation tissue starts forming in this area with macrophages, fibroblasts, fibrocytes, and leukocytes.
• Microscopic Pulmonary Thromboembolism:
  • Thromboembolus present within a large branch of the pulmonary artery.

Pulmonary Infarction + Chronic Pulmonary Congestion

• Definition of Infarction:
  • Tissue death or necrosis due to insufficient arterial/oxygenated blood supply caused by sudden vascular occlusion, more frequent in arteries.
• Definition of Congestion:
  • A passive process caused by decreased venous outflow of blood from tissue.
  • Can be systemic, as in cardiac failure, or localized, as in isolated venous obstruction.
• Pathogenesis of Congestion:
  • Heart failure
  • Restricted respiratory movement
  • Compression of the cava vein
• Etiology of Chronic Pulmonary Congestion:
  • Chronic left ventricular failure
  • Mitral stenosis/incompetence

Clinical Features of Pulmonary Congestion and Infarction

• Pulmonary Congestion:
  • Dyspnea
  • Cough
  • Clubbing fingers (chronic hypoxia)
  • Auscultation reveals crackles (air bubbling and fluid)
• Pulmonary Infarction:
  • Pyramidal, wedge-shaped, or triangular shape (occluded vessel at the apex)
  • Early infarct: bulging area delimited by a hyperemic narrow rim
  • Old infarct: retracted scar tissue

Evolution and Complications of Pulmonary Congestion and Infarction

• Pulmonary Congestion:
  • Superinfection
  • Pulmonary fibrosis
  • Chronic cor pulmonale
• Pulmonary Infarction:
  • Organization/scarring
  • Encapsulation
  • Ulceration (cavity)
  • Superinfection (abscess)

Classification

• Pulmonary Congestion:
  • Acute pulmonary congestion:
    • Alveolar capillaries are engorged with blood
    • Serum extravasation due to increased intracapillary hydrostatic pressure and increased capillary permeability
    • Alveolar and septal edema
  • Chronic pulmonary congestion:
    • Pulmonary fibrosis and sclerosis (thickening of septa)
    • Intraalveolar and septal hemosiderin-laden macrophages
    • Brown induration of the lungs
• Pulmonary Infarction:
  • White/anemic infarct: in solid/compact tissues such as Myocardium (heart attack), Spleen, Kidney, Brain (liquefactive necrosis), Liver (hepatic artery), Limb (gangrene)
  • Red (hemorrhagic) infarct: in spongy tissues with dual or collateral circulation, such as Lungs and Intestine
  • Zahn infarction: a pseudo-infarction in the liver caused by portal vein obstruction; the area of congestion atrophies but no necrosis occurs.

Lymphatic Edema

• Causes:
  • Filaria parasites
  • Surgical removal of the lymph nodes
  • Congenital
  • Milroy disease
• Elephantiasis: a severe consequence of Lymphatic edema, characterized by extreme swelling of the limbs, particularly the legs.

Morphology of Edema

• Macroscopic changes appear when the quantity of intercellular fluid increases with 10%:
  • Tissues become swollen and pasty
  • Finger-shaped depressions appear
  • Gelatinous aspect on section
• Tissues can appear in different colors depending on the cause:
  • Blue: venous and cardiogenic edema
  • Pale: hypoalbuminemic edema
  • Red: inflammatory edema

Macroscopic Description of Pulmonary Edema

• Lungs:
  • Distended
  • Hyperemic
  • Increased volume and weight
  • Do not collapse on the autopsy table
  • Pink-gray color, darker in dorsal and basal areas
  • Pasty in consistency (wet sponge)
• Pleura:
  • Distended
  • Thin
  • Transparent
  • Smooth and shiny
  • Rib imprints on the pleural surface
• Compression of the cut surface:
  • Elimination of a pink-red foamy, frothy fluid containing edema fluid, a few erythrocytes, and air bubbles.

Microscopic Description of Pulmonary Edema

• Lung parenchyma:
  • Alveolar spaces filled with homogeneous or slightly granular eosinophilic material (edema fluid).
  • Two types of edema:
    • Septal edema: edema fluid inside alveolar septa
    • Alveolar edema: edema fluid mixed with air bubbles and rare cellular elements like desquamated alveolocytes, alveolar macrophages, and leukocytes.
• Congested Vessels:
  • Excessive accumulation of blood
  • Dilated capillaries
• Anthracotic pigment:
  • Black color pigment resulting from inhalation of carbon particles, ingested by alveolar/interstitial macrophages and accumulated in connective tissue and/or regional lymph nodes.