Hemorrhagic infarction and its organ manifestation

1. Definition

• Hemorrhagic (red) infarct (出血性梗塞) = ischemic necrosis in which blood floods the necrotic tissue (contrast: pale/anemic white infarct).
• A drainage problem; can be either coagulative (most solid organs) or liquefactive (brain).

2. When Does a Red Infarct Occur?

• Venous occlusion (e.g. testicular/ovarian torsion)
• Loose tissues (lung) that readily reabsorb blood
• Dual circulation (lung — pulmonary + bronchial; intestine — SMA + IMA)
• Reperfusion of a previously occluded/necrotic area (leaky vessels rupture)

Coagulative hemorrhagic	Liquefactive hemorrhagic
AMI after reperfusion	Cerebral infarct (encephalomalacia rubra)
Pulmonary infarct
Intestinal infarct

3. Organ Manifestations

Acute myocardial infarction (after reperfusion)

• Usually hemorrhagic because we reperfuse; necrotic vessels are leaky → rupture → haemorrhage (see A/08).

Pulmonary infarct (dual circulation)

• Cause: embolism from deep vein thrombosis (90% femoral/iliac/popliteal).
  • Large/saddle embolus → sudden death (no time for morphology).
  • Medium/small → endothelial damage → haemorrhage.
• Infarct only when bronchial circulation is compromised (CHF): lower lobes, wedge-shaped (apex → hilum), red-blue → red-brown (hemosiderin) → white scar.
• ~60–80% silent; large emboli → ↑pulmonary pressure, ↓cardiac output, right heart failure, hypoxemia, possible R→L shunt through foramen ovale.

Intestinal infarct (dual SMA/IMA)

• SMA thrombus → necrosis of duodenum/jejunum → massive blood loss, peritonitis, septic shock.
• IMA thrombus → usually compensated by SMA.
• Portal vein thrombus → haemorrhagic necrosis of the whole intestine.
• Subtypes: mucosal (often reversible) → mural (multifocal, submucosal edema) → transmural (all layers; gangrene + perforation after 24 h; ~90% mortality).

Cerebral infarct — encephalomalacia rubra (haemorrhagic)

• Red colour from haemorrhage due to: reperfusion, venous thrombosis, or border-zone (watershed) necrosis (e.g. circle of Willis — anastomotic, ischemia-prone).

💡 High-yield: Red infarcts occur in organs with dual blood supply / loose tissue (lung, intestine), after venous occlusion, or after reperfusion. The lung is the classic site of a wedge-shaped haemorrhagic infarct.