🧭 When to suspect
Suspect a deep vein thrombosis (DVT) in any adult with unilateral leg symptoms, classically in the calf:
• swelling
• pain
• tenderness
• warmth or redness
A DVT is a thrombus in a deep vein; the danger is that:
• the clot may extend proximally
• it may embolise to the lungs as a pulmonary embolism (PE), which can be fatal
The decisive distinction is proximal versus distal disease. A proximal DVT (at or above the popliteal trifurcation) is the clot that matters most – it is the source of virtually all clinically significant PE and the focus of NICE management.
In primary care, you need to:
• stratify probability with the 2-level DVT Wells score
• arrange the right test in the right order
• never miss a PE or a limb-threatening leg
In all non-pregnant adults with suspected DVT, calculate the 2-level DVT Wells score first – it decides whether the next step is an ultrasound or a D-dimer.
• The score is not validated in pregnancy.
• Pregnant or recently postpartum women follow a separate pathway.
| 2-level DVT Wells score – clinical feature | Points |
|---|---|
| Active cancer (treatment ongoing, within 6 months, or palliative) | 1 |
| Paralysis, paresis or recent plaster immobilisation of the lower limb | 1 |
| Recently bedridden ≥ 3 days, or major surgery within 12 weeks (general/regional anaesthesia) | 1 |
| Localised tenderness along the distribution of the deep venous system | 1 |
| Entire leg swollen | 1 |
| Calf swelling ≥ 3 cm larger than the asymptomatic side | 1 |
| Pitting oedema confined to the symptomatic leg | 1 |
| Collateral superficial veins (non-varicose) | 1 |
| Previously documented DVT | 1 |
| An alternative diagnosis is at least as likely as DVT | −2 |
| DVT likely | ≥ 2 points |
| DVT unlikely | ≤ 1 point |
Key risk factors to weight clinically:
• active cancer
• recent surgery, trauma or immobility (including long-haul travel and lower-limb plaster)
• oestrogen-containing contraception or HRT
• pregnancy/puerperium
• obesity
• increasing age
• a personal or family history of venous thromboembolism (VTE) or known thrombophilia
Source: NICE NG158 · NICE QS201
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