Deep vein thrombosis, or DVT, is caused by a blood clot in a muscle and can be life-threatening. Symptoms include swelling, pain, and tenderness in the legs. Risk factors include immobility, hormone therapy, and pregnancy.

DVTs can occur anywhere in the body but are most frequently found in the deep veins of the legs, thighs, and pelvis. They may infrequently arise from the upper extremities usually because of trauma, or from an indwelling catheter (tubing) or device.

A deep vein thrombosis (DVT) is a condition wherein a blood clot (thrombus) forms in a vein of the deep system.

Thrombophlebitis is a condition in which there is both inflammation and a blood clot in a vein. Thrombophlebitis can occur in either superficial or deep veins. Superficial thrombophlebitis occurs in veins close to the skin surface, and usually causes pain, swelling, and redness in the area of the vein. Superficial thrombophlebitis usually is treated with heat, elevation of the affected leg or arm, and anti–inflammatory medications. A thrombosis in a deep vein is a much more serious problem than one in a superficial vein. The reason for this is that a piece of the clot in deep vein from a DVT can break off and travel through the deep veins back to the heart, and eventually be pumped by the heart into the arteries of the lung. When this happens, the condition is called pulmonary embolism (PE). The blood clot is called an embolus (plural emboli), and the process of breaking off and traveling to the lungs is called embolism.