Deep Venous Thrombosis: The Usual Suspects

Documented Risk Factors — most will have more than one underlying condition ≡ secondary VTE

  • immobilisation or prolonged bed rest (incl. hospitalisation) 52%
  • recent surgery 42%
  • obesity
  • prior VTE (especially < 50 years old)
  • lower extremity trauma 6%
  • malignancy 48%
  • OCP / HRT
  • Pregnant or post-partum
  • H/O Stroke
  • Family History
    • RR 2.27 with one affected siblings
    • RR 51.9 with two affected siblings
  • age > 75
  • presence of acute infectious disease
  • collagen vascular disease
  • myeloproliferative disease
  • atherosclerotic disease
  • nephrotic syndrome
  • drugs which can induce anti-phospholipid antibody syndrome (APAS)
    • hydralazine
    • procainamide
    • phenothiazines
  • heart failure

Coagulation Cascade [Wikimedia Commons]
Findings — any abnormality should be investigated aggressively

  • Differential in calf girth
  • absence of calf swelling
  • phlegmasia cerulea dolens
  • DRE + FOBT
  • female pelvic examination
  • FBC (platelets)
  • coagulation studies
  • RFT
  • Urinalysis
  • ± PSA

Only 1/5th to 1/3rd of those suspected of having a DVT have the disease:

  • muscular strain / tear (or twisting injury to leg) — 40%
  • leg swelling in paralysed limb — 9%
  • lymphangitis (lymph obstruction) — 7%
  • chronic venous insufficiency — 7%
  • popliteal (Baker’s) cyst — 5%
  • cellulitis — 3%
  • knee joint pathology — 2%
  • ?? unknown — 26%
  • drug-induced leg oedema, e.g. CCB

The age-standardised incidence of first-time VTE is 1.92 per 1,000 person-years.

Diagnosis is made by:

  • Compression Ultrasonography — 94% PPV
  • D-dimer
  • contrast venography
  • MRI / CT scan
  • impedance plethysmography

If the initial study is negative and the clinical suspicion is high, a repeat study should be obtained on Day 5-7 — unless a complete extended lower extremity ultrasound scan was performed the first instance (although this requires specialised instruments and is highly operator dependent).

  • Pre-test probability (e.g. Wells score, Hamilton, Amuse)
  • + USS
  • + D-dimer

A low Wells score (pre-test probability) especially if the D-dimer is low has a NPV of 96%.

A high Wells score (pre-test probability) has a PPV of ∼ 75%.


Featured Image: Right leg DVT [Wikimedia Commons]

Advertisements