The veins of the body are divided into two major categories: superficial and deep. The superficial veins are located close to the skin and are sometimes visible through the skin. The deep venous system is located deep within the muscles. Deep vein thrombosis (DVT) is a blood clot that forms in one of these veins, most often in the legs. A clot in a superficial vein rarely causes serious complications, but a DVT is dangerous because the clot can travel to the heart, which then pumps it into the lungs and causes a pulmonary embolism. A pulmonary embolism is the blockage of a blood vessel in a lung, and it kills at least 100,000 Americans every year.
About 10 percent of people who have DVT also develop a pulmonary embolism, so it is important to spot the signs of DVT early and to seek treatment before the clot has a chance to move. DVT is characterized by pain and tenderness in the affected area, which progressively worsens. The skin overlying the clot may also take on a blue or red hue and feel warm to the touch. Treatment with blood thinners and compression stockings is often sufficient to prevent the DVT from moving while the body naturally dissolves the clot. However, more serious cases may require the use of a clot-busting medication or surgery to remove the clot.