(See also Overview of Blood Clotting Disorders.)
Disseminated intravascular coagulation (DIC) begins with excessive clotting. The excessive clotting is usually stimulated by a substance that enters the blood as part of a disease (such as an infection or certain cancers) or as a complication of childbirth, retention of a dead fetus, or surgery. People who have a severe head injury or who have tissue damage caused by shock, burns, frostbite, other injuries, or even a bite by a poisonous snake are also at risk. As the clotting factors and platelets (cell fragments that circulate in the bloodstream and help blood clot) are depleted, excessive bleeding occurs.
DIC may develop
Slowly developing disseminated intravascular coagulation typically results from cancer, aneurysms, or cavernous hemangiomas (collections of dilated blood vessels).
DIC that develops suddenly usually causes bleeding, which may be very severe. If the condition follows surgery or childbirth, bleeding may be uncontrollable. Bleeding may occur at the site of an intravenous injection or in the brain, digestive tract, skin, muscles, or cavities of the body.
If DIC develops more slowly, as in people with cancer, then clots in veins (deep venous thrombosis) are more common than bleeding. If clots form in veins (usually in the legs), the person may have swelling, redness, or pain in the area. However, sometimes no symptoms develop. A clot that forms in a vein may break free and travel (becoming an embolus) to the lungs. Clots in the lungs may make people short of breath.
Blood tests may show that the number of platelets in a blood sample has dropped (platelets are used up when blood clots) and that the blood is taking a long time to clot. The diagnosis of DIC is confirmed if test results show abnormally increased quantities of plasma D-dimer (a substance that blood clots release when they break down; more D-dimer indicates that more clots are being produced than usual) and often a low or decreasing level of fibrinogen (a protein that is consumed when blood clots).
The underlying disorder must be identified and corrected, whether it is an obstetric problem, an infection, or a cancer. The clotting problems subside when the cause is corrected.
DIC that develops suddenly is life threatening and is treated as an emergency. Platelets and clotting factors are transfused to replace those depleted and to stop bleeding. Heparin may be used to slow the clotting in people who have more chronic, milder DIC in which clotting is more of a problem than bleeding.