Common Hemorrhagic Conditions
Hemorrhage refers to the escape of red blood cells from the circulating blood out of the cardiac chamber or vascular lumen into the tissue spaces, body cavities, or body surface. Hemorrhage is both physiological and pathological: physiological hemorrhage, such as menstruation in women; and pathological hemorrhage, such as bleeding caused by trauma, vascular lesions, and hemorrhagic diseases.
According to the site of occurrence, hemorrhage is divided into two major categories: internal hemorrhage and external hemorrhage. Internal hemorrhage is the escape of blood into a body cavity or tissue; external hemorrhage is the escape of blood out of the body.
Internal hemorrhage can occur anywhere in the human body. Some internal hemorrhages can be observed on the body surface as petechiae or ecchymoses. A small amount of bleeding under the skin, mucosa, or serosa forming small punctate hemorrhages locally is called a petechia; a slightly larger hemorrhage (3–5 mm in diameter) is called purpura; a subcutaneous hemorrhage more than 1–2 cm in diameter is called an ecchymosis.
Blood accumulating in a body cavity is called a hematocele, such as a pericardial hematocele or a joint hematocele; a localized large hemorrhage within a tissue is called a hematoma, such as a subdural hematoma or a subcutaneous hematoma.
External hemorrhage is more common; the most frequent is bleeding from the body surface caused by trauma. Some special forms of external bleeding have specific names: bleeding from the nasal mucosa is called epistaxis; respiratory-tract blood expelled through the mouth is called hemoptysis; gastrointestinal blood expelled through the mouth is called hematemesis; gastrointestinal blood expelled through the anus is called hematochezia; and urinary-tract bleeding is called hematuria.
According to its mechanism, hemorrhage is divided into two types: rhexis hemorrhage and diapedesis hemorrhage.
Rhexis hemorrhage is caused by the rupture of the heart or a blood-vessel wall; it can occur at any site of the cardiovascular system and is generally a large-volume hemorrhage. Common causes include the following:
1. Mechanical trauma—the most common cause of bleeding, such as crush injuries, cuts, puncture wounds, gunshot wounds, or cardiac rupture. 2. Disease of the heart or vessel wall itself, such as a ventricular aneurysm after myocardial infarction, aortic aneurysm, atherosclerosis, or arteriovenous developmental malformations, which can cause rupture bleeding. 3. Erosion of the vessel wall by surrounding lesions, most commonly the erosion of vessel walls by malignant tumors, inflammatory damage to vessel walls, and the destruction of vessel walls by gastroduodenal ulcers. 4. Venous rupture, commonly seen in the rupture of esophageal varices in late-stage liver cirrhosis. 5. Capillary rupture, most often seen in soft-tissue injuries.
Diapedesis hemorrhage refers to bleeding in which capillary permeability increases and blood leaks out of the vessels; it is generally a small-volume hemorrhage. Common causes include:
1. Vessel-wall damage: seen in hypoxia, toxins, allergies, and vitamin C deficiency. 2. Thrombocytopenia and platelet dysfunction, commonly seen in aplastic anemia, idiopathic thrombocytopenic purpura, and congenital platelet dysfunction. 3. Coagulation-factor deficiency, such as the deficiency of two coagulation factors in hemophiliacs, the reduction of three liver-related coagulation factors in liver disease, as well as the excessive consumption of coagulation factors during diffuse systemic bleeding.
The human body has a hemostatic function: slow, small-volume bleeding can usually stop on its own. A small amount of blood in local tissue or a body cavity can be cleared by absorption; a larger hematoma that is incompletely absorbed may undergo organization or fibrous encapsulation. The effect of hemorrhage on the body depends on the type, volume, speed, and site of the bleeding.
When blood loss exceeds 20%–25% of the body's circulating blood volume in a short time, hemorrhagic shock can occur. Bleeding in vital organs—such as cardiac rupture or cerebral hemorrhage—can cause serious consequences even when the volume is small; for example, cardiac rupture causes intrapericardial hematocele, which, due to cardiac tamponade, can lead to acute heart failure. Long-term small-volume bleeding can cause anemia.
Bleeding is only an external phenomenon, and the factors that induce it are various, so treatment cannot be generalized. The cause of traumatic bleeding is very clear, but some hemorrhagic conditions are signals that the body has developed a major disease; for example, purpura may be related to thrombocytopenia, hematemesis to gastric cancer, hemoptysis to lung cancer, painless hematuria to bladder cancer, and epistaxis to nasopharyngeal carcinoma.
(This article was compiled based on the relevant content of the 10th edition of Pathology, People's Medical Publishing House.)