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Deep vein thrombosis

Dr Rajesh Varma

Deep vein thrombosis (DVT) is the formation of a thrombus in a deep vein, usually in the legs, which partially or completely obstructs blood flow.

DVT has an annual incidence of about 1 in 1000 people.

Continuing or intrinsic risk factors include:

  • Previous venous thromboembolism.

  • Cancer (known or undiagnosed).

  • Increasing age

  • Being overweight or obese

  • Male sex.

  • Heart failure.

  • Acquired or familial thrombophilia.

  • Chronic low-grade injury to the vascular wall (for example vasculitis, hypoxia from venous stasis, or chemotherapy).

Risk factors that temporarily raise the likelihood of DVT include:

  • Immobility.

  • Significant trauma or direct trauma to a vein (for example, intravenous catheter).

  • Hormone treatment (for example hormone replacement therapy).

  • Pregnancy and the postpartum period.

  • Dehydration.

The most serious complication is pulmonary embolism.

Typical signs and symptoms are:

Pain and swelling in one leg (occasionally both legs).

Tenderness, changes to skin colour and temperature, and vein distension.

Differential diagnosis

  • Physical trauma: muscle strain, haematoma in the muscle; rupture of the Achilles tendon;fracture.

  • Cardiovascular disorders: Superficial thrombophlebitis, Post-thrombotic syndrome

  • Venous obstruction or insufficiency

  • External compression of major veins (for example by a fetus during pregnancy, or cancer).

  • Arteriovenous fistula and congenital vascular abnormalities.

  • Acute limb ischaemia.

  • Vasculitis.

  • Heart failure 

  • Ruptured Baker's cyst

  • Cellulitis

  • Dependent (stasis) oedema.

  • Lymphatic obstruction

  • Septic arthritis

  • Cirrhosis

  • Nephrotic syndrome

  • Compartment syndrome

Assessment

Only about a third of people with clinical suspicion of deep vein thrombosis (DVT) have the condition. 

For all other people with suspected DVT, use the two-level DVT Wells score to assess the probability of a DVT.

Two-level DVT Wells score

Score one point for each of the following:

  1. Active cancer (treatment ongoing, within the last 6 months, or palliative).

  2. Paralysis, paresis, or recent plaster immobilization of the legs.

  3. Recently bedridden for 3 days or more, or major surgery within the last 12 weeks requiring general or local anaesthetics.

  4. Localized tenderness along the distribution of the deep venous system (such as the back of the calf).

  5. Entire leg is swollen.

  6. Calf swelling by more than 3 cm compared with the asymptomatic leg (measured 10 cm below the tibial tuberosity).

  7. Pitting oedema (greater than on the asymptomatic leg).

  8. Collateral superficial veins (non-varicose).

  9. Previously documented DVT.

Subtract two points if an alternative cause is at least as likely as DVT.

The risk of DVT is likely if ≥ 2 two points, and unlikely if ≤ 1 point


Management

Likely to have DVT ( two-level DVT Wells score ≥ 2 ):

  1. Refer for a proximal leg vein ultrasound scan to be carried out within 4 hours.

  2. If ultrasound scan not within 4 hours, then D-dimer testing + 24-hour dose of a parenteral anticoagulant + Arrange ultrasound scan within 24 hours


Unlikely to have DVT (two-level DVT Wells score ≤ 1):

Undertake D-dimer testing: D-dimer test is positive:

  1. Refer for a proximal leg vein ultrasound scan to be carried out within 4 hours.

  2. If ultrasound scan not within 4 hours, then D-dimer testing + 24-hour dose of a parenteral anticoagulant + Arrange ultrasound scan within 24 hours

Undertake D-dimer testing: D-dimer test is negative:
Consider an alternative diagnosis to explain symptoms.


Parenteral anticoagulants licensed for the treatment of deep vein thrombosis:

  1. Low molecular weight heparins (sc dalteparin, sc enoxaparin, and sc tinzaparin), but avoid in people with current (or history of) heparin-induced thrombocytopenia.

  2. Subcutaneous Fondaparinux, a synthetic pentasaccharide that inhibits activated factor X.

Further treatment

People with DVT require anticoagulant treatment in secondary care.

On discharge they will require maintenance treatment with an oral anticoagulant drug for at least 3 months (provided there are no contraindications such as cancer or pregnancy) and compression stockings.

Oral anticoagulants used for treatment of DVT include:
Apixaban: Dabigatran,  Edoxaban, Rivaroxaban
Warfarin (target INR 2.0-3.0)

A person with DVT should be advised to:

  1. Walk regularly after discharge from hospital.

  2. Elevate the affected leg when sitting.

  3. Refrain from extended travel, or travel by aeroplane, for at least 2 weeks after starting anticoagulant treatment