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Deep Vein Thrombosis (DVT)

Clinical Subject Page

Deep Vein Thrombosis (DVT)

ICD-10

I82.409

Specialty

Cardiology

Onset

Acute

Reviewed

June 2026

On This Page

Overview

Deep vein thrombosis (DVT) is the formation of a thrombus within the deep venous system, most commonly in the lower extremities, which may obstruct venous blood flow and lead to pulmonary embolism (PE).

Etiology & Risk Factors

  • Etiology for Deep Vein Thrombosis (DVT)

    • Venous stasis
    • Endothelial injury
    • Hypercoagulable states (Virchow’s triad)
    • Recent surgery
    • Trauma
    • Malignancy
    • Pregnancy/postpartum
    • Estrogen therapy (OCP/HRT)
    • Inherited thrombophilia

    Risk Factors for Deep Vein Thrombosis (DVT)

    • Previous Deep Vein Thrombosis (DVT)/PE
    • Prolonged immobilization
    • Hospitalization
    • Active cancer
    • Obesity
    • Older age
    • Smoking
    • Heart failure
    • Stroke with paralysis
    • Long-distance travel

Pathophysiology

    • Deep Vein Thrombosis (DVT)  develops due to Virchow’s triad, which includes three major factors that promote thrombus formation.

      Virchow’s Triad

      1. Hypercoagulability
        • Increased tendency for blood to clot
        • Examples: thrombophilia, pregnancy, oral contraceptive use
      2. Endothelial Damage
        • Injury to the vein wall exposes subendothelial collagen
        • Activates the coagulation cascade and platelet adhesion
        • Causes include trauma and inflammation
      3. Venous Stasis
        • Slow or stagnant venous blood flow
        • Causes include:
          • Prolonged immobilization
          • Hospitalization/bed rest
          • Long flights
          • Varicose veins
          • External compression of veins

      Simple Flow

      Virchow’s triad (Hypercoagulability + Endothelial injury + Venous stasis) → Thrombus forms in deep vein → Venous obstruction → Impaired venous return → Leg swelling, pain, warmth → Risk of pulmonary embolism if clot embolizes

Clinical Presentation

  1. Symptoms

    • Unilateral leg swelling
    • Calf pain or tenderness
    • Leg heaviness
    • Warmth
    • Redness
    • Dilated superficial veins

    Signs

    • Unilateral pitting edema
    • Calf tenderness
    • Increased calf circumference
    • Erythema
    • Warm affected limb

History Taking

  • Key Questions

    • When did the leg swelling begin?
    • Is the swelling unilateral?
    • Recent surgery or hospitalization?
    • Prolonged immobility or long travel?
    • Previous DVT or PE?
    • Active cancer?
    • Pregnancy or postpartum?
    • Use of oral contraceptives or hormone therapy?
    • Chest pain or shortness of breath?

    Red Flags for Deep Vein Thrombosis (DVT)

    • Sudden dyspnea
    • Chest pain
    • Hemoptysis
    • Syncope
    • Massive leg swelling (phlegmasia)

Physical Examination

Inspection

  • Unilateral leg swelling (edema)
  • Redness (erythema)
  • Dilated superficial veins (may be present)

Palpation

  • Warm, tender calf or thigh
  • Calf tenderness along the course of the deep veins
  • Increased calf circumference compared with the opposite leg

Vascular Examination

  • Compare both legs for:
    • Swelling
    • Temperature
    • Tenderness
    • Circumference

Severe Deep Vein Thrombosis (DVT) (Emergency)

  • Marked swelling
  • Cold, cyanotic, pulseless limb suggests phlegmasia cerulea dolens, which requires emergency treatment.

Investigations

  • Laboratory

    • D-dimer
    • CBC
    • Coagulation profile
    • Renal function
    • Thrombophilia testing (selected patients)

    Imaging

    • Compression duplex ultrasonography (first-line test)
    • CT or MR venography (selected cases)

    Additional Tests

    • Wells score for Deep Vein Thrombosis (DVT) probability
    • CT pulmonary angiography if PE is suspected

Diagnosis (Well's Score)

Wells Score · Deep Vein Thrombosis (DVT) Probability

CLINICAL PRE-TEST PROBABILITY TOOL FOR SUSPECTED DVT Used alongside D-dimer and compression ultrasound to guide the diagnostic pathway. Each criterion present scores points; one criterion subtracts points if an alternative diagnosis is at least as likely.
Clinical Criterion Points
Active cancer (treatment ongoing, within 6 months, or palliative) +1
Paralysis, paresis, or recent plaster immobilisation of the lower extremity +1
Recently bedridden ≥3 days, or major surgery within 12 weeks requiring general/regional anaesthesia +1
Localised tenderness along the deep venous system +1
Entire leg swollen +1
Calf swelling ≥3 cm larger than asymptomatic leg (measured 10 cm below tibial tuberosity) +1
Pitting oedema confined to the symptomatic leg +1
Collateral superficial veins (non-varicose) +1
Previously documented DVT +1
Alternative diagnosis at least as likely as DVT (e.g. cellulitis, Baker's cyst, muscle strain) −2
Total Score Sum points
Score Interpretation (2-Level Wells)
≤1
DVT Unlikely
Score ≤1. Prevalence of DVT ~5%. Proceed to D-dimer testing; if negative, DVT effectively excluded without imaging.
Low probability
≥2
DVT Likely
Score ≥2. Prevalence of DVT ~17–28%. Proceed directly to compression ultrasound (do not rely on D-dimer alone).
High probability
3-Tier
Alternative Scoring (Original Wells)
Low ≤0, Moderate 1–2, High ≥3 — original 3-tier system; the simplified 2-level (DVT likely/unlikely) is now more widely used in practice.
Reference system
Suggested Diagnostic Pathway
DVT Unlikely (≤1) — perform D-dimer; if negative, DVT excluded; if positive, proceed to ultrasound
DVT Likely (≥2) — proceed directly to compression ultrasound of the proximal leg veins
Ultrasound negative but high clinical suspicion — consider repeat ultrasound in 1 week or further imaging
Interim anticoagulation — consider while awaiting imaging if high suspicion and no contraindication, per local protocol
Cautions & Limitations
Not validated in pregnancy, suspected pulmonary embolism (separate Wells PE score exists), patients already on anticoagulation, or those with prior DVT in the same leg without clear comparison
D-dimer caveats — can be falsely elevated in pregnancy, malignancy, infection, recent surgery, or older age (reducing specificity)
Clinical gestalt still matters — score is an adjunct to, not a replacement for, clinical judgement
Bilateral symptoms — scoring becomes less reliable; consider alternative diagnoses (e.g. heart failure, renal/hepatic disease)
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Related Topics

Management

General Measures

  • Early ambulation
  • Leg elevation
  • Graduated compression stockings (selected patients)

Anticoagulation

  • Direct oral anticoagulants (Apixaban, Rivaroxaban)
  • Low-molecular-weight heparin (LMWH)
  • Unfractionated heparin
  • Warfarin (selected patients)

Advanced Therapy

  • Catheter-directed thrombolysis (selected extensive DVT)
  • Mechanical thrombectomy
  • Inferior vena cava (IVC) filter (if anticoagulation is contraindicated)

Complications

    • Pulmonary embolism
    • Post-thrombotic syndrome
    • Recurrent Deep Vein Thrombosis (DVT)
    • Chronic venous insufficiency
    • Phlegmasia cerulea dolens

Prognosis

  • Excellent with prompt anticoagulation.
  • Untreated Deep Vein Thrombosis (DVT) significantly increases the risk of pulmonary embolism.
  • Some patients develop chronic post-thrombotic syndrome despite treatment.

Key Points / Clinical Pearls

  • Virchow’s triad is the foundation of Deep Vein Thrombosis (DVT) pathophysiology.
  • Compression duplex ultrasound is the first-line diagnostic test.
  • Assess clinical probability using the Wells score.
  • DOACs are first-line therapy for most patients.
  • Always evaluate for pulmonary embolism in patients with DVT who develop chest pain or dyspnea.
  • Early anticoagulation reduces recurrence and mortality.
  • National Center for Biotechnology Information (NIH). Deep Venous Thrombosis, StatPearls.
  • Kearon C, Akl EA, Ornelas J, et al. Antithrombotic Therapy for VTE Disease: CHEST Guideline and Expert Panel Report. Chest. 2016;149:315-352. PMID: 26867832.
  • Wells PS, Anderson DR, Rodger M, et al. Excluding Pulmonary Embolism at the Bedside Without Diagnostic Imaging: Management of Patients With Suspected Pulmonary Embolism Presenting to the Emergency Department by Using a Simple Clinical Model and D-Dimer. Ann Intern Med. 2001;135:98-107. PMID: 11453709.
  • MedlinePlus, National Library of Medicine (NIH). Deep Vein Thrombosis: Health Topic.
  • Konstantinides SV, Meyer G, Becattini C, et al. 2019 ESC Guidelines for the Diagnosis and Management of Acute Pulmonary Embolism Developed in Collaboration With the European Respiratory Society (ERS). Eur Respir J. 2019;54:1901647. PMID: 31473594.