4. Hemorrhagic infarct of the lung

Last updated on January 17, 2019 at 16:49

Staining: HE

Organ: Lung

Description:

In the middle of the slide you can see an artery that is blocked by a red-colored embolus. We can see a kinda cake-piece-shaped area from the embolus to the bottom corner that is more eosinophilic than the rest of the slide. Zooming in on the eosinophilic part shows lack of nuclei, presence of RBCs, eosinophilia and loss of cell structure. Along the lower right side of the triangle there is a very dark red part, made red by RBCs.

On the top part of the slide we can see normal lung tissue. The area between the normal lung tissue and the necrotic part has neutrophils inside the alveoli.

Diagnosis: Haemorrhagic infarct of the lung

Theory:

Causes for haemorrhagic infarct:

  • Embolization
  • Local vasoconstriction around the embolus due to paracrine factors
  • Venous backflow due to heart failure
  • Loose lung parenchyme

The embolus is red in this cause because it originates from a vein. The lung tissue around the necrosis is atelectatic, meaning that the alveoli are collapsed so they contain very little volume. This is because of infarct pneumonia, the inflammation caused by bacteria that grow around and in the infarct. If this is not treated and the patient survives, there will be gangrene formation.

The outcome of pulmonary embolization differs based on which pulmonary vessel is blocked. If the pulmonary trunk is blocked, there is total embolization which always causes death. If a pulmonary artery is blocked there is subtotal embolization, and the consequence is almost always death. The most normal case however, which is not usually associated with death, is the partial or segmental embolization, where a segmental branch of the pulmonary artery is blocked. A fourth type is called microembolization, caused by a disease called DIC (disseminated intravascular coagulopathy).

Left-sided heart failure is a risk factor for lung infarction, as it causes congestion of the pulmonary circulation. When a branch of the pulmonary artery is then blocked by an embolus will the venous blood flow back into the lung, causing the haemorrhage.

See also theoretical topic 4.

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