- Q1 Position of a deep vein thrombosis (DVT)
A deep vein thrombosis (DVT) can form in any deep vein. The signs and symptoms caused by it are largely related to the level at which it forms.
Below the knee, the deep veins are very small in diameter. There are three pairs of very small veins that run with the arteries in the muscles of the lower leg. The veins are only a couple of millimetres in diameter and if a deep vein thrombosis (DVT) forms in one of them, there are five others to take over the role of the vein.
At the knee, all of these veins have combined into one vein called the popliteal vein. If the deep vein thrombosis (DVT) forms at this level, it will affect blood flow out of the whole of the lower leg.
Between knee and hip (an "above knee deep vein thrombosis"), progressively more of the leg is the higher than the point at which the deep vein thrombosis (DVT) forms.
If the deep vein thrombosis (DVT) occurs in the groin or in the pelvic veins (iliac veins), then this affects the venous outflow from the whole of the leg.
Therefore, simply, the lower down the leg the deep vein thrombosis (DVT) forms, the less of the leg can be affected and the milder the symptoms. As we will see later, also the lower the risks.
As the level of the deep vein thrombosis (DVT) goes up the leg and into the pelvis, the more severe the symptoms and signs. Again as we will see later, the higher the level of the deep vein thrombosis (DVT), the higher the risks.
- Q2 Size of a deep vein thrombosis (DVT)
A deep vein thrombosis (DVT) causes most of its local effects in the legs by:
Causing the local vein to become inflamed and tender
Blocking the flow of blood in the vein that it is within
By stopping blood flowing into that vein by blocking junctions with other tributaries
If the deep vein thrombosis is short, then it is unlikely to be blocking the drainage of any of the tributaries draining blood into the deep system and so the symptoms and signs will be will be less. The greater the length of the deep vein thrombosis, the more likely that it will block the drainage of tributaries into the deep vein and so cause worsening symptoms and signs due to impeded drainage of blood from tributaries.
- Q3 Whether a deep vein thrombosis (DVT) is occlusive
A deep vein thrombosis (DVT) is attached to the wall of the deep vein. It may only be attached at one point and may be non-occlusive, meaning that blood can still flow past it. This will not cause any symptoms to the blood being "dammed" up behind it.
On the other hand, it may be occlusive, completely stopping blood flow in the vein which in turn can allow the stationary blood to clot and form further thrombosis - called "extension of the deep vein thrombosis (DVT)". In addition, swelling of the leg below this is more likely, as the blood is being "dammed" up behind the blockage.
- Q4 What are the signs and symptoms of a new (acute) deep vein thrombosis (DVT)?
When a blood clot or 'thrombosis' forms in the veins, the body tries to break it down straight away. The bodys method of repair is a process called inflammation. During inflammation, specialist cells - called white blood cells - are brought into the area, so that they can attack anything that is going wrong, whether it be an infection, dead tissue or as in this case, a blood clot. As the white blood cells remove whatever the target is, the body slowly "heals" and returns to as close to normality as possible.
The process of inflammation has four main parts - redness, heat, pain and swelling (or for those who like the classic Latin description 'rubor', 'calor', 'dolor' and 'tumor'). All of these are caused by the increased blood supply to the area which is needed to get the white cells and nutrients locally for the healing process.
The redness is due to increase blood flow, as is the increased heat. The pain is a by-product of the substances produced by the local tissue that signal injury and start the inflammatory process (substances such as bradykinin). Finally, swelling is the product of increased blood supply. With increased blood flow locally, fluid that leaks out of the capillaries into the affected area. This swelling is increased further by the huge number of white blood cells within the fluid, working to cause healing.
Therefore once a clot or thrombus forms on the vein wall, the vein wall starts secreting substances such as bradykinin, starting the process of inflammation in the local area. This causes localised discomfort or pain, and very localised swelling. As the vein is deep within the muscle, this swelling is probably not noticeable at this stage. However movement of the muscle irritates the inflammation, causing pain and tenderness of the affected muscle.
If the clot or thrombus is occlusive and/or blocks enough tributaries that drain into this deep vein, then the limb will swell to a greater or lesser extent below the level of the clot. If the thrombus is in the lower leg veins below the knee, there may be a little ankle swelling but rarely more. An occlusive large deep vein thrombosis (DVT) at the level of the knee can cause considerable discomfort and swelling of the leg below the knee. It can also cause some discolouration as venous blood cannot get out of the leg, making the affected leg look a little more "blue" and tense.
If the deep vein thrombosis (DVT) is in the thigh or even up into the pelvis, and is occlusive, then progressively more of the leg will be swollen, tender and may be discoloured.
- Q5 Phlegmasia caerula dolens - Painful blue swollen leg
The most extreme sort of deep vein thrombosis (DVT) of the leg is a condition known as "phlegmasia caerula dolens
". This literally means the swollen blue painful leg due to an abnormality of the veins. It rarely happens with a simple deep vein thrombosis and is usually only found in patients with other severe illnesses, often cancer or some other severe problem.
In phlegmasia caerula dolens
, the leg usually swells very quickly, turns blue and parts of the skin may start to turn very deep blue or even black as the blood cannot get away from the skin. The skin becomes very tense, uncomfortable and even painful. Ultrasound
shows that the deep veins are usually completely blocked with the thrombus extending down tributaries preventing much venous flow at all from leg.
- Q6 What are the signs and symptoms of an old (chronic) deep vein thrombosis (DVT) - also called "postphlebitic limb"?
It used to be thought that when a patient has a deep vein thrombosis (DVT), the inflammation that is caused in the healing process destroys the valves in the deep veins and scars the walls. It was thought that this always lead to a condition called "postphlebitic limb".
However research from Prof CV Ruckley in Edinburgh (Scotland) at the end of the 1990s showed this not be the case. His research showed that if a deep vein thrombosis (DVT) is diagnosed quickly and treated completely, the deep veins and their valves are usually spared and the patient goes back to a completely normally functioning the venous system. It appears from his research that people who get postphlebitic limb, are those who:
Have recurrent deep vein thrombosis' (DVT) and therefore recurrent episodes of inflammation
Or, who have had missed deep vein thrombosis (DVT) and so had no treatment allowing inflammation to continue
Or, who have had inadequate treatment allowing the deep vein thrombosis (DVT) to continue causing inflammation
The obvious common factor in the development of a postphlebitic limb is that the deep vein thrombosis is not removed quickly, and so the deep veins remained inflamed for longer than they need to. It is this chronic or long-term inflammation that seems to destroy the deep valves and damage the deep vein walls.
The term "postphlebitic limb" is often used for a leg that has had severe venous disease for a long time, resulting in the skin in the lower leg being discoloured and brown, particularly around the inner aspect of the ankle, swelling of the lower leg particularly around the ankle and usually marked discolouration patches of the leg with large venous flares particularly over the foot.
Interestingly, many patients who appear with legs looking like this actually have severe varicose veins
or superficial venous reflux ("hidden varicose veins"), and the external look of the leg mimics a postphlebitic limb. The advent of duplex ultrasound
has shown us that in the past (and unfortunately even today), many patients are told that they have a "postphlebitic limb" and are incurable whereas if they were seen by a venous specialist and had a high resolution duplex ultrasound scan
performed by an experienced operator, would find that they merely had varicose veins
or "hidden varicose veins" that can be easily treated and cured.
Hence the diagnosis of postphlebitic limb should never be made without an in-depth venous duplex ultrasound
scan performed by an expert.
- Q7 Pulmonary embolism (PE) - a complication of deep vein thrombosis (DVT)
The descriptions of deep vein thrombosis (DVT) above relate to the local effects of a deep vein thrombosis (DVT) in the leg, both acutely and chronically.
However the most worrying of the complications of the deep vein thrombosis (DVT) is the formation of a pulmonary embolism (PE).
A pulmonary embolism is a blood clot (thrombus) that has moved up through the veins of the pelvis and abdomen, through the right heart and into the lungs.
Small pulmonary emboli can fly up through the venous system, through the heart and impact into the lungs causing variable symptoms and signs. However small ones rarely cause severe ill-health or death.
Sudden death from a pulmonary embolism is usually caused by a large clot embolising through the right hand side of the heart and into the lungs. It used to be thought that the clot hitting the lungs was the thing that caused death in these patients. However it now appears that the cause of death is due to a long clot getting caught up in the right hand side of the heart, stopping it pumping efficiently and making the blood "froth". This means that the right hand side of the heart fails as a pump (acute right heart failure) which can lead to death very quickly.
Therefore the signs and symptoms of pulmonary embolism (PE) depend on the size of the clot that is embolised.
Very small pulmonary emboli (PE) might be completely "silent" and might not cause any signs or symptoms at all. They might be found by accident during a medical examination or might be found when enough of them have occurred and caused many blockages throughout the lungs, so that the patient finds difficulties with breathing.
Small pulmonary emboli (PE) often present as sudden episodes of chest pain that are worse on breathing in (a sign called "pleuritic chest pain"). When a doctor listens with a stethoscope to the chest, a strange "rubbing" sound can be heard as the rough and area of inflamed lung rubs against the chest wall (a sign called a "pleural rub").
Large pulmonary emboli (PE) present with sudden chest pain and sudden shortness of breath and are a medical emergency.
Very large pulmonary emboli (PE) can cause sudden death. One of the strange associations with sudden death from pulmonary emboli (PE) is the desire to open one's bowels. Very often patients who have died acutely from massive pulmonary emboli (PE) are found dead on the toilet.
It is not known whether the straining on the toilet causes a deep vein thrombosis (DVT) in the pelvic veins to suddenly embolise to the lungs or whether the action of a massive clot embolising to the right hand side of the heart and lungs causes an outpouring of inflammatory chemicals that has the effect of making the patient feel that they need to urgently open their bowels.