see also:

• Mx of lower limb DVT
• deep venous thrombosis (DVT)
• upper limb DVT
• Ix of suspected pulmonary embolism (PE)

• patient should be briefly assessed for:
  • other differentials
    • the patient with swollen leg(s)
  • presence of risk factors
    • traditional risk factors
      • cancer (including polycythaemia rubra vera), pelvic mass, hormonal Rx, recent surgery/immobilisation, pregnancy, PH or FH DVT/PE, combined oral contraceptive pill (OCP), prolonged flights
    • genetic factors - see NEJM
      • see thrombophilia
        • eg. protein C defic - emedicine.com
    • COVID-19 coronavirus (2019-nCoV / SARS-CoV-2)
    • rheumatoid arthritis
  • evidence of pulmonary embolism, which if suspected should be managed accordingly.
• determine pre-test probability of DVT as this will help determine which Ix pathway:
  • Wells score (ref):
    • score 1 for each item, except minus 2 for the last:
    • active cancer with treatment, including palliative, in last 6 months
      • 4-7x risk of DVT, and appears to be especially if on a high tryptophan or protein (eg. meat) diet via Indoleamine 2,3-Dioxygenase 1 activity and increased production of kynurenine (Kyn) ¹⁾
    • paralysis, paresis or recent plaster immobilisation of legs
    • bedridden for > 3 days or major surgery within last 12 weeks
    • localised tenderness along distribution deep venous system
    • entire leg swollen
    • calf swelling > 3 cm compared to normal measured 10 cm below tibial tuberosity
    • pitting oedema greater in symptomatic leg
    • non-varicose, collateral superficial veins
    • PH documented DVT
    • alternative diagnosis at least as likely DVT (scores minus 2)
• Wells score 0 or less:
  • probability of DVT < 5%
  • a negative D-Dimer will be sufficient to exclude DVT unless patient has cancer or PH of DVT
  • if D-Dimer positive then USS and if this is negative then DVT excluded, if USS +ve then Rx as for DVT.
• Wells score > 0:
  • Wells score 3 or higher gives probability of DVT ~50%
  • Wells score 1-2 gives probability of DVT ~17%
  • D-Dimer is NOT useful as a negative test still does not exclude a DVT adequately
  • patient should be referred for USS, preferably same day, or if not possible within 24hrs with consideration for starting enoxaparin 1mg/kg bd s/c if DVT is likely.
  • if mild symptoms, then these patients can usually be discharged for US next day then review.
  • if USS negative, then perform D-Dimer and if this is negative then DVT excluded, if positive then rpt USS in 1 week.
  • if USS +ve then Mx as for DVT
  • patients with extensive symptoms (ie. clearly above knee), should be started on enoxaparin and admitted pending USS confirmation - consider admit to a short stay observation unit (SSU) if likely to go home within 24hrs.