Deep venous thrombosis is a blood clot that forms in a vein deep inside a part of the body. It mainly affects the large veins in the lower leg and thigh.

DVTs are most common in adults over age 60; however, they can occur at any age.

When a clot breaks off and moves through the bloodstream, this is called an embolism. An embolism can get stuck in the brain, lungs, heart or other area, leading to severe damage.

Risk factors include:

  • A pacemaker catheter that has been passed through the vein in the groin
  • Bed rest or sitting in one position for too long such as plane travel
  • Family history of blood clots
  • Fractures in the pelvis or legs
  • Giving birth within the last 6 months
  • Pregnancy
  • Obesity
  • Recent surgery (most commonly hip, knee or female pelvic surgery)
  • Too many blood cells being made by the bone marrow, causing the blood to be thicker than normal

DVT mainly affects the large veins in the lower leg and thigh, almost always on one side of the body.

To treat the blood clots, your doctor will give you medicine to thin your blood. This will keep more clots from forming or old ones from getting bigger. In rare cases, you may need surgery if medicines do not work.

Many DVTs disappear without a problem, but they can return. Some people may have long-term pain and swelling in the leg called postphlebitic syndrome.

You may also have pain and changes in skin color. These symptoms can appear right away or you may not develop them for 1 or more years afterward. Wearing tight (compression) stockings during and after the DVT may help prevent this problem.

Blood clots in the thigh are more likely to break off and travel to the lungs than blood clots in the lower leg or other parts of the body.