Hemorrhage

A hemorrhage occurs due to a rupture of the blood vessel wall or increased permeability. Blood vessels rupture from various causes including trauma, atherosclerosis, high blood pressure, or tumor-induced vascular wall erosion. Capillary bleeding often results from blood stasis in capillaries or minor injuries and manifests as a consequence of many clinical disorders known as hemorrhagic diathesis. Bleeding can be external or internal. Internal hemorrhage involves blood leaking into tissue or organs, forming hematomas that can range from small to very large, such as in life-threatening brain bleeds.

Hematomas also include internal hemorrhages. Small 1-2 mm hematomas on the skin, mucous membranes, or serous membranes appear as petechiae. Petechiae result from increased permeability of blood vessel walls, decreased platelet count, or altered platelet function. Multiple petechiae are termed purpura, which can result from the same causes as petechiae, as well as from bruises, vasculitis, or vascular fragility.

When blood vessels rupture, blood may accumulate in body cavities. The clinical outcome of hemorrhages depends on the volume of lost blood and the speed of bleeding. Rapid loss of a significant amount of blood can lead to hemorrhagic (hypovolemic) shock. Additionally, the clinical course of hemorrhages varies depending on the bleeding site. For example, bleeding from minor soft tissue trauma is generally not dangerous, whereas bleeding of the same intensity from a ruptured brain arteriole can result in death due to complications.