Deep vein thrombosis

Overview

•Virchow's triad - venous stasis, endothelial injury, hypercoagulability; most DVTs involve >1 element

•Calf veins most common site; proximal propagation (popliteal, femoral) significantly increases PE risk

Risk factors

Immobility / prolonged travel

Recent surgery or trauma

Malignancy

Combined OCP / oral HRT

Pregnancy / gravid uterus

Thrombophilia (e.g. Factor V Leiden, protein C/S deficiency)

Antiphospholipid syndrome

Dehydration / heart failure

IV catheters / chemotherapy

Previous VTE

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Oral HRT and combined OCP increase VTE risk; transdermal HRT does NOT carry the same risk - a classic exam discriminator. Consider stopping prior to major surgery.

Presentation

•Unilateral calf/leg pain, swelling, pitting oedema, erythema and warmth, dilated superficial veins

•Calf circumference >3 cm difference (measured 10 cm below tibial tuberosity) is significant

•Many DVTs are asymptomatic and first present as PE

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Bilateral leg swelling should prompt an alternative diagnosis first (heart failure, hypoalbuminaemia, chronic venous insufficiency). Homan's sign is unreliable - do not use it to confirm or exclude DVT.

Investigations

•Two-level DVT Wells score - stratifies into DVT likely (≥2) or DVT unlikely (<1); guides whether to image first or use D-dimer

•D-dimer - sensitive (~95%) but non-specific; negative result excludes DVT when Wells score is low; false positives: pregnancy, malignancy, infection, surgery, heart failure, recent trauma

•Proximal leg Doppler ultrasound - first-line imaging; non-compressibility of the vein is the diagnostic criterion

•Repeat ultrasound at 6-8 days - if initial ultrasound negative but D-dimer positive and Wells score suggests DVT likely

•Thrombophilia testing - consider in unprovoked/recurrent DVT, strong family history, or unusual site; do NOT test during acute thrombosis or anticoagulation

•Malignancy screen - consider in unprovoked DVT: clinical examination, FBC, LFTs, urinalysis as minimum

Differential diagnosis

Management

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If DVT is suspected and there will be a delay to imaging, start anticoagulation immediately - do not wait for imaging confirmation.

•Anticoagulation is the mainstay of treatment - typically a DOAC (rivaroxaban or apixaban) as first-line per NICE NG158

•Unprovoked DVT carries higher recurrence risk - consider longer anticoagulation and investigation for underlying malignancy or thrombophilia

Prevention

•All inpatients should be assessed for VTE risk on admission and individual bleeding risk weighed against benefit of prophylaxis (NICE NG89)

•First-line pharmacological: enoxaparin (LMWH) - start as soon as possible and within 14 hours of admission

•First-line mechanical: anti-embolic compression stockings - used alongside LMWH in surgical patients; contraindicated in significant peripheral arterial disease, severe leg oedema, or skin breakdown

•Second-line mechanical: intermittent pneumatic compression devices - if stockings contraindicated or for additional prophylaxis in high-risk surgical patients

•Early mobilisation and adequate hydration - important for all inpatients

Complications

•Pulmonary embolism - most life-threatening; massive PE causes cardiovascular collapse; smaller PE: pleuritic chest pain, dyspnoea, haemoptysis

•Post-thrombotic syndrome - up to 50% within 2 years; chronic venous obstruction and valve destruction → persistent venous hypertension → oedema, pain, dermatitis, venous ulceration

•Recurrent DVT - higher risk in unprovoked DVT and thrombophilia