Acute Inflammation

• dilation of small blood vessels

• accumulation of leukocytes and fluid in the extravascular tissue

Classification according to the morphologic appearance:

• Non-suppurative Inflammation

  • Catarrhal inflammation

  • Serous inflammation

  • Fibrinous inflammation

  • Hemorrhagic inflammation

  • Membranous/pseudo-membranous inflammation

  • Necrotizing (gangrenous) inflammation

  • Allergic inflammation

• Suppurative Inflammation

  • Localized:

    • Abscess inflammation

    • Furuncle

    • Carbuncle

  • Diffuse:

    • Cellulitis

Acute Non-suppurative Inflammation

• without pus formation

Catarrhal inflammation

• excess mucus secretion due to inflammation of mucus membranes

Site: mucous membranes

Example: common cold (rhinovirus), influenza

Gross appearance: congestion, edema, mucus secretion

==Microscopic examination: ==

• blood vessel dilation, congested (filled with blood)

• excess mucus on epithelial surface

• few or absence of neutrophils

Serous Inflammation

• watery protein-poor fluid (effusion)

• typically does not contain microbes or large numbers of leukocytes

• Derived from:

  • serum

  • mesothelial cell secretion

Site: spaces created by cell injury or into body cavities lined by the peritoneum, pleura, or pericardium.

Examples: skin blister (burn), pleural effusion (pleurisy)

Gross appearance: congested surface, watery effusion

Fibrinous Inflammation

• fibrinous exudate

Site: lining of body cavities, (meninges, pericardium, and pleura)

Example: serosal surfaces (fibrinous pericarditis)

Hemorrhagic Inflammation

• exudate rich in red blood cells

Example: severe capillary damage (anthrax, plague)

Membranous/Pseudo-membranous Inflammation

• necrotic membrane on mucus surfaces

Example: diphtheritic pharyngitis, bacillary dysentery

Gross appearance: greyish membrane on mucosal surface

==Microscopic examination: ==

• necrotic mucosa

• fibrin and inflammatory cells adherent to mucosal surface

Necrotizing (Gangrenous) Inflammation

Example: gangrenous acute appendicitis, gangrene of the foot

Allergic Inflammation

Example: bronchial asthma

==Microscopic examination: ==

• exudate rich in eosinophils

• extensive edema

Acute Suppurative (Purulent) Inflammation

• purulent exudate (pus): fluid, necrotic cells, and pus cells (dead neutrophils)

Localized

• abscess formation

Organisms: pyogenic bacteria (Staphylococcus aureus)

Diffuse

Cellulitis: diffuse suppurative inflammation

Site: subcutaneous tissue (orbit, pelvis, scrotum, mediastinum)

Organisms: Streptococcus hemolyticus

Chronic Inflammation

• Chronic “non-specific” or diffuse inflammation

• Chronic specific inflammation

Diffuse Non-specific Inflammation

• diffuse chronic inflammatory cell infiltrate

Example: chronic pyelonephritis, chronic cholecystitis

Chronic Specific Inflammation (Granuloma)

• caseating granulomatous inflammation

  • Example: Tuberculosis

• non-caseating granulomatous inflammation

  • Example: leprosy, syphilis, schistosomiasis, sarcoidosis and foreign body granuloma