Deep vein thrombosis: What is it, why does it occur and what are its complications?

Deep vein thrombosis: What is it, why does it occur and what are its complications?
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Deep vein thrombosis is a relatively common disease, the difficulties of which can be mild and insignificant. However, the other side of the problem is the risk of developing pulmonary embolism and thromboembolic disease.


Deep vein, or also venous, thrombosis is a relatively common disease that affects the venous system. These are most often the veins of the lower limbs.

This disease can occur mildly with mild difficulties. However, the other and serious side is the risk of developing embolism in the lungs and, in the long term, also thromboembolic disease.

Even minor difficulties need to be investigated and not underestimated. Early diagnosis and appropriate treatment will avert acute or late complications. These can significantly reduce the quality of life.

Pulmonary embolism is one of the most serious complications
that threatens the health and life of a affected person. 

What are blood vessels, veins, and thrombosis?

To begin with, a brief introduction that will improve orientation in the issue.

From a simple and practical point of view, the vessels are divided into arteries and veins.

It is generally known that:

  1. the arteries are filled with oxygenated blood, ie blood rich in oxygen
  2. the veins are filled with OD-oxygenated blood, ie blood with a low oxygen content and a higher carbon dioxide content

However, this general awareness is not entirely accurate.

It is more accurate as follows ...

1. The arteries  - arteries are the vessels that carry blood from the heart.
A good and prime example is the lungs.
The pulmonary artery recedes from the right atrium.
It conducts OD oxygenated blood from the heart to the lungs.

Only in the lungs does the blood re-oxygenate. And this oxygenated blood leads back to the left heart ...

2. Veins  - veins are the vessels that carry blood to the heart.
We ended up with the lungs ... so:
Oxygenated blood goes to the heart, more precisely to the left atrium, with  4 pulmonary veins.

Lung = pulmonary trunk - truncus pulmonalis,
further divided into pulmonary arteries and other smaller vessels. 
Pulmonary veins = 4 veins leading to the heart - venae pulmonales. 

And from the other relatively large majority, the rule is that the blood in the arteries is saturated with oxygen. The one in the veins contains a higher ratio of carbon dioxide.

Greek arteries:
Aer = air, 
terrein = contain.


Blood vessels are part of the cardiovascular and lymphatic systems.

Important nutrients and oxygen are distributed through the blood. Plus, waste products are also transported in the blood, and these are formed during metabolism and need to be removed from the body.

Arteries and veins also differ in their structure. The vein wall contains fewer muscle cells, and the veins themselves differ from each other, depending on their location.

An example is the veins of the lower limbs, which also contain valves.
The valves in these veins prevent blood from flowing back against gravity.
Their damage and insufficient function lead to the accumulation of blood in the lower limbs.

In addition to the valves, arteries are involved in the flow of blood from the lower limbs. 

How is that?

The vessels of the lower limbs, ie arteries + veins, are in a common and tight fit. Rhythmic contraction of the muscles of the arteries of the lower limbs helps blood flow in the veins. Plus, the flow is directed by the flaps.


When the blood from the lower limbs returns, the muscles of the lower limbs are also important. The muscles act as a muscle pump. When moving, walking the surrounding muscles compress the blood vessels. This improves the return of blood from the lower limbs to the body against the force of gravity.

Therefore, lack of exercise and long-term sitting or standing is not appropriate. Still, movement is better.

Good to know ...

There is high pressure in the arteries, so when they are damaged, the blood sprays from them.

On the contrary, the pressure in the veins is low, when the blood vessel wall is damaged, blood flows out of them.

In some veins, the pressure is even lower than atmospheric.
This is important when the blood returns to the heart.
Blood is literally sucked in by the heart. 

If certain veins are damaged, there is a risk of air suction and thus an air embolism.

The veins are also divided into so-called superficial and deep.

The surfaces are richly branched and interconnected. Plus, the connection to the deep vein system recedes from them. 

The deep veins are located mostly together with the arteries. And so they are located deeper.

Plus, a system of connecting cores that connects the cores on the surface with those in-depth

In short, and in general, the relationship between surface and deep veins can be described as,
imagine streams and small rivers flowing into large rivers ...

The superficial veins collect blood from the structures of the lower limb, which in turn flows into large deep veins. This is the vein of the popliteal,  ie the femoral vein, and the femoral vein, ie the femoral vein.

Read also: Thrombosis is not a disease of the elderly. It also endangers young people .

Thrombosis is ...

Thrombosis = blood clotting. It can take place in the blood vessels and in the heart.

Blood clotting is important mainly for: 
preventing blood loss,
which protects against bleeding 
from damaged blood vessels.

However, this blood clotting is not always justified and desirable. An example is the condition of thrombosis. He can have various causes.

In general, there is a mismatch between the balance between hemocoagulation and fibrinolysis

Hemocoagulation is a process of blood clotting
that aims to stop bleeding - hemostasis.
Fibrinolysis is the process of dissolving a blood clot. 

These are complex mechanisms when their mutual balance is disturbed, the following arises:
1 . state of excessive clotting, ie thrombosis

2 . excessive bleeding condition, ie  bleeding conditions

Thrombosis in the arteries can cause ischemia, ie bloodlessness of the tissue and organ. Examples are myocardial infarction or ischemic stroke.


Thrombosis in the veins causes venostasis. That is the accumulation of blood.

It is interesting that ...

Blood accumulation and pathological changes in blood flow are risk factors promoting thrombosis. And that in turn is the risk of developing an embolism.

Examples are diseases that can lead to embolism, namely:

  • cardiac arrhythmia
  • heart valve disease
  • cardiomyopathy

Embolism and embolization

An embolism is defined as the insertion of a moving object into a vascular bed. This object can prevent blood flow to cells, tissues, and organs. 

The embolus is trapped in the narrowed space of the vessel and partially or completely impedes the flow of blood behind it.

Embolization occurs, for example, for:

  • thrombus - a blood clot - is called a  thromboembolism
  • fat - as a fat embolism
  • air, air embolism
  • amniotic fluid
  • tumor cells
  • foreign body, when separating part of the vascular catheter

The table lists some types of thromboemolia

Place of thrombus formation Place of embolization
The veins of the lower limbs Pulmonary arteries,
embolus does not pass through the smallest vascular tangles in the lungs into the brain
The right heart Pulmonary arteries 
Varicose veins Pulmonary arteries, 
often air embolism, during surgery or injury
Left heart brain, kidneys, spleen, abdominal arteries, arteries of the lower extremities, 
thrombus formation in arrhythmias and valve defects  
Aorta brain, kidneys, spleen, abdominal arteries, arteries of the lower extremities  
Pulmonary veins brain, kidneys, spleen, abdominal arteries, arteries of the lower extremities  

It is also possible to: 

Embolization of a blood clot from thrombosis in the lower extremities to the brain.
This is the case if an atrial septal defect is present.
For more information, read the article on congenital heart defects

Read more in the article: 

What is deep vein thrombosis and what is its cause. 

What are her symptoms? How to diagnose. 

In short, about her treatment. 

What is deep vein thrombosis?

Thrombosis is a disease that can endanger human health and life. But it can also occur unnoticed or mildly. 

Deep venous thrombosis = HVT. Otherwise also phlebothrombosis.

It is characterized by a high incidence, especially in people older than 60 years. Approximately 10,000 people get sick here every year. 

The gender difference is not critical, although for men the average age of occurrence of 66 and for women 72 years. However, it also affects young people and children.

It is also dangerous due to repeated episodes. About 30% is repeated over 10 years.

Defined as: 

Deep venous thrombosis is the process of blood clot formation in the deep venous system. Which leads to a restriction of blood flow through the affected vein.

The risk is the release of a blood clot, the formation of an embolus and subsequent embolization into another part of the body.

The vast majority affect the lower limbs.

The vein involvement may be as follows:

  1. foreleg veins
  2. vena poplitea - knee vein
  3. vena femoralis - femoral vein
  4. veins of the pelvis
  5. veins of the upper limbs rarely (veins of the neck or brain)

Also read about the diseaseChronic venous insufficiency


The cause of deep vein thrombosis has a multifactorial basis. One factor cannot be identified as the main source.

As early as 1856, Rudolf Ludwig Carl Virchow, a German physician, described a triad of basic reasons for pathological blood clotting.

It is referred to as the Virchow Triad :

  1. A change in hemodynamics, stasis, or turbulence in the blood flow may be caused by:
    • vascular aneurysm
    • heart failure
    • flap error
    • limitation of limb motility for injury or after surgery, during hospitalization
    • long travel
    • mechanical oppression - swelling, tumor, obesity
    • but also other neurological and internistic diseases
  2. coagulation disorders, susceptibility to increased blood clotting - hypercoagulation
    • change in balance in the blood clotting system
    • hereditary factor
    • acquired disease 
      • chronic inflammatory diseases
      • tumor growth
      • some drugs - hormonal contraception
      • smoking
      • pregnancy and seizures = increased susceptibility to hypercoagulation
  3. vascular wall disruption  - mechanical damage to the vessel
    • injuries
    • operations
    • pathological processes near blood vessels

With an increased susceptibility to the disease, risk factors that support the onset of the problem are also mentioned. Plus, when they occur, it is better to predict the development of deep vein thrombosis and possibly prevent it.

Among the risk factors include:

  • genetic predisposition that cuts 7%
    • these are changes in coagulation factors and these important affect increased thrombosis
      • factor V Leiden mutation
      • increased coagulation factor II, VIII
      • antiphospholipid syndrome
  • immobilization for more than 72 hours
    • fixation - immobilization of the limb for injury, in plaster, splint
    • for example, in more serious illnesses and concomitant hospitalization
    • long-term diseases with mobility impairment
  • long journeys, by car, by plane - economy class syndrome, for over 4 hours
  • long sitting and standing in one position, working conditions
  • inactivity and sedentary lifestyle , lack of exercise
  • dehydration
  • smoking
  • surgical procedure, most often orthopedic or urological operations
  • hormonal changes - estrogen increases blood clotting
    • pregnancy
    • hexadecimal
    • use of hormonal contraception
  • valve errors
  • flap replacements
  • stents
  • infection
  • injury
  • tumors
  • venous catheters, mainly a central venous catheter
  • older age, especially in relation to associated diseases
  • other diseases
    • true heart failure
    • Chronic obstructive pulmonary disease
    • the ischemic disease of the lower limbs
    • ischemic heart disease
    • after a stroke
    • atherosclerosis
    • baked
    • kidneys
    • systemic lupus erythematosus
    • ulcerative colitis

Also read about the disease: Thromboembolic disease.


It is said that it usually takes place in secret, asymptomatically, ie asymptomatically or with only slight difficulty.

However, with the height of the thrombosis location, the risk of a blood clot tearing increases.

Thus, the most serious complication of phlebothrombosis is embolization. And the worst form is lung embolism. Here, too, it depends on the size and part of the closure of the pulmonary stream.

In embolization - clogging of the pulmonary trunk = reflex cessation of heart activity and death .

Microembolizations are the opposite of extensive pulmonary embolization. Recurrent episodes cause pulmonary hypertension or pulmonary heart.

Apart from embolism, the second most serious situation is the development of post-thrombotic syndrome. This is a complication that has several specifics. 

Post-thrombotic syndrome

  1. narrowing of a vein at the site of thrombosis
  2. damage to the valves of the veins of the lower limbs
  3. stagnation of blood in the lower limbs, ie its accumulation

This pathological event often further complicates a person's state of health. The limb is swollen, painful, the skin is altered or damaged by ulcers - a known term as forearm ulcers or Bérc's ulcers.

And how does deep vein thrombosis manifest?

Manifestations of HVT  - thrombosis are:

  1. swelling of the lower limb - asymmetric swelling of only one lower limb is characteristic
    • it is caused by stagnation of blood in the affected lower limb
  2. lower limb pain
    • her movement worsens
    • tension in the limb
    • feeling heavy legs
  3. restriction of lower limb mobility 
  4. increased filling of superficial veins - for the stagnation of blood in the lower limbs
  5. limb color - red tint, later cyanotic, ie blue to purple limb
  6. trophic changes, skin damage, even ulcers
  7. the skin temperature will be normal while embolizing into the artery it will be pale and cold

The arteries of the lower limb are not affected,
which indicates the normal presence of pulsations on the arteries.
If no pulsations are present,
arterial embolization should be considered.


History of diagnosis is important. The anamnesis identifies risk factors.

Such as hypercoagulation statespast thrombosis, medication, corticosteroids, and hormonal contraception. Plus with other diseases such as rheumatic diseases, inflammatory diseases, postoperative and others.

Beware of the current:
contraceptive use,
+ undiscovered genetic basis of increased blood clotting!

Awareness should be maintained in at-risk people and long-term patients. Especially with mobility impairment, immobility, and limb fixation - plaster or splint.


Traveling longer than 4 - 8 hours = risk of travel thrombosis.
This should be considered in the case of medical history.

Similarly, it is important to keep thrombosis in mind in pregnant women and sophomores.
There is a high suspicion, especially among women, who have reported a higher number of abortions in the past.

Thrombosis and hypercoagulable states = increased risk of miscarriages.

Furthermore, a physical examination is used in the diagnosis. This includes an examination of the lower limbs, temperature, color, muscle, monitoring of superficial veins, and pulsation. Some signs (Homans, plantar) can be helpful, but they do not have 100% investigative potential.

Imaging methods are important :

  1. Duplex sonography - usg examination, in which the vascular system is evaluated, color mapping of veins
  2. CT angiography
  3. MRI
  4. X-ray contrast - venography

Laboratory evidence for blood tests are  D-dimers that show the process of blood clotting. However, the specificity is low, as they occur in other conditions, such as postoperative conditions, after injuries, pulmonary embolism, inflammatory disease, and even pregnancy.

In differential diagnosis also CT of the lungs and ECHO, ECG.


The course of the disease depends on several factors. One is the extent of thrombosis. 

The most common is deep venous thrombosis in the calf sinuses - calf thrombosis. What are small venous extensions? Rarely, it may develop in the upper limb.

In the vast majority of cases, these thrombi dissolve,  so they do not lead to embolism. 

The disease may have no symptoms and is asymptomatic. Alternatively, only mild difficulties are present

Thrombosis usually occurs in only one lower limb. Depending on the disability of the limb, there are also difficulties.

The swelling may be present to a greater or lesser extent. Due to the higher degree of involvement of the forearm veins, the swelling is usually at the height of the ankle to the foreleg

A swollen limb above the knee also indicates a high deep vein thrombosis of the thigh.

The onset of swelling is relatively rapid, within a few days. It is gradually getting worse. Position and sleep do not have much effect on limb swelling.

In another primary disease, an already swollen limb swells significantly more than the other.

A difference in the circumference of the limb above 1 centimeter is highly suspicious.

It is associated with limb pain, which is aggravated by movement and change of position - standing. With thrombosis in the forelegs, it is calf pain.

Alternatively, a feeling of a severe lower limb may be present at the onset of the disease. Occasionally there are muscle cramps, tearing, a feeling of tension, and pressure.

Skin discoloration may not change. But even that depends on the extent and location of the thrombosis. The color of the skin can be red, pale, shiny, tight, or even cyanotic.

The limb temperature may be higher.

In the case of extensive thrombosis in the thigh and hip area, complete disruption of blood return from the lower limb may occur. The swelling affects the entire limb, its color is pale to mottled - cyanotic and painful. 

Then these cases are complicated by general symptoms and an increase in body temperature.

The condition is called Phlegmasia coeurlea dolens
Phlegmasia alba dolens for a pale and swollen limb.

The risk of upward thrombosis is approximately 25% of cases.

At this time, the risk of tearing off the blood clot increases, up to 50%.

It is said that it rarely develops to such a state that
it clogs the blood flow, which would jeopardize the circulation and nutrition of the lower limb.

As repeatedly stated, the risk of complication is the development of pulmonary embolism. This should only be considered in the case of higher thrombi or thrombi reaching high into the veins of the thigh.

Fluttering thrombus = thrombus partially attached to the vessel wall and partially fluttering in the bloodstream.

Long-term conditions and restriction of blood flow will cause the formation of a replacement blood circulation. So-called bypass vessels are formed - professionally collateral vascular circulation. They are visible in the thigh, hip, and abdomen. 

Sometimes it manifests itself atypically as abdominal pain. Especially in the case of high thrombosis to the involvement of blood vessels in body cavities.

How it is treated: Deep vein thrombosis

How is it treated and will medication for thrombosis help? Clotting and lifestyle measures

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