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

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%.

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Featured Image: Right leg DVT [Wikimedia Commons]