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
- 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]