Thrombus in the deep venous system, most often lower extremity — risk-stratify with Wells, confirm with duplex US, treat with anticoagulation.
Also known as: DVT, deep vein thrombosis, venous thromboembolism, VTE, lower extremity thrombosis
Overview
Formation of thrombus within the deep venous system, most commonly involving lower extremity veins (popliteal, femoral, iliac). Proximal DVT (popliteal or above) carries the highest risk of pulmonary embolism; distal (calf) DVT is generally lower risk.
Epidemiology
Annual incidence of venous thromboembolism ~1-2 per 1000. Together with PE, VTE is the third most common cardiovascular cause of death. Up to half are provoked by identifiable risk factors; the remainder unprovoked.
Try two board-style Deep Vein Thrombosis questions
Real questions from the FirstPassPA bank, with the full explanation. Pick an answer — no signup, no email.
Question 1CardiovascularMedium
A 55-year-old man presents with unilateral leg swelling 5 days after a long flight. His two-tier Wells deep vein thrombosis (DVT) score is 1 (DVT 'unlikely'). High-sensitivity D-dimer returns at 280 ng/mL (cutoff <500). What is the most appropriate next step?
ACT venography of the lower extremity
BNo further imaging or anticoagulation at this time
CCompression ultrasound of the lower extremity
DEmpiric therapeutic anticoagulation
Reveal answer & full explanation
Correct answer: B — No further imaging or anticoagulation at this time
ACT venography of the lower extremity
BNo further imaging or anticoagulation at this time✓
CCompression ultrasound of the lower extremity
DEmpiric therapeutic anticoagulation
Why No further imaging or anticoagulation at this time is correct
For a non-high-probability Wells deep vein thrombosis (DVT) score, a negative high-sensitivity D-dimer (<500 ng/mL) effectively excludes DVT with high negative predictive value
No further imaging is needed when Wells score is 'unlikely' and D-dimer is negative
Why the others are wrong
CT venography of the lower extremity — is rarely first-line in DVT evaluation
Compression ultrasound of the lower extremity — would be the next step only if Wells score were 'likely' (>=2 in the two-tier model), in which case one proceeds directly to compression ultrasound regardless of D-dimer
Empiric therapeutic anticoagulation — is not justified without imaging confirmation in low/moderate probability patients with a negative D-dimer
Question 2CardiovascularEasy
A 34-year-old woman is 2 weeks postpartum after cesarean delivery and now has unilateral calf swelling. Her recovery has been slow and she has spent most days resting at home. Which of the following is the strongest risk factor for this condition?
AMaternal age older than 30 years
BPostpartum iron-deficiency anemia
CRecent pregnancy with immobility
DEpidural anesthesia at delivery
Reveal answer & full explanation
Correct answer: C — Recent pregnancy with immobility
AMaternal age older than 30 years
BPostpartum iron-deficiency anemia
CRecent pregnancy with immobility✓
DEpidural anesthesia at delivery
Why Recent pregnancy with immobility is correct
Unilateral calf swelling postpartum is suspicious for deep vein thrombosis, and the strongest contributor is the postpartum/cesarean state combined with immobility.
These exposures hit all three arms of Virchow's triad: hypercoagulability of pregnancy, stasis from sedentary recovery, and endothelial injury from surgery.
VTE risk is highest in the first 6 weeks after delivery, so this clustering is decisive.
Why the others are wrong
Maternal age older than 30 years — Advancing maternal age adds only a modest increment to peripartum VTE risk and is nowhere near the effect of the postpartum hypercoagulable state after cesarean.
Postpartum iron-deficiency anemia — Anemia after cesarean delivery causes fatigue and pallor, but it is not one of the recognized drivers of peripartum venous thromboembolism the way recent surgery and immobility are.
Epidural anesthesia at delivery — Neuraxial anesthesia matters for spinal hematoma risk when anticoagulation is started, but it does not itself promote deep vein thrombosis.
🔒 Free preview limit reached
Keep reading — start your free trial
You've read your 2 free diagnosis previews. Create your free account to unlock the full Deep Vein Thrombosis (DVT) outline — plus all 514 diagnoses, 6,500+ board-style questions, flashcards, and an AI tutor. Your 7-day free trial includes everything, and there's no credit card required.
Inherited thrombophilia: Factor V Leiden, prothrombin G20210A, protein C/S/antithrombin deficiency
Antiphospholipid antibody syndrome
Obesity, age >60, smoking
Prior VTE (strongest single risk factor for recurrence)
Central venous catheter, indwelling hardware
Pathophysiology
Stasis in venous valve cusps combined with hypercoagulable state initiates thrombus formation. The thrombus may extend proximally or embolize to the pulmonary circulation. Chronic venous outflow obstruction and valvular damage lead to post-thrombotic syndrome.
Clinical presentation
Symptoms
Unilateral leg swelling and pain (most common)
Calf or thigh discomfort, often worse with walking
Warmth, erythema
Asymptomatic in many cases — first manifestation may be pulmonary embolism
Phlegmasia cerulea dolens (rare, limb-threatening): severe swelling, cyanosis, pain from massive iliofemoral thrombus
Signs / physical exam
Unilateral leg swelling >3 cm calf circumference difference (measured 10 cm below tibial tuberosity)
Pitting edema, palpable cord
Erythema, warmth
Homan sign (calf pain with dorsiflexion) — historical, low sensitivity/specificity
Tachycardia, hypoxia if concurrent PE
Differential diagnosis
Cellulitis — Erythema with sharp borders, fever, leukocytosis; warmth without palpable cord; negative duplex
Ruptured Baker cyst — Sudden calf pain with cyst rupture; ultrasound shows fluid tracking down calf without venous thrombus
Wells DVT score: each +1 for active cancer, paralysis/immobilization, recent surgery, localized tenderness along deep veins, entire leg swelling, calf >3 cm difference, pitting edema, collateral superficial veins, prior DVT; subtract 2 if alternative diagnosis as likely. Score ≥2 = likely; <2 = unlikely. Unlikely + negative D-dimer rules out; likely or positive D-dimer warrants duplex.
Labs
D-dimer — sensitive but nonspecific; useful in low-pretest-probability patients to exclude DVT
CBC, BMP, coagulation studies, hepatic function (drug dosing)
Pregnancy test in women of childbearing age
Selective thrombophilia workup (Factor V Leiden, prothrombin G20210A, protein C/S, antithrombin, antiphospholipid antibodies) — in young unprovoked DVT, recurrent VTE, or strong family history; defer testing until off anticoagulation when possible
Age-appropriate cancer screening for unprovoked VTE — no aggressive occult malignancy workup unless symptoms or signs
Imaging
Compression duplex ultrasound — first-line; sensitivity and specificity >95% for proximal DVT
CT or MR venography for proximal pelvic veins or IVC when duplex limited
Echocardiography and CTPA if PE suspected concurrently
Wells criteria for clinical pretest probability — drives D-dimer vs imaging decision
Diagnostic algorithm
flowchart TD
A[Suspected DVT] --> B[Wells DVT score]
B --> C{Score}
C -->|Unlikely <2| D[D-dimer]
D --> E{D-dimer<br/>elevated?}
E -->|No| F[DVT excluded]
E -->|Yes| G[Compression duplex US]
C -->|Likely ≥2| G
G --> H{Thrombus<br/>identified?}
H -->|No| I[Consider alternate dx<br/>or repeat US in 5-7 days<br/>if high suspicion]
H -->|Yes| J[Anticoagulate: DOAC preferred<br/>LMWH for pregnancy/cancer<br/>Warfarin if specific indication]
J --> K{Provoked vs<br/>unprovoked?}
K -->|Provoked| L[3 months therapy]
K -->|Unprovoked / recurrent /<br/>persistent risk| M[Consider indefinite therapy<br/>based on bleeding risk]
Diagnostic and treatment algorithm for suspected lower extremity DVT.
Treatment
First-line
Anticoagulation — direct oral anticoagulants (DOACs) preferred for most acute VTE in absence of contraindications:
• Apixaban 10 mg PO BID × 7 days then 5 mg BID
• Rivaroxaban 15 mg PO BID × 21 days then 20 mg daily with food
• Edoxaban — requires 5-10 day bridge with parenteral anticoagulation first
• Dabigatran — requires 5-10 day bridge with parenteral anticoagulation first
Low-molecular-weight heparin (enoxaparin 1 mg/kg SC q12h) — preferred in pregnancy, active cancer (especially GI malignancy where DOACs have higher bleeding), severe renal impairment may use IV unfractionated heparin
Warfarin with parenteral bridging (target INR 2-3) — for patients on warfarin already, mechanical heart valves, certain APS, or DOAC intolerance
Duration: 3 months minimum for provoked DVT; indefinite for unprovoked proximal DVT or PE with low bleeding risk, recurrent VTE, or persistent risk factor
Second-line / adjunct
IVC filter — only for acute VTE with absolute contraindication to anticoagulation, or recurrent VTE despite therapeutic anticoagulation; retrievable filters preferred and should be removed when anticoagulation can resume
Catheter-directed thrombolysis or thrombectomy — for limb-threatening iliofemoral DVT (phlegmasia) or selected young patients with extensive proximal DVT to reduce post-thrombotic syndrome
Compression stockings (20-30 mmHg) for symptomatic relief; routine use no longer recommended solely to prevent post-thrombotic syndrome (SOX trial)
Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.