Deep vein thrombosis (also known as deep venous thrombosis and usually abbreviated as DVT) is the formation of a blood clot ("thrombus") in a deep vein. It is a form of thrombophlebitis. Deep vein thrombosis commonly affects the leg veins or the deep veins of the pelvis. Occasionally the veins of the arm are affected (if spontaneous, this is known as Paget-Schrötter disease). A DVT can occur without symptoms, but in many cases the affected extremity will be painful, swollen, red, and warm, and the superficial veins may be engorged. The most serious complication of a DVT is that the clot could dislodge and travel to the lungs, which is called a pulmonary embolism (PE)...