Causes

Traumatic
Traumatic bleeding is caused by some type of injury. There are different types of wounds which may cause traumatic bleeding. These include:


 * Abrasion - Also called a graze, this is caused by transverse action of a foreign object against the skin, and usually does not penetrate below the epidermis
 * Excoriation - In common with Abrasion, this is caused by mechanical destruction of the skin, although it usually has an underlying medical cause
 * Hematoma - (also called a blood tumor) - caused by damage to a blood vessel that in turn causes blood to collect under the skin.
 * Laceration - Irregular wound caused by blunt impact to soft tissue overlying hard tissue or tearing such as in childbirth. In some instances, this can also be used to describe an incision.
 * Incision - A cut into a body tissue or organ, such as by a scalpel, made during surgery.
 * Puncture Wound - Caused by an object penetrated the skin and underlying layers, such as a nail, needle or knife
 * Contusion - Also known as a bruise, this is a blunt trauma damaging tissue under the surface of the skin
 * Crushing Injuries - caused by a great or extreme amount of force applied over a long period of time. The extent of a crushing injury may not immediately present itself.
 * Gunshot wounds - Caused by a projectile weapon, this may include two external wounds (entry and exit) and a contiguous wound between the two

The pattern of injury, evaluation and treatment will vary with the mechanism of the injury. Blunt trauma causes injury via a shock effect; delivering energy over an area. Wounds are often not straight and unbroken skin may hide significant injury. Penetrating trauma follows the course of the injurious device. As the energy is applied in a more focused fashion, it requires less energy to cause significant injury. Any body organ, including bone and brain, can be injured and bleed. Bleeding may not be readily apparent; internal organs such as the liver, kidney and spleen may bleed into the abdominal cavity. The only apparent signs may come with blood loss. Bleeding from a bodily orifice, such as the rectum, nose, ears may signal internal bleeding, but cannot be relied upon. Bleeding from a medical procedure also falls into this category.

Due to underlying medical conditions
Medical bleeding is that associated with an increased risk of bleeding due to an underlying medical condition. It will increase the risk of bleeding related to underlying anatomic deformities, such as weaknesses in blood vessels (aneurysm or dissection), arteriovenous malformation, ulcerations. Similarly, other conditions that disrupt the integrity of the body such as tissue death, cancer, or infection may lead to bleeding.

The underlying scientific basis for blood clotting and hemostasis is discussed in detail in the articles, Coagulation, haemostasis and related articles. The discussion here is limited to the common practical aspects of blood clot formation which manifest as bleeding.

Certain medical conditions can also make patients susceptible to bleeding. These are conditions that affect the normal "hemostatic" functions of the body. Hemostasis involves several components. The main components of the hemostatic system include platelets and the coagulation system.

Platelets are small blood components that form a plug in the blood vessel wall that stops bleeding. Platelets also produce a variety of substances that stimulate the production of a blood clot. One of the most common causes of increased bleeding risk is exposure to non-steroidal anti-inflammatory drugs (or "NSAIDs"). The prototype for these drugs is aspirin, which inhibits the production of thromboxane. NSAIDs inhibit the activation of platelets, and thereby increase the risk of bleeding. The effect of aspirin is irreversible; therefore, the inhibitory effect of aspirin is present until the platelets have been replaced (about ten days). Other NSAIDs, such as "ibuprofen" (Motrin) and related drugs, are reversible and therefore, the effect on platelets is not as long-lived.

There are several named coagulation factors that interact in a complex way to form blood clots, as discussed in the article on coagulation. Deficiencies of coagulation factors are associated with clinical bleeding. For instance, deficiency of Factor VIII causes classic Hemophilia A while deficiencies of Factor IX cause "Christmas disease"(hemophilia B). Antibodies to Factor VIII can also inactivate the Factor VII and precipitate bleeding that is very difficult to control. This is a rare condition that is most likely to occur in older patients and in those with autoimmune diseases. von Willebrand disease is another common bleeding disorder. It is caused by a deficiency of or abnormal function of the "von Willebrand" factor, which is involved in platelet activation. Deficiencies in other factors, such as factor XIII or factor VII are occasionally seen, but may not be associated with severe bleeding and are not as commonly diagnosed.

In addition to NSAID-related bleeding, another common cause of bleeding is that related to the medication, warfarin ("Coumadin" and others). This medication needs to be closely monitored as the bleeding risk can be markedly increased by interactions with other medications. Warfarin acts by inhibiting the production of Vitamin K in the gut. Vitamin K is required for the production of the clotting factors, II, VII, IX, and X in the liver. One of the most common causes of warfarin-related bleeding is taking antibiotics. The gut bacteria make vitamin K and are killed by antibiotics. This decreases vitamin K levels and therefore the production of these clotting factors.

Deficiencies of platelet function may require platelet transfusion while deficiciencies of clotting factors may require transfusion of either fresh frozen plasma of specific clotting factors, such as Factor VIII for patients with hemophilia.