Deep Venous Thrombosis

Deep Venous Thrombosis (DVT) is a commonly discussed medical condition. It is a condition where a blood clot forms in the deep venous system of the lower legs. DVT is the third commonest cardiovascular disease. Around 20% of DVTs occur post surgery. 25% of DVTs are associated with cancers and 50% happen due to unknown reasons.

Anatomy of Deep Venous System

The aetiology of DVT is summarised by Virchow's triad of:
-Hypercoagulability (increased tendency to form blood clots)
-Venous Flow Stasis
-Vessel wall damage


Patients who have DVT usually complain of:
-calf pain
-calf swelling
-redness around the lower leg
-unilateral pitting oedema
-low grade fever


Sometimes the lower leg can be bluish (cyanotic), severely painful and swollen in a condition described as Phlegmasia Caerulia Dolens. Phlegmasia Alba Dolens describes a pale, painful, swollen limb.


Conditions which increase the risk of DVT are:
-increasing age
-immobility
-pregnancy
-patients who are diagnosed with cancers
-patients who are on oral contraceptive pills (combined progestrone & oestrogen)
-patients who are on hormone replacement therapy
-obesity
-patients with inflammatory bowel disease
-patients who are planned for knee, pelvic & hip surgeries
-patients with heart failure


Investigations for patients with DVT include:
-Duplex ultrasound scans: - 95% sentitive & specific
-Venography: - can be both diagnostic & therapeutic
-Magnetic Resonance Venography
-Impedence Pletysmography
-Spiral CT-scan / CT Pulmonary Angiography: to rule out Pulmonary Embolism

Image at Left: Deep Vein Thrombosis

Image at Right: Embolus propagating

Treatment for DVT aims to stop further clot formation, to break down the existent clot (fibrinolysis) and to prevent pulmonary embolism. Pulmonary embolism is the propagation of a blood clot from the lower leg into the smaller veins of the lungs. This is a potentially deadly complication of DVT where 10% of patients with symptomatic pulmonary embolism die within the first hour. 


Treatment options include:
-intravenous Heparin infusion
-oral Warfarin tablets
-subcutaneous Low Molecular Weight Heparin (eg enoxaparine) injection
-percutaneous mechanical thrombectomy
-catheter directed thrombolysis
-insertion of an Inferior Vena Cava filter: for prevention of pulmonary embolism in high risk patients


The complications of DVT are:
-pulmonary embolism
-propagation of clot
-chronic venous insufficiency
-varicose veins
-venous ulcers