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Deep vein thrombosis

SNOMED: 1141709008826 words•Updated 03/03/2026
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Exam Tips

  • In UK exams, start with Wells score then follow the imaging/D-dimer pathway rather than ordering all tests at once.
  • A unilateral calf difference >3 cm supports DVT probability and is a specific Wells item.
  • Pregnant or postpartum (within 6 weeks) patients with suspected DVT need same-day specialist assessment; LMWH is preferred while investigating.
  • Know first-line treatment doses: apixaban 10 mg BD for 7 days then 5 mg BD; rivaroxaban 15 mg BD for 21 days then 20 mg OD.
  • Always mention baseline FBC, renal/liver function, PT/APTT and bleeding-risk review before/soon after starting anticoagulation.
  • If chest pain, dyspnoea, or haemoptysis develops in a DVT patient, treat as possible PE emergency.

Definition

Deep vein thrombosis (DVT) is the formation of a thrombus within the deep venous system, most commonly in the legs or pelvis, causing partial or complete obstruction of venous flow. It is part of venous thromboembolism (VTE) and may be provoked (recent transient risk factor) or unprovoked. The key clinical danger is embolisation to the pulmonary arteries, producing pulmonary embolism.

Pathophysiology

DVT classically arises from Virchow's triad: venous stasis, endothelial injury, and hypercoagulability. Stasis (e. g, immobility, heart failure) reduces washout of activated clotting factors; endothelial disruption (trauma, surgery, IV catheters) exposes prothrombotic surfaces; and inherited/acquired thrombophilia (including cancer-associated coagulation activation) amplifies thrombin generation. Fibrin- and red cell-rich clot forms in deep veins (often calf veins, with possible proximal propagation). Acute obstruction causes pain/swelling and inflammatory change; later valve damage and persistent outflow obstruction can cause chronic venous hypertension and post-thrombotic syndrome. See Figure from standard haemostasis/pathology chapters illustrating Virchow's triad and proximal embolisation pathway.

Risk Factors

  • Previous DVT or PE
  • Active cancer (including occult malignancy risk)
  • Age >60 years
  • Obesity
  • Recent major surgery (especially within 12 weeks) or trauma
  • Recent hospital admission or bed rest/immobility
  • Pregnancy and postpartum period (especially first 6 weeks postpartum)
  • Oestrogen-containing contraception or hormone replacement therapy
  • Inherited or acquired thrombophilia (e. g, antiphospholipid syndrome)
  • Acute medical illness/infection, inflammatory disease (e. g, IBD, vasculitis), heart failure
  • Long travel >4 hours
  • Smoking and varicose veins

Clinical Features

Symptoms

  • Unilateral calf or leg pain/tenderness, often cramping or throbbing
  • Unilateral leg swelling or a feeling of tightness/heaviness
  • Symptoms worse on walking or weight-bearing
  • May be subtle or asymptomatic

Signs

  • Calf circumference difference >3 cm (measured 10 cm below tibial tuberosity)
  • Pitting oedema (typically unilateral)
  • Local warmth and erythema
  • Dilated collateral superficial veins (non-varicose)
  • Entire leg swelling in more extensive/proximal thrombosis

Investigations

Two-level DVT Wells score:Score >=2 suggests DVT likely; <=1 suggests DVT unlikely
D-dimer:Negative result in low-probability pathway makes DVT unlikely; positive result requires compression ultrasound
Proximal leg vein compression ultrasonography:Non-compressible proximal vein confirms DVT
Repeat proximal ultrasound (if indicated by pathway):Used when initial scan is negative but clinical suspicion remains (e. g, positive D-dimer/high pre-test concern)
Baseline bloods before/at anticoagulation initiation:FBC, renal and liver function, PT and APTT to guide drug choice/safety; treatment should not be delayed awaiting results
Pregnancy/postpartum suspected DVT pathway:Urgent same-day specialist assessment and objective imaging; LMWH used while diagnosis is being clarified unless contraindicated

Management

Lifestyle Modifications

  • Advise early mobilisation once anticoagulated and clinically stable
  • Maintain hydration and avoid prolonged immobility (travel/workplace prevention advice)
  • Safety-net urgently for chest pain, haemoptysis, breathlessness, syncope, or worsening leg symptoms
  • Address reversible risks: smoking cessation, weight reduction, review oestrogen therapy

Pharmacological Treatment

Direct oral anticoagulants (first-line in many non-pregnant adults)

  • Apixaban 10 mg twice daily for 7 days, then 5 mg twice daily (extended prevention: 2.5 mg twice daily after at least 6 months)
  • Rivaroxaban 15 mg twice daily for 21 days, then 20 mg once daily (extended prevention often 10 mg once daily in selected patients)

Check renal/hepatic function and bleeding risk. Avoid in active major bleeding. DOACs are generally avoided in pregnancy/breastfeeding and usually avoided in antiphospholipid syndrome (especially high-risk triple-positive). Review interacting drugs (strong CYP3A4/P-gp modulators).

Parenteral anticoagulant followed by oral agent

  • Enoxaparin 1 mg/kg twice daily SC or 1.5 mg/kg once daily SC (treatment dosing, adjust in renal impairment)
  • Dalteparin 200 units/kg once daily SC (max 18,000 units daily in many protocols)
  • Then Dabigatran 150 mg twice daily after at least 5 days of parenteral anticoagulation
  • Or Edoxaban 60 mg once daily after at least 5 days of parenteral anticoagulation (30 mg once daily if CrCl 15-50 mL/min, body weight <=60 kg, or certain P-gp inhibitors)

Use when apixaban/rivaroxaban are unsuitable. Dabigatran/edoxaban should not be started without initial parenteral anticoagulation. LMWH is preferred during pregnancy. Dose-adjust for renal impairment.

Vitamin K antagonist regimen

  • Warfarin usually started at 5 mg once daily (individualised), overlapped with therapeutic LMWH for at least 5 days and until INR >=2.0 for at least 24 hours

Target INR usually 2.0-3.0. Requires INR monitoring and counselling about interactions (diet, alcohol, medicines). Contraindicated in pregnancy (teratogenic), but compatible with breastfeeding.

Surgical / Interventional

  • Catheter-directed thrombolysis or pharmacomechanical thrombectomy may be considered for selected extensive iliofemoral DVT with severe symptoms, low bleeding risk, and short symptom duration
  • Inferior vena cava (IVC) filter may be considered if anticoagulation is contraindicated or ineffective, with plan for retrieval when safe

Complications

  • Pulmonary embolism (potentially fatal)
  • Post-thrombotic syndrome (chronic pain, oedema, skin change, venous ulceration)
  • Recurrent DVT/PE
  • Chronic venous insufficiency and reduced quality of life
  • Anticoagulant-related bleeding complications

Prognosis

With prompt anticoagulation, short-term outcomes are usually good, but recurrence and chronic venous morbidity remain important. Recurrence risk is lower after a clearly provoked event than after unprovoked DVT, and highest with persistent risk factors such as active cancer or thrombophilia. Post-thrombotic symptoms can develop within 2 years in a substantial proportion of patients, so follow-up and risk-factor modification matter.

Sources & References

💊BNF Drug References(6)

✅NICE Guidelines(1)

📖Textbook References(20)

  • David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1795)[context]
  • David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1313)[context]
  • David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1809, 1810)[context]
  • David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1431)[context]
  • David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1846)[context]
  • David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1809)[context]
  • Netter F. Netter Atlas of Human Anatomy. A Systems Approach 8ed 2022.pdf(pp. 2294, 2295)[context]
  • _OceanofPDF.com_Netters_Anatomy_-_8th_edition_-_Frank_H_Netter_MD.pdf(pp. 2294, 2295)[context]
  • _OceanofPDF.com_Netters_Anatomy_-_8th_edition_-_Frank_H_Netter_MD.pdf(pp. 2295, 2296)[context]
  • Oxford Handbook of Clinical Diagnosis (Huw Llewelyn, Hock Aun Ang, Keir Lewis etc.) (Z-Library).pdf(pp. 234, 235)[context]
  • [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 578, 579)[context]
  • [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 593, 594)[context]
  • [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 1080, 1081)[context]
  • [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 931)[context]
  • [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 528)[context]
  • [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 356, 357)[context]
  • [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 933)[context]
  • [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 295)[context]
  • [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 521, 522)[context]
  • [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 936)[context]

Sources

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