Blood clotting is a natural process in which blood cells and strands of fibrin clump together to stop bleeding after a blood vessel has been injured. Eventually, the clot forms a protective scab over a healing wound. If the body didn’t have the ability to clot blood, people would bleed to death after a minor cut.

Sometimes blood clots form even when a person hasn’t been injured. Most tend to dissolve on their own without any problem, but sometimes blood clots can cause medical problems. Blood clots become dangerous when they block blood flow through an artery or a vein. When a blood clot stops blood flow to an artery in the heart or brain, a heart attack or stroke can result. Blood clots also can block veins in other parts of the body, causing conditions like varicose veins or pulmonary embolism (a life-threatening blood clot in the lungs).

When a blood clot forms and stays where it forms, it’s called a thrombus. A thrombus that breaks loose or travels from where it formed and goes to another location in the body is called an embolus. Sometimes a piece of plaque, small pieces of tumor, fat globules, air or amniotic fluid can act like an embolus – breaking loose and traveling somewhere to block off blood flow.

Physicians treat blood clots with a variety of methods. These include medications such as anticoagulants (drugs to help prevent blood clots) or clot busters (drugs that help dissolve blood clots that have formed). In more serious situations, surgeons may opt for a catheter-based procedure or surgery to remove the clot.

Deep vein thrombosis (DVT) affects mainly the veins in the lower leg and thigh; it involves the formation of a clot (thrombus) in the larger veins of this area. The thrombus may interfere with circulation in this area, and it may break off and travel through the bloodstream (embolize). The embolus could lodge in the brain, lungs, heart or other area, causing severe damage to that organ.

Risk factors for DVT include prolonged sitting, bed rest, immobilization (such as on a long plane or car trip), recent surgery or trauma (especially hip, knee or gynecological injury or surgery), fractures, childbirth within the last six months and the use of medications containing estrogen, such as the birth control pill. Other disease processes also increase the risk of blood clot; these include malignant tumors, polycythemia vera, and inherited or acquired blood-clotting disorders. DVT is seen more commonly in adults over the age of 60 but can occur in any age group.

Symptoms may include leg pain in one leg only, tenderness in one leg only, swelling of one leg only, or increased warmth or changes in skin color of one leg only. The doctor usually will order a Doppler ultrasound exam of the leg to try to visualize the vessels and see the clot.

Once DVT is diagnosed, treatment is designed to stop the development of an embolus (movement of the clot) and to prevent DVT from happening again.

For years, the treatment goal of anticoagulation was achieved through IV infusion and a medication called warfarin. This required hospitalization. Some clots now are treated with a new type of heparin, administered through an injection once or twice a day to shorten the hospital stay or eliminate the need for hospitalization. Patients typically must remain on warfarin for several months and have their blood-clotting factors monitored weekly.

Most DVTs disappear with treatment, but there is a risk of recurrence. Some patients may develop chronic pain and swelling in the leg known as post-phlebitic syndrome. Pulmonary embolus is uncommon when DVTs are treated properly.

To make an appointment with a Washington University vascular surgeon, please call (314) 747-VASC (8272).

Washington University physicians are the medical staff of
Barnes-Jewish Hospital and St. Louis Children's Hospital