Lungs Circulatory - Pathology

Embolism, thrombosis and infarction

Pulmonary infarction (Image sourced from Bristol Biomed Image Archive with permission)

Segmental pulmonary infarction (Image sourced from Bristol Biomed Image Archive with permission)

Lungs are strategically situated to catch emboli carried in venous blood
Because the lung is supplied by both pulmonary and bronchial arteries and has extensive collateral channels, infarction usually does not follow embolism or thrombosis unless pulmonary circulation is already compromised
In animals, greatest risk comes from:
- Tumor emboli
  - From e.g.: osteosarcoma and haemangiosarcoma in dogs, uterine carcinoma in cattle
- Septic emboli
  - From bacterial endocarditis, jugular thrombophlebitis, hepatic abscesses etc.
  - May cause unexpected death if in large numbers
  - May develop suppurative pneumonia -> pulmonary abscesses, arteritis, thrombosis
Pulmonary infarcts usually occur when there is embolisation or thrombosis during general circulatory collapse or passive congestion of heart failure
Pulmonary thromboembolism is a sequel to in cattle to large emboli from liver abscesses close to the vena cava
- Death may ocur due to massive haemorrhaging into lung tissue
Parasites (e.g. Dirofilaria immitis, Angiostrongylus vasorum) may be responsible
Long-term intravenous catheterisation may cuse thrombi pieces breaking off and lodging in pulmonary vessels

Caused by left-to-right vascular shunts or increased resistance of the pulmonary vascular system

In animals, it is most commonly a sequel of widespread fibrosis in the lung or chronic bronchitis or bronchiolitis which stimulates hypertrophy in the walls of small arteries
Severe prolonged pulmonary hypertension leads to cor pulmonale, right-sided heart failure secondary to primary lung disease