Venous thrombosis is a blood clot that develops in the veins. The two most common types of venous thrombosis are deep vein thrombosis (DVT) and pulmonary embolism (PE).

Deep Vein Thrombosis
Pulmonary Embolism

Deep Vein Thrombosis

Deep vein thrombosis, or DVT, is a blood clot in the veins of the body. The deep veins pass through the center of the leg and are surrounded by muscles. DVTs usually occur in the legs, particularly in the groin, calves, or behind the knee. DVTs can damage valves in the leg veins and can result in pain, swelling, discoloration, and/or leg sores. The primary risk of a DVT is that it will develop into a pulmonary embolism. If left untreated, approximately 25 percent of DVTs escalate into a life-threatening pulmonary embolism.

Pulmonary Embolism

Pulmonary emolism, or PE, is a blood clot that breaks loose and travels to the lungs. A PE can occur if fragments of a DVT (or the entire clot itself) loosen from the vein of the leg and travel (or "embolize") to the lungs, where they lodge in one or more of the major veins that carry blood from the lungs to the heart. A pulmonary embolism can be life-threatening, depending on the size of the blood clot and how quickly it is treated.

If a person has had a DVT, they are at higher risk for having another DVT in the future. Many research studies have studied why some people have another venous thrombosis and why others do not.

The latest research suggests that men are three times more likely than women (20 percent versus 6 percent) to have an additional blood clot. It remains unclear exactly what triggers a recurrence, but additional risk factors (such as genes and lifestyle) certainly play a role.