History and exam
Key diagnostic factors
common
calf swelling
Unilateral leg and thigh swelling can be assessed by measuring the circumference of the leg 10 cm below the tibial tuberosity. If there is a difference in circumference, DVT is more likely. A difference of >3 cm between the extremities is a component of the Wells score.[12]
localised pain along deep venous system
Localised pain can be assessed by gently palpating along the path of the deep venous system from groin to adductor canal and in the popliteal fossa. This is a component of the Wells score.
Significant pain, particularly in combination with marked swelling and cyanosis, is a sign of phlegmasia cerulea dolens (PCD). If you suspect PCD, start immediate treatment; do not wait for the results of investigations because this is a life- and limb-threatening emergency.[81] See Phlegmasia cerulea dolens under Management recommendations.
presence of risk factors
Ask about significant risk factors, which include:
Recently bedridden for 3 days or more, or major surgery within 12 weeks requiring general or regional anaesthesia[12][26]
Active cancer (treatment ongoing, within 6 months, or palliative)[12][24][25][26][27]
Paralysis, paresis, or recent plaster immobilisation of the lower extremities[12][18][26][27]
Hereditary thrombophilia (e.g., factor V Leiden, prothrombin gene G20210A mutation, protein C or protein S deficiency)
Presence of medical comorbidities
Certain drugs (e.g., oestrogen-containing oral contraceptives).
positive Wells score
Assess the clinical probability of DVT using the Wells score (unless the patient is pregnant; see Suspected DVT in pregnancy under Diagnosis recommendations).[12][26][27] [ Modified Wells score for deep vein thrombosis (DVT) Opens in new window ]
There are several risk assessment models available to assess the clinical probability of DVT; however, the Wells score provides a reproducible method to determine the clinical probability of DVT and is the most widely accepted and validated pretest probability tool used in diagnostic algorithms for DVT.[26][85][86]
The two-level Wells score categorises patients as ‘DVT likely’ (Wells score ≥2) or ‘DVT unlikely’ (Wells score <2).[12][26][27]
A three-level iteration of the Wells score (where patients are categorised into low, moderate, or high clinical likelihood of DVT) is available but the two-level score is generally preferred in practice.[26][27]
Practical tip
The Wells score may underestimate the probability of DVT in certain patient groups, such as patients who misuse intravenous drugs.[87] In practice, categorise patients who inject drugs into a femoral vein as ‘DVT likely'.
Wells score elements | Score |
|---|---|
Active cancer (any treatment within past 6 months) | 1 |
Calf swelling where affected calf circumference measures >3 cm more than the other calf (measured 10 cm below tibial tuberosity) | 1 |
Prominent superficial veins (non-varicose) | 1 |
Pitting oedema (confined to symptomatic leg) | 1 |
Swelling of entire leg | 1 |
Localised pain along distribution of deep venous system | 1 |
Paralysis, paresis, or recent cast immobilisation of lower extremities | 1 |
Recent bed rest for >3 days or major surgery requiring regional or general anaesthetic within past 12 weeks | 1 |
Previous history of DVT or pulmonary embolism | 1 |
Alternative diagnosis at least as probable | -2 |
Clinical probability* | |
DVT unlikely | <2 (probability, 15%) |
DVT likely | ≥2 (absolute risk is approximately 40%) |
*Two versions of the risk assessment model have been validated: two categories (DVT unlikely or likely) or three categories (low, intermediate, or high clinical probability. The simplified version (producing two score categories) is presented as it is likely the easiest to use in clinical settings.
Use the Wells score in combination with a diagnostic algorithm.[12][26][27] See Diagnostic algorithm under Diagnosis recommendations for more information. The National Health Institute for Health and Care Excellence (UK) recommends the following:[12]
If the patient is categorised as ‘DVT likely’, organise a venous ultrasound, with the result available within 4 hours.[12][60] Start therapeutic anticoagulation if proximal DVT is confirmed[12]
If the patient is categorised as ‘DVT unlikely’, order a D-dimer with the result available within 4 hours[12]
See Investigations for next steps, or if the results of investigations aren’t available within 4 hours.
If a whole-leg ultrasound confirms distal (calf) DVT, check your local protocol for advice on whether and how to start anticoagulation; guidelines vary in terms of their recommendations. In the UK, common practice is to start anticoagulation unless the patient has a high risk of bleeding or the DVT is not extensive (<5 cm).
uncommon
redness and warmth
Symptoms of DVT.[83]
coolness
A symptom of DVT.
Other diagnostic factors
common
asymmetric oedema
Presence of oedema worse on leg with suspected DVT.
prominent superficial veins
Dilated superficial veins over foot and leg (not varicose veins) are a sign of DVT.
uncommon
swelling of the entire leg
Increases pretest probability of diagnosis of DVT. A difference of >3 cm between the extremities is a component of the Wells score.[12]
Marked swelling, particularly in combination with significant pain and cyanosis, is a sign of phlegmasia cerulea dolens (PCD). If you suspect PCD, start immediate treatment; do not wait for the results of investigations because this is a life- and limb-threatening emergency.[81] See Phlegmasia cerulea dolens under Management recommendations.
cyanosis
Cyanosis (blue discoloration), particularly in combination with marked swelling and significant pain, is a sign of phlegmasia cerulea dolens (PCD). If you suspect PCD, start immediate treatment; do not wait for the results of investigations because this is a life- and limb-threatening emergency.[81] See Phlegmasia cerulea dolens under Management recommendations.
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