Deep Vein Thrombosis


Overview Deep vein thrombosis (DVT) is the formation of a blood clot in a vein deep under the skin 25-50% of surgical patients and many non-surgical patients. 65% of DVT are below the knee are symptomatic and rarely embolism to the lung. There are many causes of DVT.


blood clot 
blood clot that forms in a vessel and remains there
Deep Vein Thrombosis (DVT): 
Formation of a blood clot in one of the deep veins of the body, usually in the leg
Pulmonary Embolism (PE):
 occurs most often from a disloged thrombus from teh lower limb (DVT). The embolyus travels towards the lung and becomes lodged in the pulmonary artery resulting in infarction of the lung tissue.
Venous Thromboembolism (VTE): 
Formation, development, or existence of a blood clot or thrombus within the venous system that has/potential to embolize.

Signs and Symptoms

Clinical Presention DVT usually affects the veins in the legs, notably the calf.Sands

  • Asymmetrical pain and/or tenderness
  • Asymmetrical warmth/ erythema
  • Asymmetrical swelling

Signs of Pulmonary embolism (complication of DVT)

  • Breathlessness
  • Chest pain
  • Coughing
  • Tachycardia
  • Haemoptysis


Wells Criteria

Clinical features Score
Active cancer   1
Paralysis, paresis, or recent cast immobilization of the lower extremities 1
Recently bedridden for ≥ 3 days, or major surgery within the previous 12 weeks requiring general or regional anesthesia 1
Localized tenderness along the distribution of the deep venous system 1
Entire leg swelling 1
Calf swelling at least 3 cm larger than that on the asymptomatic side 1
Pitting edema confined to the symptomatic leg 1
Collateral superficial veins (non-varicose) 1
Previously documented deep vein thrombosis 1
Alternative diagnosis at least as likely as deep vein thrombosis 2

Wells Scoring System - help tailor investigations

  • Low probability: 0
  • Moderate probability: 1-2
  • High probability: 3-8

Differential Diagnosis

  • Cellulitis
  • Thrombophlebitis
  • Arthritis
  • Asymmetric peripheral oedema secondary to heart failure, renal disease or liver disease
  • Haematoma
  • Lymphoedema
  • Ruptured backers cyst
  • Varicose veins

Investigation and Diagnosis

Think D-dimer assay is only useful if it is negative; it helps in ruling out DVT



  • Duplex ultrasound
  • Venography (phlebography) - Gold standard


All comes down to Virchow's Triad. Any change to Virchows triad increases the risk of VTE.

Virchows Triad: Hypercoagulability, Vessel wall injury, Stasis



  • Malignancy
  • Surgery
  • Trauma
  • Oral contraceptive pill
  • Genetic
  • Antiphosphlipid syndrome
  • Hyper homocysteine level
Inherited Thombophilias
Factor 5 leiden mutation
Pro-thrombin gene mutation
Protein S deficiency
Protein C deficiency


  • Immobility, e.g. after surgery
  • Pregnancy
  • Obesity
  • Heart failure
  • Cast on the leg
  • Extended travel in plane/vehicle

Endothelial injury

  • Inflammation
  • Previous thrombosis
  • Atherosclerosis
  • Fracture


The aim of treatment is to prevent PE, reduce morbidity and prevent or minimise the risk of developing the postphlebitic syndrome

  • Pain management - analgesia +/- opioids
  • Anticoagulation
    • Low risk bleeding - Low molecular weight heparin (enoxaparin 1.5mg/kg SC daily)
    • Average risk bleeding - Unfractionated heparin


Clinical situation Duration
VTE provoked by transient major risk factor 3 months
Distal unprovoked DVT or PE 3 months
First unprovoked proximal DVT or PE 6 months
First unprovoked VTE plus
  • Active malignancy
  • Multiple thrombophilias
  • Antiphospholipid syndrome
Recurrent unprovoked VTE Indefinite

Complications and Prognosis


  • Acute
  • Chronic
    • Post thrombotic syndrome
    • Chronic venous insufficiency




  • Identify patient at risk
  • Prevent Dehydration
  • Mechanical prophylaxis
    • Intermittent Pneumotic Compression
    • Calf compression stockings
  • Encourage movement
  • Exercise
  • Quit smoking
  • Medication - Warfarin to therapeutic dose INR 2-3 OR NOAC of choice
  • IVC filter

Prevention in surgery

  • High Risk - LMWH (40mg daily) + mechanical prophylaxis
    • Orthopaedic Surgery
    • Major trauma
    • Fracture
    • Major surgery >40yo
  • Medium Risk - LMWH (20mg daily) + mechanical prophylaxis
  • Low Risk - Consider LMWH + mechanical prophylaxis
    • All other surgery
Remember Make sure there are no contraindications for LMWH and Mechanical prophylaxis