Deep vein thrombosis

Deep vein thrombosis is the formation of a blood clot in a deep vein, usually in a leg. It requires prompt diagnosis and treatment to prevent the clot from growing, recurring or travelling to the lungs.

What is deep vein thrombosis?

Deep veins carry blood from the limbs back to the heart. Deep vein thrombosis, known by its acronym DVT, occurs when a clot — or thrombus — forms inside one of these veins. Most occur in the legs, although they can also affect the arms or other areas.

The thrombus can partially or completely obstruct the return of blood. This increases the pressure within the vein and can cause pain, swelling and changes to the skin. DVT and pulmonary embolism are part of the same condition known as venous thromboembolism.

A pulmonary embolism occurs when a piece of the clot breaks away, travels through the bloodstream and reaches an artery in the lungs. Not all cases of thrombosis lead to this complication, but preventing it is one of the main aims of treatment.

What symptoms can it cause?

The most common symptom is recent swelling in one leg. It can affect the foot, ankle, calf or the entire leg, depending on the location and extent of the blood clot. The following may also occur:

• Pain or tenderness.

• A feeling of tightness or heaviness.

• Increased skin temperature.

• Redness or a change in colour.

• Increased visibility of some superficial veins.

The pain may be localised in the calf or extend up into the thigh. Its intensity varies and is not always related to the size of the thrombus. These symptoms may also be caused by a muscle injury, an infection, joint inflammation, venous insufficiency or lymphoedema. Therefore, whilst they raise suspicion, they do not confirm the diagnosis.

How is deep vein thrombosis confirmed?

The diagnosis is based on a combination of symptoms, risk factors and tests. Depending on the clinical probability, a D-dimer test, a venous ultrasound scan or both tests may be used, following a specific sequence.

When urgent assessment is required

Deep vein thrombosis can lead to complications if part of the clot travels to the lungs or if the blockage in the vein is very extensive. For this reason, certain symptoms require immediate medical attention. An urgent assessment should be sought if the following occur:

• Sudden difficulty breathing.

• Chest pain, especially when breathing in.

• Coughing up blood.

• Fainting or a strong feeling of faintness.

• Heart palpitations accompanied by a general feeling of unwellness.

• A sudden worsening of symptoms.

These symptoms may indicate a pulmonary embolism and require immediate assessment. Prompt medical attention is also required if the leg shows severe swelling, intense pain, a bluish discolouration, coldness or loss of sensation. These signs may indicate extensive venous obstruction affecting blood flow to the limb.

What causes deep vein thrombosis?

Blood normally flows through the veins without clotting. A thrombus can form when blood flows more slowly, the vein wall is damaged, or the blood is more prone to clotting. These mechanisms are known as Virchow’s triad.

All three factors do not necessarily have to be present in every person. In many cases, there is a recognisable triggering factor, whilst in others, thrombosis occurs without any obvious cause.

Main risk factors

Temporary medical conditions

The risk increases during periods when mobility is reduced or blood clotting changes temporarily. These include:

• Surgery.

• An injury.

• A plaster cast.

• Prolonged bed rest.

• Pregnancy and the postnatal period.

• Certain oestrogen-based hormone treatments.

Orthopaedic, oncological and abdominal surgery are associated with a particularly high risk.

Chronic diseases or conditions

Certain tumours and their treatments increase the blood’s tendency to clot. The risk may also be higher in people with obesity, heart failure, nephrotic syndrome, inflammatory diseases or certain haematological disorders. The extent of the risk depends on the specific condition and how it interacts with other factors.

Previous individual risk

A history of DVT or pulmonary embolism increases the likelihood of a further episode. Age and certain inherited or acquired coagulation disorders may also play a role.

The latter are known as thrombophilias. They are not routinely tested for in everyone, as testing is only useful when it can influence treatment or family counselling.

Prolonged travel

Sitting for many hours can modestly increase the risk, particularly if other predisposing factors are present. A long journey does not carry the same risk as surgery, a hospital stay or strict immobilisation.

Induced and uninduced DVT

Proven DVT is defined as DVT associated with an identifiable factor, such as surgery, significant immobilisation, trauma, pregnancy, the postpartum period, hormonal treatment or active cancer. It is termed an unprovoked DVT when no clear trigger can be identified. This distinction influences the duration of treatment and the risk of the thrombosis recurring.

An unprovoked DVT does not necessarily mean that there is an underlying cancer. The assessment is tailored to the patient’s age, symptoms, physical examination and recommended screening programmes, without automatically carrying out extensive testing.

How it is diagnosed

Based on the patient’s medical history and physical examination, the likelihood of DVT is assessed, usually using a validated scoring system such as the Wells score. Depending on the result, a decision is made as to whether a D-dimer test, a venous ultrasound scan, or both tests are required.

D-dimer

D-dimer is a fragment whose levels may rise when the body forms and breaks down fibrin, a protein involved in blood clotting. Its main purpose is to help rule out DVT when the clinical probability is not high. A normal result, interpreted in the appropriate context, makes thrombosis unlikely.

However, an elevated level does not confirm the diagnosis, as it can also rise with age, inflammation, pregnancy, recent surgery or numerous acute illnesses. In older people, an age-adjusted cut-off may be used, in accordance with clinical guidelines.

Venous ultrasound

Venous ultrasound, or Doppler ultrasound, is the main imaging test used to investigate a possible DVT in the legs. It allows the veins to be visualised and checks whether any segment is obstructed by a thrombus. The test does not use radiation and is usually carried out quickly.

In some cases, an initial normal ultrasound scan does not fully rule out the condition. If suspicion persists or the results are inconclusive, it may be necessary to repeat the scan after several days. When the thrombosis is located in areas that are difficult to visualise, such as the pelvis, or affects other parts of the body, additional imaging techniques may be used.

Location and extent

The position of the blood clot affects the risk and may influence treatment.

Proximal DVT

This affects veins at or above the knee. It carries a higher risk of pulmonary embolism and usually requires anticoagulation.

Distal DVT

This is confined to the deep veins of the calf. Some cases require anticoagulant treatment. In selected cases, where symptoms are mild and the risk of progression is low, a decision may be made to carry out serial ultrasound scans to check that the clot is not spreading. The decision depends on the extent of the clot, the symptoms, risk factors and the feasibility of reliable follow-up.

What is the treatment for deep vein thrombosis?

The aim is to prevent the clot from growing, reduce the risk of pulmonary embolism and prevent further thrombosis. Many stable patients with uncomplicated DVT can be treated at home, provided they are able to take their medication correctly and there is no high risk of bleeding.

Hospital admission may be necessary in the event of a significant pulmonary embolism, extensive thrombosis, severe pain, a high risk of bleeding or serious associated conditions.

Anticoagulation

Anticoagulants reduce the blood’s ability to form and enlarge clots. They do not ‘thin the blood’ or dissolve the clot immediately. The body needs time to reorganise it, reduce its size and partially restore venous flow.

Direct oral anticoagulants are a common option for many adults. In other situations, heparins or vitamin K antagonists may be used. The choice depends on the clinical situation, kidney function, pregnancy, cancer, certain coagulation disorders, drug interactions and the risk of bleeding.

The treatment must be taken regularly. Missing doses may reduce protection against the clot spreading or recurring.

Duration of treatment

There is no standard duration of treatment for everyone. Anticoagulation is usually continued for several months. Afterwards, a decision is made as to whether to discontinue or continue treatment. The decision depends on whether the DVT was caused by a specific trigger, whether the trigger has resolved, the location of the DVT, the patient’s medical history, and the balance between the risk of recurrence and the risk of bleeding.

An improvement in symptoms does not mean that treatment can be stopped before the recommended date.

Mobility and symptom management

Once treatment has begun, and provided the patient’s general condition allows it, walking is usually safe and recommended. Routine bed rest is not advised for fear that the clot might break loose. Activity should be adjusted according to pain and swelling. A return to more strenuous exercise should be gradual.

Compression stockings may help relieve heaviness, pain or swelling in some people. They are not routinely prescribed to all patients for the sole purpose of preventing post-thrombotic syndrome. Their use should be tailored to symptoms, arterial circulation and individual tolerance.

Interventional treatments

Thrombolysis uses medicines capable of dissolving the clot more rapidly. Thrombectomy allows the clot to be removed via a vascular procedure. These techniques are not used in most cases of DVT, as they may increase the risk of bleeding and their benefit depends on the specific situation.

They may be considered in cases of extensive thrombosis, severe and recently onset symptoms, low haemorrhagic risk, or when the limb is at risk. The vena cava filter is also not used routinely. It is mainly reserved for exceptional situations where anticoagulation is not possible.

Progression and possible complications

Many people improve gradually over the first few weeks. The swelling may take longer to subside and, in some cases, residual changes in the vein may persist. The fact that an ultrasound scan continues to show residual material or abnormalities does not necessarily mean that the treatment has failed.

Pulmonary embolism

This is the main acute complication. It occurs when a piece of the thrombus travels to the lungs and blocks a pulmonary artery. The risk decreases significantly once appropriate anticoagulation has been started, although it does not disappear immediately.

Post-thrombotic syndrome

This may develop months or years later due to residual damage to the veins and their valves. It can cause swelling, a feeling of heaviness, pain and skin changes. In advanced cases, venous ulcers may develop. Not all persistent symptoms are indicative of this syndrome, so it is advisable to monitor the patient’s progress and rule out other causes.

Recurrence

A person who has had a DVT may develop another thrombosis in the future. The risk depends on the cause of the first episode, the persistence of predisposing factors, medical history and the duration of anticoagulation therapy.

How to reduce the risk of further thrombosis

Not all DVT cases can be prevented. In the event of hospitalisation, major surgical procedures or prolonged immobilisation, the healthcare team will assess the need for early mobilisation and, where indicated, anticoagulant or mechanical measures.

During long journeys

Most people can reduce their risk by getting up periodically, walking whenever possible and moving their ankles and legs. Compression stockings or preventive medication are only considered for people at high risk and following an individual assessment.

After a DVT

To reduce the likelihood of recurrence, it is important to take the anticoagulant correctly, attend follow-up appointments and inform your healthcare team of any future surgery, periods of immobilisation, pregnancies or hormonal treatments. Maintaining appropriate physical activity and a healthy weight promotes general health, although a DVT should not be interpreted as a consequence of inadequate self-care.

Which specialists treat deep vein thrombosis

The assessment and management of deep vein thrombosis may involve different specialists depending on the location of the clot, risk factors, progression and treatment requirements.

Emergency Department and General Practice are usually involved in the initial assessment and in identifying situations that require immediate investigation.

Specialists in angiology and vascular surgery assess venous circulation, the extent of the thrombosis and the need for specific investigations or procedures. Depending on the case, specialists in Internal Medicine and Haematology may also be involved, particularly when it is necessary to investigate predisposing factors, adjust anticoagulation therapy or assess the risk of recurrence.

Interventional procedures are reserved for selected situations in which the location, extent of the thrombus or impact on the limb justify a specific approach. During pregnancy, treatment is usually coordinated with the Gynaecology department and with the specialists responsible for anticoagulation.

At our hospital, within the Department of Angiology and Vascular Surgery, we have an Abdominal Compression Syndromes and Venous Thrombosis Unit, dedicated to the specialist assessment of these conditions and the follow-up of cases requiring more complex vascular investigation.

Life after a DVT

Most people can gradually resume their usual activities. During the first few weeks, it is common to experience persistent swelling, tightness or tiredness in the leg. Improvement may be gradual.

Recovery and activity

Walking is usually part of the recovery process. Returning to work depends on your symptoms and the type of work involved. Exercise is resumed gradually, taking into account any pain and the risk of injury. Whilst taking anticoagulants, contact sports or activities with a high risk of falling may need to be adapted.

Taking anticoagulants safely

It is important to follow the prescribed dose and schedule. Before taking any new medication, including anti-inflammatories or herbal remedies, you should check whether it might increase the risk of bleeding or alter the effect of your anticoagulant.

You should also inform your healthcare team about your treatment before any operation, tooth extraction or invasive procedure. You must not stop taking your anticoagulant on your own initiative. If it is necessary to stop taking it, your healthcare team will advise you on how to do so.

When to seek advice about possible bleeding

You should seek prompt medical assessment if you experience:

• Bleeding that won’t stop.

• Vomiting blood.

• Black stools.

• Urine containing a large amount of blood.

• Very heavy menstrual bleeding.

• Severe weakness.

• Severe headache, especially following a blow to the head.

Minor bruising or slight bleeding may occur during treatment, but you should also mention this if it is recurrent or causes you concern.

Travel, contraception and pregnancy

Travelling may be possible when the person is clinically stable, but the timing must be assessed on a case-by-case basis depending on the extent of the thrombosis, the symptoms and the stability of the treatment. Following an oestrogen-related thrombosis, the choice of contraception or hormone therapy should be reviewed with a healthcare professional.

Anyone who is pregnant, planning a pregnancy or in the postpartum period requires specific monitoring, as some anticoagulants are not used during these stages.