Legs have two sets of veins—superficial veins and the deep veins that drain blood from the leg muscles. A deep vein thrombosis (DVT) is a blood clot that forms in the veins deep in the leg, usually in the calf or thigh, although DVT can occur in other veins including the pelvis and rarely in the arms [1, 2]. DVT can partially or completely block blood flow through a vein but not everyone with DVT will experience symptoms .
Doctors refer to DVT as distal or proximal; distal DVT refers to DVT of the calf, proximal DVT refers to DVT above the knee and above a major vein called the popliteal vein . Most DVT form in the calf area and many do not cause any symptoms. Proximal DVT is more serious than distal DVT. One in two people with untreated proximal DVT will develop symptomatic PE within 3 months .
In many cases of DVT, the clots are small and do not cause any symptoms . Most patients have symptoms when there is proximal vein involvement and these symptoms can include :
Always talk to your doctor if you have any concerns about DVT or if you think you have symptoms of DVT.
Each year, about one in 1200 people in Australia and New Zealand are affected by VTE [4,7]. DVT became well known several years ago because of its association with flying for long periods (often called ‘traveller’s thrombosis’ or ‘economy class syndrome’), but the risk of getting a DVT is higher in hospitalised patients. Only about one in 6000 people who go on a long flight (more than 4 hours) will develop DVT , but if you are in hospital particularly for a major operation or because of a serious illness, your risk of having a blood clot in your leg or lungs is much higher than usual . Hospitalised patients are over 100 times more likely to develop a DVT or PE compared with the rest of the community .
A DVT may not cause further problems, but complications of DVT can occur. These include: