Approach to dvt

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Approach to Deep Vein Thrombosis (DVT)

Anatomy

DVT can occur anywhere in the deep venous system. The proximal veins (popliteal, femoral, common femoral, iliac) carry the highest risk of pulmonary embolism. Distal (calf) veins include the posterior tibial, anterior tibial, and peroneal veins.

Diagram of leg vein anatomy. A three-point ultrasound covers the common femoral, femoral, and popliteal veins. Whole-leg ultrasound adds the saphenous, posterior tibial, peroneal, and gastrocnemius veins. - Rosen's Emergency Medicine

Pathophysiology - Virchow's Triad

Three factors predispose to thrombosis:

Venous stasis - immobility, reduced calf pump, obstruction (e.g., gravid uterus compressing iliac veins)
Endothelial injury - venous trauma, surgery, intravenous catheters
Hypercoagulability - deficiencies of antithrombin III, protein C, protein S; malignancy; antiphospholipid syndrome; OCP use; pregnancy

Risk Factors

Category	Examples
Provoked	Surgery, fracture, immobility, hospitalization, pregnancy/postpartum
Medical illness	Active cancer, heart failure, inflammatory bowel disease
Thrombophilia	Factor V Leiden, prothrombin mutation, antiphospholipid antibody
Patient factors	Prior VTE, age, obesity, OCP/HRT
Upper extremity	Indwelling catheters (>90% of cases), Paget-Schroetter syndrome in young athletes

Note: May-Thurner syndrome (left iliac vein compressed by right iliac artery) explains why left leg DVT is slightly more common.

Clinical Features

Hallmarks are unilateral limb pain and swelling, though these can be subtle and nonspecific. Signs include:

Pitting edema
Erythema and warmth
Tenderness along the deep venous distribution
Dilation of superficial collateral veins
Rarely, a palpable venous cord

Homans' sign (calf pain on dorsiflexion) is neither sensitive nor specific and should not be relied upon.

Fever suggests an alternative diagnosis such as cellulitis. Bilateral DVT occurs in fewer than 10% of cases.

Differential Diagnosis

Venous insufficiency / chronic venous congestion
Cellulitis (concurrent DVT is present in only ~3% of proven cellulitis)
Ruptured Baker cyst
Gastrocnemius muscle tear or Achilles tendon injury
Calf hematoma
Asymmetric edema from heart failure or liver disease
Arterial claudication
Rosen's Emergency Medicine, p. 1196-1197

Step 1: Pre-test Probability - Wells DVT Score

Clinical Feature	Points
Active cancer (ongoing treatment, within 6 months, or palliative)	+1
Paralysis, paresis, or recent plaster immobilization of lower extremity	+1
Recently bedridden ≥3 days or major surgery within 12 weeks	+1
Localized tenderness along the deep venous system	+1
Entire leg swollen	+1
Calf swelling ≥3 cm vs asymptomatic side	+1
Pitting edema confined to symptomatic leg	+1
Collateral (non-varicose) superficial veins	+1
Alternative diagnosis at least as likely	-2

Interpretation:

Score < 2: Low pre-test probability (PTP)
Score ≥ 2: High PTP

In pregnant women, the LEFt score is used instead (1 point each for Left leg, Edema, and First trimester). Score 0-1 = low PTP.

Step 2: Diagnostic Workup

D-dimer

A highly sensitive but non-specific fibrin degradation product assay
Standard cutoff: >500 ng/mL (confirm local lab threshold)
Age-adjusted cutoff for patients >50 years: age × 10 ng/mL (e.g., 80-year-old = 800 ng/mL cutoff) - maintains ~95% sensitivity while reducing unnecessary US
False positives with: pregnancy, malignancy, recent surgery, renal failure, SLE, sickle cell disease, advanced age, Black race
Warfarin use may cause false-negative D-dimer results

Venous Compression Ultrasound (Gold Standard)

Three-point compression US (proximal): common femoral, femoral, and popliteal veins
Whole-leg US: adds tibial, peroneal, and gastrocnemius veins; detects distal DVT but increases false-positive rate
Diagnostic criterion: non-compressibility of the vein under probe pressure, absence of flow, no respiratory augmentation

Other Imaging

MRI venography / CT venography: reserved for suspected pelvic vein DVT (e.g., gynecological malignancy with bilateral leg swelling); venous US is still first-line even when pelvic DVT is suspected
Conventional contrast venography: historical gold standard, now rarely used

Step 3: Diagnostic Algorithm

Diagnostic approach to possible DVT incorporating pre-test probability. - Rosen's Emergency Medicine

In practice:

Low PTP (Wells <2): Send D-dimer first. If negative - DVT excluded. If positive - perform 3-point or whole-leg venous US.
High PTP (Wells ≥2): Go straight to venous US (whole-leg preferred). If US negative + D-dimer negative - DVT excluded. If US negative but D-dimer positive - repeat venous US in 7 days to detect distal clot propagation.
High PTP + positive US: Diagnose and treat DVT.
Rosen's Emergency Medicine, p. 1199-1200

Step 4: Management

Anticoagulation (First-line)

Start anticoagulation immediately at time of confirmed diagnosis (or when high PTP and imaging is delayed).

Agent	Initial Dose	Notes
Rivaroxaban (preferred DOAC)	15 mg BD × 21 days, then 20 mg OD	With food; avoid if CrCl <30
Apixaban (preferred DOAC)	10 mg BD × 7 days, then 5 mg BD	With or without food; avoid if CrCl <30
Enoxaparin (LMWH)	1 mg/kg SC q12h or 1.5 mg/kg q24h	Avoid if CrCl <30
Dalteparin	200 unit/kg daily or 100 unit/kg q12h SC	Avoid if CrCl <30
Fondaparinux	5-10 mg SC once daily	For HIT; avoid if CrCl <30
Unfractionated heparin (UFH)	70-80 U/kg bolus, then 17-18 U/kg/h IV	Use in severe renal impairment, pregnancy, high-bleeding risk (reversible)
Warfarin	Overlap with parenteral agent; titrate to INR 2-3	Requires monitoring; inferior to DOACs

DOACs are first choice - equally effective as warfarin, fewer bleeding events (especially intracranial), no monitoring required.

DOAC contraindications/cautions:

Pregnancy (use LMWH)
Severe renal failure (use UFH)
Liver failure
Antiphospholipid antibody syndrome (use warfarin)
High-risk PE

Duration of Anticoagulation

Scenario	Duration
Provoked DVT (surgery, trauma, transient risk)	3 months
Unprovoked DVT	At least 3 months; consider extended (reassess bleeding vs thrombosis risk)
Active cancer (cancer-associated VTE)	LMWH or DOAC; continue as long as cancer active
Recurrent unprovoked VTE	Long-term anticoagulation

Special Situations

Calf (distal) DVT only:

Anticoagulation may be withheld if no symptoms of propagation and low risk - but requires close surveillance with serial US
If patient is symptomatic or has risk factors for propagation, treat

IVC Filter:

Only if anticoagulation is absolutely contraindicated
Use a retrievable filter; remove when anticoagulation becomes safe

Catheter-directed thrombolysis (CDT) / endovascular therapy:

Considered in extensive iliofemoral DVT to reduce post-thrombotic syndrome (PTS) risk
Does not improve mortality but may reduce long-term morbidity in selected cases
Carries higher bleeding risk - not routine

Compression stockings:

No longer routinely recommended to prevent PTS (trials showed no benefit)
May offer symptom relief; encourage early ambulation post-anticoagulation

Step 5: Assess Bleeding Risk Before Anticoagulation

Absolute contraindications:

Active bleeding into a critical organ or uncontrolled site
Severe bleeding diathesis
Recent/planned high-bleeding-risk surgery
Recent major trauma
Recent intracranial, spinal, or ocular hemorrhage

Relative contraindications:

History of major GI bleeding
Intracranial or spinal tumors
Large AAA with severe hypertension
Stable aortic dissection

Use the VTE-BLEED score to stratify: score <2 = 0.5% risk of major bleeding; score ≥2 = 2.0%.

Reversal Agents

Anticoagulant	Reversal Agent
Heparin (UFH)	Protamine sulfate
Warfarin	FFP, 4-factor PCC, Vitamin K
Dabigatran	Idarucizumab
Rivaroxaban, Apixaban	Andexanet alfa

Complications

Pulmonary embolism - the most feared complication; small emboli cause pleuritic chest pain, large emboli cause hemodynamic collapse
Post-thrombotic syndrome (PTS) - chronic pain, swelling, skin changes, and ulceration; affects up to 50% after proximal DVT. A 2026 systematic review (PMID: 41655785) estimated PTS incidence in Europe at significant levels, reinforcing the need for prompt treatment
Phlegmasia cerulea dolens - massive venous occlusion causing limb ischemia; requires urgent intervention

Upper Extremity DVT - Special Note

90% occur with an indwelling catheter, pacemaker wire, or similar device
Without a device: think Paget-Schroetter syndrome (effort-induced thoracic outlet syndrome in young dominant-arm athletes)
Approach: same principles - US, anticoagulation, consider catheter removal
Rosen's Emergency Medicine, pp. 1196-1202; Bailey & Love's Surgery, 28th Ed., pp. 344-345; Gray's Anatomy for Students

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