There are two main groups of veins in the legs: the superficial veins and the deep veins. When blood clots form in the deep veins, this is known as a Deep Vein Thrombosis or Deep Venous Thrombosis (DVT). These terms mean the same. The deep veins cannot be seen externally. The superficial veins can be seen through the skin and sometimes form varicose veins when they become enlarged. Superficial veins can sometimes develop blood clots. This is called phlebitis or superficial thrombophlebitis. Thrombosis can actually take place in any of the veins throughout the body, but is most frequent in the legs.
DVT in the legs can be divided into 3 main types classified by their location. Firstly ilio-femoral DVT affects the major vein in the pelvis (iliac vein) draining the leg and may also involve the femoral vein in the thigh. Femoro-popliteal vein DVT predominantly affects the femoral vein in the thigh and the popliteal vein behind the knee. Calf vein (tibial vein) DVT predominantly affects the smaller deep veins in the lower leg. These divisions are largely arbitrary and DVT may affect all of these veins or segments of a vein that don't readily fit into this classification. The divisions are useful in terms of assessing the severity and risk of complications. Ilio-femoral DVTs are likely to present with the most severe symptoms and the highest risk of subsequent complications and calf vein DVTs with the lowest risk of complications.
The main symptoms of a DVT are pain and swelling in the affected leg, particularly in the calf. The calf may be slightly red and tender. These symptoms can vary widely in their severity and are also not very specific. It can be difficult to make the diagnosis of DVT on the symptoms alone, because many other unrelated disorders can also cause similar symptoms.
Occasionally DVT can be very severe and affect the deep and superficial veins. In these circumstances the venous drainage from the limb may be so impaired that venous gangrene can develop. There is often an underlying cause for this event, such as an underlying cancer or clotting disorder. It can be a very difficult situation to treat.
Usually a combination of factors lead to the development of a DVT. Some of these factors can be described as external factors. For instance a combination of immobility and cramped seats, with the front of the seat pressing on the calf, may be important in the economy class syndrome. Aircraft cabin pressure may also play a role. There do seem to be factors related particularly to air travel which cause activation of the coagulation system (Schreijer AJM et al, 2006). A UK government report (Sunday Times, September 2nd, 2001) has investigated factors which could influence the development of DVT during air travel. It has indicated that decreased cabin pressure and altered sleep patterns because of jet lag may be important in the development of DVT. They have suggested that more studies to investigate the links between air travel and DVT should be funded.
Immobility is also important in patients undergoing surgery. The combination of a long surgical operation and a prolonged period of bedrest will increase the risk of DVT. A recent study has also highlighted the increased risk of DVT for up to 12 weeks after surgery, even minor surgery, in middle-aged women (Million Women Study, 2009).
Apart from these external factors there may also be internal factors which increase the likelihood of an individual person developing a DVT. Important risk factors include age over 40 years, pregnancy, presence of cancer, hormone therapy (hormone replacement therapy, the oral contraceptive pill) and dehydration.
The diagnosis of DVT may be suspected by the symptoms and signs in an individual patient and the circumstances of the patient. For instance, pain and swelling in one calf, in a patient after major surgery or a long flight, will raise a suspicion of DVT, which will require exclusion with further tests. The same symptoms that develop following a game of squash are more likely to be due to a muscle injury. Clinical diagnosis alone is unreliable and inaccurate and further tests are required.
The main test used to exclude or diagnose DVT is Duplex ultrasound scanning. This is a simple, painless test with a high degree of accuracy. Ultrasound can demonstrate clot within the deep veins. It is particularly accurate in the larger veins of the leg. The image on the left is an ultrasound scan showing thrombus (the blood clot) with some blood flowing around the clot.
In the calf veins ultrasound is more difficult, but can be accurate in experienced hands. Unfortunately ultrasound can be time consuming and costly. As the majority of tests will be normal, clinicians are trying to find ways to reduce the number of normal scans performed. One way to do this is to measure D-dimer levels on a blood test.
Fortunately, a DVT can be treated and the risk of immediate serious complications can be reduced. The main treatment is anticoagulation and compression stockings.
Anticoagulation is a treatment that thins the blood making it less likely to clot. This is usually started using an injection (heparin) which is continued for between 5 and 10 days. This is because heparin acts very rapidly helping reduce the risk of further problems as soon as it is started. When heparin is started after a clot has formed, it is started at a higher (therapeutic) dose. Most patients today receive low molecular weight heparin (LMWH) as it can be given as a once or twice daily dose and is as effective as the older unfractionated heparins which require daily monitoring with blood tests.
While still having heparin, a further treatment with warfarin is started. Warfarin also thins the blood, but it can be taken in a tablet form. These tablets act more slowly and it often takes 4 or 5 days before the blood is thinned sufficiently so that the heparin can be stopped. Warfarin is continued for between 3-6 months and requires regular monitoring of blood clotting tests to make sure it is working properly. If you have had more than one DVT it may be important to remain on warfarin for the rest of your life. Warfarin is very inconvenient to take because of the regular monitoring that is required. There are newer drugs becoming available and undergoing trials which may replace warfarin over the next 5-10 years.
In general provided the blood supply to the tissues is good and compression is applied, when appropriate, it hardly matters which dressing is placed onto the ulcer bed. As long as it is clean, dry and non-adherent the ulcer should respond. Many claims are made for different types of dressings, most of which are hard to substantiate. Regular changes of dressing type usually have little value and may actually do harm as patients often develop reactions (dermatitis) to dressings and exudate. A review and meta-analysis of dressings for venous ulcers showed that the type of dressing applied beneath compression was not shown to influence healing (Palfreyman S, Nelson EA, Michaels JA, 2007).
It is perfectly acceptable to clean your leg and ulcer with ordinary tapwater. There is no benefit in using sterile water or saline. If you have a planned visit from the district nurse then, by arrangement, it can be useful to shower and clean the leg, if your are able, prior to the planned visit. Only do this after discussion.
