Over a century ago, Rudolf Virchow described 3 factors that are critically important in the development of venous thrombosis: Virchow triad are;

  1. Venous stasis    : Anything obstructing or slowing flow of venous blood
  2. Activation of blood coagulation: Biochemical imbalance between circulating factors
  3. Vein damage    : Intrinsic or extrinsic

Predisposing or common risk factors identified are;

  • Diseases:
    • Hypertension, Diabetes, Neurological diseases, Stroke, Myocardial infarction, Heart failure, Inflammatory bowel disease, Previous DVT, COPD
    • Malignancy (abnormal coagulation, pressure, chemotherapy) especially genitourinary cancer are of highest risk
  • Lifestyle:
    • Immobilization > 3days
    • Obesity
  • Treatment:
    • Surgery: Orthopaedic, Cancer
    • Ventilator dependent
  • Hormones:
    • High level of homocysteine in males
    • Oral contraceptives and hormone replacement therapy for postmenopausal
  • Trauma
  • Pregnancy and postpartum period
  • Anatomical variations