High-yield overview

Wells Score | D-dimer + Ultrasound | Anticoagulation 3-6 Months

2-3%DVT risk after major ortho surgery WITHOUT prophylaxis

95%Sensitivity of compression ultrasound

3-6moAnticoagulation duration for provoked DVT

10-30%Risk of PE if untreated DVT

WELLS SCORE FOR DVT

Low Probability (0-1)

PatternDVT unlikely

TreatmentD-dimer, if negative stop, if positive ultrasound

Moderate (2)

PatternIntermediate probability

TreatmentD-dimer + ultrasound

High Probability (3+)

PatternDVT likely

TreatmentProceed directly to ultrasound

Critical Must-Knows

Wells score stratifies pretest probability - guides D-dimer use
D-dimer has HIGH sensitivity but LOW specificity - rules OUT if negative + low Wells
Compression ultrasound is gold standard (95% sensitive for proximal DVT)
Proximal DVT (popliteal and above) MUST be treated - high PE risk
Anticoagulate 3 months if provoked (surgery), 3-6 months if unprovoked

Clinical Pearls

"
D-dimer useless if high Wells score - go straight to ultrasound
"
Calf vein DVT (distal) controversial - some treat, some serial ultrasound
"
Postoperative DVT is PROVOKED - lower recurrence risk than unprovoked
"
Rivaroxaban and apixaban do NOT need LMWH lead-in (unlike warfarin)

Clinical Imaging

Imaging Gallery

Ultrasonography showing the regression of deep venous thrombosis. a Ultrasonography (iU-22, Philips) images of the left lower extremity showing extensive deep vein thrombosis at the initial examinatio — Ultrasonography showing the regression of deep venous thrombosis. a Ultrasonography (iU-22, Philips) images of the left lower extremity showing extensCredit: Shimizu K et al. via Thromb J via Open-i (NIH) (Open Access (CC BY))

Duplex ultrasonography performed in right leg. (A) The right common femoral vein (CFV); (B) deep femoral vein (DFV) and superficial femoral vein (SFV); and (C) popliteal vein (PV) is compressed by leg — Duplex ultrasonography performed in right leg. (A) The right common femoral vein (CFV); (B) deep femoral vein (DFV) and superficial femoral vein (SFV)Credit: Go JY et al. via Ann Rehabil Med via Open-i (NIH) (Open Access (CC BY))

Duplex ultrasound scan of right lower limb showing deep vein thrombosis. Duplex scan shows absent blood flow in the right common femoral veins (panel a) and right popliteal vein (panel b), indicating — Duplex ultrasound scan of right lower limb showing deep vein thrombosis. Duplex scan shows absent blood flow in the right common femoral veins (panel Credit: Nasrin S et al. via J Med Case Rep via Open-i (NIH) (Open Access (CC BY))

Ultrasonography revealed subcutaneous edema of the lower limbs, which was more marked in the left limb. No gas formation was observed in either leg and deep vein thrombosis was also not observed. — Ultrasonography revealed subcutaneous edema of the lower limbs, which was more marked in the left limb. No gas formation was observed in either leg anCredit: Zhao GJ et al. via Exp Ther Med via Open-i (NIH) (Open Access (CC BY))

Critical Exam Concepts

Wells Score is NOT Diagnostic

Wells score only estimates probability. You still need D-dimer or imaging to diagnose. High Wells = skip D-dimer, go to ultrasound.

D-dimer has Limited Specificity

Postoperative patients often have elevated D-dimer (trauma, surgery, inflammation). Only useful if LOW Wells AND negative D-dimer = excludes DVT.

Proximal vs Distal DVT

Proximal DVT (popliteal vein and above) MUST be treated - 10-30% PE risk. Distal (calf) DVT - controversial, some treat, some observe with serial ultrasound.

Treatment Duration is Risk-Based

Provoked (surgery): 3 months. Unprovoked: 3-6 months minimum, consider indefinite if high risk. Weigh recurrence risk vs bleeding risk.

Quick Decision Guide

Clinical Scenario	Wells Score	Next Step	If Positive
Post-THA, calf swelling, low suspicion	0-1 (Low)	D-dimer first	If D-dimer negative - stop. If positive - ultrasound
Post-trauma, unilateral leg swelling	2 (Moderate)	D-dimer + ultrasound	Treat if ultrasound positive
Whole leg swelling, prior DVT, active cancer	3+ (High)	Skip D-dimer, go to ultrasound	Anticoagulate immediately if positive
Bilateral leg swelling, no other features	Consider alternative diagnosis	Assess for heart failure, hypoalbuminemia	DVT is usually unilateral

Mnemonic

CAPSBEDWells Score for DVT

C	Cancer active 1 point - treatment within 6 months or palliative
A	Active paralysis/immobilization 1 point - cast, bedridden, paresis of lower limb
P	Prior DVT 1 point - documented previous DVT
S	Swelling entire leg 1 point - whole leg swollen
B	Bedridden greater than 3 days 1 point - or major surgery less than 12 weeks
E	Enlarged calf greater than 3cm 1 point - measured 10cm below tibial tuberosity
D	Differential diagnosis unlikely MINUS 2 points - alternative diagnosis more likely

C	Cancer active 1 point - treatment within 6 months or palliative	S	Swelling entire leg 1 point - whole leg swollen	D	Differential diagnosis unlikely MINUS 2 points - alternative diagnosis more likely
A	Active paralysis/immobilization 1 point - cast, bedridden, paresis of lower limb	B	Bedridden greater than 3 days 1 point - or major surgery less than 12 weeks
P	Prior DVT 1 point - documented previous DVT	E	Enlarged calf greater than 3cm 1 point - measured 10cm below tibial tuberosity

Hook:Remember CAPSBED to calculate Wells score - Cancer, Active immobility, Prior DVT, Swelling, Bedridden, Enlarged calf, and Deduct 2 if alternative diagnosis!

Mnemonic

3-3-IDVT Treatment Duration

3	3 months - Provoked Surgery-related DVT needs only 3 months
3	3-6 months - Unprovoked First unprovoked needs 3-6 months minimum
I	Indefinite - Recurrent/Cancer Recurrent or active cancer = indefinite

3	3 months - Provoked Surgery-related DVT needs only 3 months
3	3-6 months - Unprovoked First unprovoked needs 3-6 months minimum
I	Indefinite - Recurrent/Cancer Recurrent or active cancer = indefinite

Hook:3-3-I: 3 months provoked, 3-6 months unprovoked, Indefinite if recurrent or cancer!

Mnemonic

SEEVirchow's Triad for Thrombosis

S	Stasis Immobility, bed rest, long flights, casts
E	Endothelial injury Surgery, trauma, central lines
E	Excessive hypercoagulability Cancer, thrombophilia, pregnancy, OCP

S	Stasis Immobility, bed rest, long flights, casts
E	Endothelial injury Surgery, trauma, central lines
E	Excessive hypercoagulability Cancer, thrombophilia, pregnancy, OCP

Hook:SEE why DVT occurs: Stasis, Endothelial injury, Excessive clotting!

Overview and Clinical Significance

Why Orthopaedic Surgery is High Risk

Orthopaedic surgery is VERY HIGH RISK for VTE due to: venous stasis (immobility, tourniquet), endothelial injury (surgical trauma), hypercoagulability (inflammatory response). THA and TKA have 40-60% DVT risk WITHOUT prophylaxis.

DVT Epidemiology

Incidence: 1-2 per 1000 population annually
Ortho surgery: 2-3% WITH prophylaxis
Peak: Days 7-14 postoperatively
Location: 80% lower limb, 20% upper limb
Proximal vs distal: 60% proximal, 40% calf only

Consequences of Untreated DVT

Pulmonary embolism: 10-30% risk
Post-thrombotic syndrome: 20-50% at 2 years
Recurrent VTE: 10-30% over 5 years
Chronic venous insufficiency
Death from massive PE: 1-5%

Pathophysiology and Virchow's Triad

Virchow's Triad

DVT results from the interplay of three factors (Virchow's Triad):

1. Venous Stasis:

Immobility from surgery, anesthesia, bed rest
Tourniquet use during surgery
Cast immobilization
Long-haul flights (economy class syndrome)
Paralysis (stroke, spinal cord injury)

2. Endothelial Injury:

Surgical trauma to vessels
Positioning pressure during surgery
Central venous catheters
Previous DVT (vessel damage)
Inflammatory conditions

3. Hypercoagulability:

Surgical stress response (tissue factor release)
Cancer (procoagulant factors)
Inherited thrombophilias (Factor V Leiden, Prothrombin mutation)
Acquired states (pregnancy, OCP, HRT)
Dehydration

Orthopaedic Surgery Risk

Why orthopaedic surgery is highest risk:

Prolonged immobility (pre-op, intra-op, post-op)
Direct vascular trauma (hip, knee surgery)
Cement polymerization (heat, emboli)
Tourniquet ischemia-reperfusion
Inflammatory response activating coagulation

Risk by Procedure (without prophylaxis):

THA: 40-60% DVT, 2-5% PE
TKA: 40-70% DVT, 2-5% PE
Hip fracture surgery: 40-50% DVT
Spine surgery: 15-40% DVT
Arthroscopy: 2-5% DVT

Pathophysiology Exam Point

Orthopaedic surgery involves ALL THREE components of Virchow's triad - stasis (immobility), endothelial injury (surgery), and hypercoagulability (inflammatory response). This is why VTE prophylaxis is mandatory.

Clinical Assessment - Wells Score

Clinical Assessment Alone is Unreliable

Clinical features (pain, swelling, warmth) have LOW specificity - many mimics exist. Wells score improves pretest probability estimation but imaging is required for diagnosis.

Wells Score Calculation

Clinical Feature	Points	Clinical Notes
Active cancer	+1	Treatment within 6 months or palliative
Paralysis or recent immobilization	+1	Plaster cast or bedridden with lower limb paresis
Bedridden greater than 3 days OR major surgery less than 12 weeks	+1	Most ortho patients score this
Tenderness along deep venous system	+1	Palpation of deep veins
Entire leg swollen	+1	Thigh and calf both swollen
Calf swelling greater than 3cm vs other leg	+1	Measure 10cm below tibial tuberosity
Pitting edema (symptomatic leg)	+1	Confined to symptomatic leg
Collateral superficial veins	+1	Non-varicose
Previously documented DVT	+1	Prior confirmed DVT
Alternative diagnosis as likely or more likely	-2	Cellulitis, Baker cyst, muscle strain

Wells Score Interpretation

Score	Probability	DVT Prevalence	Next Step
0-1	Low (unlikely)	5%	D-dimer - if negative, stop; if positive, ultrasound
2	Moderate	17%	D-dimer AND ultrasound
3 or more	High (likely)	53%	Proceed directly to ultrasound (skip D-dimer)

Diagnostic Investigations

DVT Diagnostic Algorithm

Step 1Calculate Wells Score

Use clinical features to calculate Wells score (0-1 Low, 2 Moderate, 3+ High). This determines next step.

Step 2A (if Low)D-dimer

If Wells 0-1 (Low), check D-dimer. If NEGATIVE - DVT excluded (99% NPV). If POSITIVE - proceed to ultrasound.

Step 2B (if High)Skip to Ultrasound

If Wells 3+ (High), D-dimer has low utility - go directly to compression ultrasound. Start empiric anticoagulation if delay expected.

Step 3Compression Ultrasound

Proximal leg vein ultrasound (femoral and popliteal veins). If negative but high suspicion, repeat at 7 days. If positive, treat.

D-dimer Testing

Principle: D-dimer is a fibrin degradation product elevated in VTE. High sensitivity (95-98%) but low specificity (40-60%).

When D-dimer is Useful

Low Wells score (0-1)
Negative D-dimer = DVT excluded
High negative predictive value (99%)
Avoids unnecessary imaging

When D-dimer is NOT Useful

High Wells score (3+) - go to imaging
Postoperative patients - often elevated
Cancer, pregnancy, elderly - often elevated
Positive D-dimer does NOT diagnose DVT

Interpretation:

Negative D-dimer + Low Wells: DVT excluded, no further testing
Positive D-dimer: Proceed to ultrasound (does NOT confirm DVT)
In postop ortho patients: Often falsely elevated - limited utility

The key point is that D-dimer is a rule-out test only, not a diagnostic test.

Ultrasound Imaging

Annotated ultrasound demonstrating deep vein thrombosis of the femoral vein — Compression ultrasound of the femoral vein demonstrating DVT. The thrombus appears as echogenic material within the vein lumen. Labels indicate key anatomical structures and the thrombosed vessel.Credit: Wikimedia Commons. CC BY-SA 4.0

Ultrasound demonstrating non-compressible vein in groin indicating DVT — Compression ultrasound in the groin demonstrating the pathognomonic finding of DVT: non-compressibility of the vein. The arrow marks the thrombosed vessel which fails to collapse with probe pressure, confirming thrombus presence.Credit: Wikimedia Commons. CC BY-SA 4.0

Treatment - Anticoagulation

Management algorithm for Dvt Diagnosis TreatmentCredit: OrthoVellum

Start Anticoagulation Immediately if DVT Confirmed

Once DVT is diagnosed, start anticoagulation immediately (same day). Delays increase PE risk. Choice of anticoagulant depends on patient factors, renal function, and bleeding risk.

Anticoagulant Options for DVT Treatment

Agent	Advantages	Disadvantages	Practice Note
Rivaroxaban/Apixaban (DOACs)	Oral from day 1, no monitoring, no LMWH lead-in	Cost, renal impairment, limited reversal options	Globally first-line for non-cancer VTE
LMWH + Warfarin	Cheap, reversible, familiar	LMWH injections, INR monitoring, drug interactions	Still used where DOAC cost/access is limiting
LMWH alone	No monitoring, safe in cancer	Daily injections, expensive long-term	Cancer-associated VTE (CLOT); DOACs now an option (Caravaggio)
Dabigatran/Edoxaban	Oral, predictable	Need 5-10d LMWH lead-in, renal clearance	Used less than rivaroxaban/apixaban

Direct Oral Anticoagulants (First-Line)

Rivaroxaban:

15mg BD for 21 days, then 20mg daily
No LMWH lead-in needed
Reduce to 15mg daily if CrCl 30-50

Apixaban:

10mg BD for 7 days, then 5mg BD
No LMWH lead-in needed
Reduce to 2.5mg BD if 2 of: age greater than 80, weight less than 60kg, creatinine greater than 133

Advantages: Oral from day 1, predictable, no monitoring, easier than warfarin.

Contraindications: CrCl less than 30, active bleeding, mechanical valve, antiphospholipid syndrome.

Treatment Duration

VTE Type	Duration	Rationale	Recurrence Risk
Provoked (surgery)	3 months	Transient risk factor removed	1-3% annual recurrence
Unprovoked first	3-6 months minimum	Assess bleeding vs recurrence risk	10% first year, 5% annual after
Recurrent unprovoked	Indefinite	High recurrence risk (15% annual)	15% annual if stopped
Active cancer	Indefinite (while cancer active)	Ongoing hypercoagulable state	High recurrence
Thrombophilia (inherited)	Variable, often indefinite	Persistent increased risk	Depends on thrombophilia type

Post-Surgical DVT is Provoked

DVT occurring after orthopaedic surgery is PROVOKED (transient risk factor). Treat for 3 months only. Lower recurrence risk (1-3% annually) vs unprovoked DVT (10% first year). Do NOT automatically anticoagulate indefinitely.

D-dimer to Guide Extended Therapy

In unprovoked DVT, positive D-dimer 1 month after stopping anticoagulation predicts higher recurrence risk. May guide decision for extended anticoagulation.

Special Situations

Calf Vein DVT - Controversial Management

Ultrasound demonstrating thrombosis in the fibular (peroneal) veins of the calf — Axial plane ultrasound showing thrombosis in the fibular (peroneal) veins. Calf vein DVT is more challenging to diagnose by ultrasound (60-70% sensitivity) and its management remains controversial - some centres treat, others perform serial ultrasound to monitor for proximal propagation.Credit: Wikimedia Commons. CC BY-SA 3.0

Two Approaches:

Strategy	Rationale	Recommendation
Anticoagulate for 6 weeks	Prevent propagation (20-30% propagate to proximal veins)	If symptomatic, high risk patients
Serial ultrasound (days 7, 14)	Treat only if propagates to proximal veins	If asymptomatic, low bleeding risk

Current trend: Serial ultrasound unless high-risk features (extensive thrombus, severe symptoms, active cancer, prior VTE).

Complications of DVT and Anticoagulation

DVT Complications

Complication	Incidence	Prevention/Management
Pulmonary embolism	10-30% untreated	Anticoagulation prevents PE
Post-thrombotic syndrome	20-50% at 2 years	Compression stockings (debated), early ambulation
Recurrent VTE	10% first year (unprovoked)	Extended anticoagulation if high risk
Chronic venous insufficiency	Variable	Compression, elevation
Phlegmasia cerulea dolens	Rare	Emergency surgical thrombectomy

Anticoagulation Complications

Complication	Risk	Management
Major bleeding	1-3% annually	Reversal agents, hold anticoagulant
Intracranial hemorrhage	0.5-1% annually	Stop anticoagulation, reversal agent, neurosurgical review
GI bleeding	2-4% annually	Endoscopy, reversal, PPI
Heparin-induced thrombocytopenia	1-5% with UFH	Stop heparin, use alternative (argatroban, fondaparinux)
Warfarin skin necrosis	Rare (Protein C deficient)	Bridge with heparin when initiating warfarin

Phlegmasia Cerulea Dolens

Phlegmasia cerulea dolens is massive iliofemoral DVT causing limb-threatening ischemia. Features: severely swollen, blue, painful leg with absent pulses. Emergency treatment: anticoagulation +/- surgical thrombectomy or catheter-directed thrombolysis. Fasciotomy if compartment syndrome develops.

Controversies and Areas of Uncertainty

Isolated Distal (Calf) DVT

Whether to anticoagulate or perform serial ultrasound remains debated. Trial data (e.g. the CACTUS study) found limited benefit from anticoagulation in low-risk patients, so many guidelines now favour surveillance unless severe symptoms, extensive thrombus, prior VTE, or active cancer are present.

DOACs in Cancer-Associated VTE

LMWH was the historic standard (CLOT), but Caravaggio and Hokusai-VTE Cancer have shifted practice toward oral apixaban or edoxaban. Residual uncertainty centres on GI/GU tumours, where mucosal bleeding risk may favour LMWH or apixaban over edoxaban/rivaroxaban.

Duration After Provoked DVT

Three months is standard for surgery-provoked DVT, but optimal duration when a transient risk factor coexists with a persisting one (e.g. obesity, prior VTE) is not firmly defined and is increasingly individualised using D-dimer and risk scores.

Compression and Catheter-Directed Therapy

Routine graduated compression stockings to prevent post-thrombotic syndrome are no longer recommended after the SOX trial. The role of catheter-directed thrombolysis for extensive iliofemoral DVT (ATTRACT trial) is limited to selected younger patients with severe symptoms.

Evidence Base

Wells Clinical Prediction Rule - Pretest Probability for DVT

Wells PS, Anderson DR, et al. • Lancet (1997)

Key Findings:

Prospective cohort of 593 outpatients with suspected DVT
DVT prevalence rose with clinical score: 3% (low), 17% (moderate), 75% (high)
Structured pretest probability plus proximal ultrasound was safe and feasible
Only 0.6% of those classified as DVT-negative had VTE events over 3 months

Clinical Implication: The Wells model stratifies pretest probability so that low-risk patients can be safely managed with D-dimer and a single ultrasound, reducing serial imaging.

Verify on PubMed (PMID 9428249)

Exam Viva Scenarios

Use these scenarios to practise clinical reasoning and management decisions

CLINICAL SCENARIOStandard

Scenario 1: Post-TKA Suspected DVT (~2-3 min)

CLINICAL PROMPT

"A 65-year-old woman presents 10 days after total knee arthroplasty with new onset left calf pain and swelling. Her right leg (operated) is also swollen but that is unchanged. Wells score is 2 (surgery less than 12 weeks, calf swelling). How would you investigate and manage?"

PRACTICAL APPROACH

This patient has moderate probability DVT based on Wells score of 2. My approach: First, I would complete a thorough history - onset of symptoms, prior VTE, family history, cancer screening. Examination would assess extent of swelling (measure calf circumference 10cm below tibial tuberosity), check for Homans sign (low sensitivity), and look for alternative diagnoses like cellulitis or ruptured Baker cyst. Second, investigations: With Wells score 2 (moderate probability), I would order both D-dimer AND compression ultrasound of the left leg (proximal veins). The D-dimer may be elevated postoperatively due to surgical inflammation, so I would not rely on it alone. The ultrasound is the definitive test - looking for non-compressibility of the femoral and popliteal veins. Third, if ultrasound confirms proximal DVT, I would start anticoagulation immediately. My first choice would be a DOAC (rivaroxaban 15mg BD for 21 days then 20mg daily, or apixaban 10mg BD for 7 days then 5mg BD). No LMWH lead-in is needed with these agents. I would check renal function first - if CrCl less than 30, I would use LMWH + warfarin instead. Fourth, duration of treatment: This is a PROVOKED DVT (post-surgical), so I would treat for 3 months only. Counsel about bleeding risk, need for compliance, and when to return if symptoms worsen.

KEY CLINICAL POINTS

Wells score 2 = moderate probability = D-dimer AND ultrasound

D-dimer often elevated postop - ultrasound is definitive

Start anticoagulation immediately if DVT confirmed

DOACs (rivaroxaban, apixaban) are first-line - no LMWH bridge needed

Provoked DVT = 3 months treatment

COMMON PITFALLS

Relying on D-dimer alone in postoperative patients - often falsely elevated

Not starting anticoagulation immediately if DVT confirmed

Using warfarin without knowing DOACs are first-line now

Anticoagulating for 6-12 months for provoked DVT - 3 months is sufficient

FURTHER QUESTIONS

"What if the ultrasound shows isolated calf vein DVT?"

"What if she has CrCl 25 ml/min?"

"When would you consider indefinite anticoagulation?"

CLINICAL SCENARIOChallenging

Scenario 2: High Wells Score DVT (~2-3 min)

CLINICAL PROMPT

"A 72-year-old man with known metastatic prostate cancer presents with entire left leg swelling and pain. He had a previous DVT 2 years ago. Wells score is 5. What is your diagnostic and management approach?"

PRACTICAL APPROACH

This patient has HIGH probability DVT with Wells score 5 (active cancer +1, prior DVT +1, entire leg swelling +1, bedridden/major surgery +1, no alternative diagnosis +1). My approach: First, with high Wells score, I would skip D-dimer and proceed directly to imaging - compression ultrasound of the entire left leg from common femoral to calf veins. Given the entire leg swelling, I am concerned about iliac vein or IVC involvement, so I may also request CT venography to assess central veins. Second, while awaiting imaging, I would consider starting empiric anticoagulation with LMWH if there will be any delay, given the high pretest probability and his cancer (high VTE risk). Third, if DVT is confirmed, this is CANCER-ASSOCIATED VTE which has specific management: LMWH is preferred over warfarin based on the CLOT trial (lower recurrence with LMWH). I would use enoxaparin 1mg/kg BD or dalteparin. DOACs are emerging alternatives but have higher bleeding risk in some GI/GU cancers. Fourth, duration: Indefinite anticoagulation while cancer is active. This is recurrent VTE in a patient with active malignancy - very high recurrence risk if anticoagulation stopped. Fifth, I would also consider IVC filter if he has contraindication to anticoagulation or recurrent VTE despite adequate anticoagulation.

KEY CLINICAL POINTS

High Wells score (3+) = skip D-dimer, go straight to ultrasound

Entire leg swelling suggests iliac/IVC thrombus - may need CT venography

Cancer-associated VTE = LMWH preferred (CLOT trial)

Anticoagulate indefinitely while cancer active

Consider IVC filter if contraindication to anticoagulation

COMMON PITFALLS

Ordering D-dimer with high Wells score - wastes time, go to imaging

Using warfarin for cancer VTE - LMWH is superior

Stopping anticoagulation at 3-6 months in active cancer - should be indefinite

Missing central vein involvement with leg ultrasound alone

FURTHER QUESTIONS

"What are the indications for IVC filter?"

"How would you manage if he had a major bleed while on LMWH?"

"Would you use a DOAC in this patient?"

CLINICAL SCENARIOChallenging

Scenario 3: Isolated Calf Vein DVT in a Day-Case Patient (~2-3 min)

CLINICAL PROMPT

"A fit 40-year-old man returns 8 days after day-case knee arthroscopy with mild calf discomfort. Ultrasound shows an isolated, non-occlusive thrombus confined to the peroneal (calf) veins, with patent popliteal and femoral veins. He has no prior VTE, no cancer, and no bleeding risk factors. How do you manage him?"

PRACTICAL APPROACH

This is an isolated distal (calf) DVT, which is a recognised area of controversy. First, I would confirm the extent of disease - the thrombus is confined to the calf veins below the popliteal vein, the proximal veins are patent, and he is haemodynamically well with no signs of proximal propagation. Second, I would weigh the two accepted strategies. One option is anticoagulation, typically for around 6 weeks, to prevent propagation, since roughly a fifth of distal DVTs extend proximally. The alternative, supported by trials such as CACTUS which showed limited benefit from anticoagulation in low-risk patients, is serial compression ultrasound at about days 7 and 14 to detect proximal extension, treating only if it propagates. Third, I would individualise: this patient is low risk - no cancer, no prior VTE, low bleeding risk, but he is symptomatic. Given the recent surgery (a transient provoking factor) and that he is reliable for follow-up, I would have a shared discussion. A reasonable plan is a short course of a DOAC if symptoms are troublesome, or serial ultrasound surveillance with early DOAC if propagation occurs. Fourth, if I do anticoagulate, I would use a DOAC for around 6 weeks given this is provoked, and counsel on bleeding, compliance, and red-flag symptoms of PE. Fifth, I would encourage early mobilisation and reassure him that isolated calf DVT has a low PE risk while monitored.

KEY CLINICAL POINTS

Isolated distal (calf) DVT is a genuine controversy - treat OR serial ultrasound

About 20-30% of calf DVTs propagate proximally - that is the rationale for surveillance

Low-risk patients can be safely managed with serial ultrasound (e.g. CACTUS data)

If anticoagulating provoked distal DVT, a short course (around 6 weeks) is reasonable

Shared decision-making and reliable follow-up are essential

COMMON PITFALLS

Treating every calf DVT for 3 months as if it were proximal

Discharging without a surveillance plan if choosing not to anticoagulate

Forgetting that proximal veins must be confirmed patent before calling it isolated distal DVT

Ignoring high-risk features (cancer, prior VTE, extensive thrombus) that would mandate treatment

FURTHER QUESTIONS

"Which patients with calf DVT should always be anticoagulated?"

"How does management change if repeat ultrasound shows popliteal extension?"

"What is the PE risk of an untreated, non-propagating calf DVT?"

MCQ Practice Points

Wells Score Interpretation

Q: A patient has Wells score of 1. What is the next appropriate step? A: D-dimer. Low Wells (0-1) = check D-dimer. If negative, DVT excluded. If positive, proceed to ultrasound.

Proximal vs Distal DVT

Q: What is the main difference in management between proximal and distal DVT? A: Proximal DVT (popliteal and above) MUST be treated due to 10-30% PE risk. Distal (calf) DVT can be managed with serial ultrasound OR anticoagulation depending on symptoms and risk factors.

DOAC Advantages

Q: What is the main advantage of rivaroxaban and apixaban over warfarin for DVT treatment? A: No LMWH lead-in needed. Rivaroxaban and apixaban can be started orally from day 1, whereas warfarin requires 5-10 days of LMWH bridging.

Treatment Duration

Q: How long should a post-surgical (provoked) DVT be anticoagulated? A: 3 months. Provoked VTE has low recurrence risk (1-3% annually) after transient risk factor removed.

Guidelines, Registries & Global Practice

Global Epidemiology

Population incidence of VTE: approximately 1-2 per 1000 adults annually, rising sharply with age (over 5 per 1000 above age 80).
DVT-to-PE ratio: roughly two-thirds of incident VTE presents as DVT alone, one-third as PE with or without DVT.
Surgical attributable risk: without prophylaxis, venographic DVT after major lower-limb arthroplasty reaches 40-60%; symptomatic VTE with modern prophylaxis is approximately 1-3%.
Ethnic variation: VTE incidence is reported lower in East Asian and South Asian populations than in European-ancestry populations, though prophylaxis is still indicated after major orthopaedic surgery.

Side-by-Side Guideline Comparison

Major Society Guidance on DVT Diagnosis and Treatment

Body	First-line treatment	Provoked DVT duration	Compression stockings
ACCP / CHEST (US)	DOAC over VKA for non-cancer VTE (Grade 2B)	3 months	Not routine for preventing PTS (Grade 2B)
NICE NG158 (UK)	Apixaban or rivaroxaban first-line	3 months (3-6 if active cancer)	Not offered solely to prevent PTS
ESC / ISTH (Europe)	DOAC preferred unless contraindicated	3 months for transient provoking factor	Considered for persistent symptoms, not routine
ASH (US, 2020)	DOAC over VKA; DOAC acceptable in many cancers	3 months for surgery-provoked	Suggests against routine use

Where Guidelines Converge

Across ACCP/CHEST, NICE, ESC and ASH the message is consistent: DOACs are first-line for most non-cancer DVT, provoked (surgery-related) DVT is treated for 3 months, and graduated compression stockings are no longer recommended purely to prevent post-thrombotic syndrome. Differences are mostly in emphasis, not direction.

Registry and Surgical-Context Notes

Arthroplasty registries (NJR England/Wales, AOANJRR Australia, AJRR US, Swedish/Norwegian registries) track symptomatic VTE and 90-day readmission as quality metrics rather than venographic endpoints, reflecting the move to clinically relevant outcomes.
Aspirin as extended prophylaxis after hip/knee arthroplasty (following a short DOAC lead-in) is supported by EPCAT II and is increasingly reflected in registry-era practice and AAOS/ICM consensus.

High- vs Limited-Resource Practice Variation

Well-resourced settings: same-day compression ultrasound, age-adjusted D-dimer, and DOAC-based outpatient treatment are standard; many proximal DVTs are managed without admission.
Limited-resource settings: ultrasound access may be delayed, so empirical LMWH while awaiting imaging is more common; warfarin remains widely used where DOAC cost or INR-monitoring infrastructure dictates, and LMWH may be the only practical option for cancer-associated VTE.

DEEP VEIN THROMBOSIS - DIAGNOSIS AND TREATMENT

Clinical summary

Wells Score (CAPSBED)

•Cancer active +1, Paralysis +1, Prior DVT +1
•Swelling entire leg +1, Bedridden greater than 3d/surgery less than 12wks +1
•Enlarged calf greater than 3cm +1, Differential diagnosis unlikely -2
•Score 0-1 Low, 2 Moderate, 3+ High

Diagnostic Algorithm

•Low Wells (0-1): D-dimer - if negative stop, if positive ultrasound
•High Wells (3+): Skip D-dimer, go to ultrasound
•Ultrasound: Non-compressible vein = DVT
•D-dimer: High sensitivity, low specificity (useless if postop)

Treatment - Anticoagulation

•First-line: DOACs (rivaroxaban 15mg BD x21d then 20mg, OR apixaban 10mg BD x7d then 5mg BD)
•No LMWH lead-in with rivaroxaban/apixaban
•Alternative: LMWH + warfarin (5-10d overlap until INR 2-3)
•Cancer VTE: LMWH preferred (CLOT trial)

Duration of Treatment

•Provoked (surgery): 3 months
•Unprovoked first: 3-6 months minimum
•Recurrent unprovoked: Indefinite
•Active cancer: Indefinite while cancer active

Special Situations

•Distal (calf) DVT: Serial ultrasound OR treat (controversial)
•CrCl less than 30: Cannot use DOACs - use LMWH + warfarin
•Proximal DVT MUST be treated (10-30% PE risk)
•IVC filter: Only if anticoagulation contraindicated

Clinical Scenario

Wells Score

Next Step

If Positive

Post-THA, calf swelling, low suspicion

0-1 (Low)

D-dimer first

If D-dimer negative - stop. If positive - ultrasound

Post-trauma, unilateral leg swelling

2 (Moderate)

D-dimer + ultrasound

Treat if ultrasound positive

Whole leg swelling, prior DVT, active cancer

3+ (High)

Skip D-dimer, go to ultrasound

Anticoagulate immediately if positive

Bilateral leg swelling, no other features

Consider alternative diagnosis

Assess for heart failure, hypoalbuminemia

DVT is usually unilateral

Clinical Feature

Points

Clinical Notes

Active cancer

Treatment within 6 months or palliative

Paralysis or recent immobilization

Plaster cast or bedridden with lower limb paresis

Bedridden greater than 3 days OR major surgery less than 12 weeks

Most ortho patients score this

Tenderness along deep venous system

Palpation of deep veins

Entire leg swollen

Thigh and calf both swollen

Calf swelling greater than 3cm vs other leg

Measure 10cm below tibial tuberosity

Pitting edema (symptomatic leg)

Confined to symptomatic leg

Collateral superficial veins

Non-varicose

Previously documented DVT

Prior confirmed DVT

Alternative diagnosis as likely or more likely

-2

Cellulitis, Baker cyst, muscle strain

Score

Probability

DVT Prevalence

Next Step

0-1

Low (unlikely)

D-dimer - if negative, stop; if positive, ultrasound

Moderate

17%

D-dimer AND ultrasound

3 or more

High (likely)

53%

Proceed directly to ultrasound (skip D-dimer)

Ultrasound Imaging

Agent

Advantages

Disadvantages

Practice Note

Rivaroxaban/Apixaban (DOACs)

Oral from day 1, no monitoring, no LMWH lead-in

Cost, renal impairment, limited reversal options

Globally first-line for non-cancer VTE

LMWH + Warfarin

Cheap, reversible, familiar

LMWH injections, INR monitoring, drug interactions

Still used where DOAC cost/access is limiting

LMWH alone

No monitoring, safe in cancer

Daily injections, expensive long-term

Cancer-associated VTE (CLOT); DOACs now an option (Caravaggio)

Dabigatran/Edoxaban

Oral, predictable

Need 5-10d LMWH lead-in, renal clearance

Used less than rivaroxaban/apixaban

VTE Type

Duration

Rationale

Recurrence Risk

Provoked (surgery)

3 months

Transient risk factor removed

1-3% annual recurrence

Unprovoked first

3-6 months minimum

Assess bleeding vs recurrence risk

10% first year, 5% annual after

Recurrent unprovoked

Indefinite

High recurrence risk (15% annual)

15% annual if stopped

Active cancer

Indefinite (while cancer active)

Ongoing hypercoagulable state

High recurrence

Thrombophilia (inherited)

Variable, often indefinite

Persistent increased risk

Depends on thrombophilia type

Strategy

Rationale

Recommendation

Anticoagulate for 6 weeks

Prevent propagation (20-30% propagate to proximal veins)

If symptomatic, high risk patients

Serial ultrasound (days 7, 14)

Treat only if propagates to proximal veins

If asymptomatic, low bleeding risk

Complication

Incidence

Prevention/Management

Pulmonary embolism

10-30% untreated

Anticoagulation prevents PE

Post-thrombotic syndrome

20-50% at 2 years

Compression stockings (debated), early ambulation

Recurrent VTE

10% first year (unprovoked)

Extended anticoagulation if high risk

Chronic venous insufficiency

Variable

Compression, elevation

Phlegmasia cerulea dolens

Rare

Emergency surgical thrombectomy

Complication

Risk

Management

Major bleeding

1-3% annually

Reversal agents, hold anticoagulant

Intracranial hemorrhage

0.5-1% annually

Stop anticoagulation, reversal agent, neurosurgical review

GI bleeding

2-4% annually

Endoscopy, reversal, PPI

Heparin-induced thrombocytopenia

1-5% with UFH

Stop heparin, use alternative (argatroban, fondaparinux)

Warfarin skin necrosis

Rare (Protein C deficient)

Bridge with heparin when initiating warfarin

Wells Clinical Prediction Rule - Pretest Probability for DVT

Wells PS, Anderson DR, et al. • Lancet (1997)

Key Findings:

Prospective cohort of 593 outpatients with suspected DVT
DVT prevalence rose with clinical score: 3% (low), 17% (moderate), 75% (high)
Structured pretest probability plus proximal ultrasound was safe and feasible
Only 0.6% of those classified as DVT-negative had VTE events over 3 months

Clinical Implication: The Wells model stratifies pretest probability so that low-risk patients can be safely managed with D-dimer and a single ultrasound, reducing serial imaging.

Verify on PubMed (PMID 9428249)

Body

First-line treatment

Provoked DVT duration

Compression stockings

ACCP / CHEST (US)

DOAC over VKA for non-cancer VTE (Grade 2B)

3 months

Not routine for preventing PTS (Grade 2B)

NICE NG158 (UK)

Apixaban or rivaroxaban first-line

3 months (3-6 if active cancer)

Not offered solely to prevent PTS

ESC / ISTH (Europe)

DOAC preferred unless contraindicated

3 months for transient provoking factor

Considered for persistent symptoms, not routine

ASH (US, 2020)

DOAC over VKA; DOAC acceptable in many cancers

3 months for surgery-provoked

Suggests against routine use

Condition	Discriminating Features	Key Test
Cellulitis	Spreading erythema, warmth, fever, raised inflammatory markers	Clinical; ultrasound to exclude DVT
Ruptured Baker cyst	Sudden calf pain, popliteal fullness, crescent bruise at ankle	Ultrasound (fluid tracking)
Calf muscle (gastrocnemius) tear	Trauma/exertion history, focal tenderness, bruising	Ultrasound/clinical
Superficial thrombophlebitis	Tender palpable cord over superficial vein, no deep involvement	Ultrasound
Post-thrombotic syndrome	Prior DVT, chronic swelling, skin changes, varicosities	History plus ultrasound
Lymphoedema	Non-pitting, chronic, dorsal foot involvement (positive Stemmer sign)	Clinical
Heart failure / hypoalbuminaemia	Bilateral pitting oedema, raised JVP or low albumin	Echo, bloods

Finding	Interpretation	Sensitivity
Non-compressible vein	DVT present	95% for proximal DVT
Fully compressible vein	No DVT	High negative predictive value
Echogenic material in lumen	Thrombus visualization	Confirmatory if seen
Lack of flow on Doppler	Occlusion	Supportive finding

Modality	Indication	Advantage	Limitation
CT venography	Suspected pelvic/IVC thrombus	Visualizes central veins	Radiation, contrast
MR venography	Pregnancy, contrast allergy	No radiation	Expensive, time-consuming
Venography (gold standard)	Rarely used now	Most accurate	Invasive, contrast, phlebitis risk

Condition	Discriminating Features	Key Test
Cellulitis	Spreading erythema, warmth, fever, raised inflammatory markers	Clinical; ultrasound to exclude DVT
Ruptured Baker cyst	Sudden calf pain, popliteal fullness, crescent bruise at ankle	Ultrasound (fluid tracking)
Calf muscle (gastrocnemius) tear	Trauma/exertion history, focal tenderness, bruising	Ultrasound/clinical
Superficial thrombophlebitis	Tender palpable cord over superficial vein, no deep involvement	Ultrasound
Post-thrombotic syndrome	Prior DVT, chronic swelling, skin changes, varicosities	History plus ultrasound
Lymphoedema	Non-pitting, chronic, dorsal foot involvement (positive Stemmer sign)	Clinical
Heart failure / hypoalbuminaemia	Bilateral pitting oedema, raised JVP or low albumin	Echo, bloods

Finding	Interpretation	Sensitivity
Non-compressible vein	DVT present	95% for proximal DVT
Fully compressible vein	No DVT	High negative predictive value
Echogenic material in lumen	Thrombus visualization	Confirmatory if seen
Lack of flow on Doppler	Occlusion	Supportive finding

Deep Vein Thrombosis

Deep Vein Thrombosis

WELLS SCORE FOR DVT

Critical Must-Knows

Clinical Pearls

Clinical Imaging

Imaging Gallery

Critical Exam Concepts

Wells Score is NOT Diagnostic

D-dimer has Limited Specificity

Proximal vs Distal DVT

Treatment Duration is Risk-Based

Quick Decision Guide

CAPSBEDWells Score for DVT

3-3-IDVT Treatment Duration

SEEVirchow's Triad for Thrombosis

Overview and Clinical Significance

DVT Epidemiology

Consequences of Untreated DVT

Pathophysiology and Virchow's Triad

Virchow's Triad

Orthopaedic Surgery Risk

Clinical Assessment - Wells Score

Clinical Assessment Alone is Unreliable

Wells Score Calculation

Wells Score Interpretation

Alternative Diagnoses (Score MINUS 2)

Differential Diagnosis of the Painful Swollen Leg

Diagnostic Investigations

DVT Diagnostic Algorithm

D-dimer Testing

When D-dimer is Useful

When D-dimer is NOT Useful

Compression Ultrasound (Gold Standard)

Alternative Imaging Modalities

Ultrasound Imaging

Treatment - Anticoagulation

Start Anticoagulation Immediately if DVT Confirmed

Anticoagulant Options for DVT Treatment

Direct Oral Anticoagulants (First-Line)

Warfarin + LMWH Bridging

Warfarin Initiation

Cancer-Associated VTE (Special Case)

Treatment Duration

D-dimer to Guide Extended Therapy

Special Situations

Calf Vein DVT - Controversial Management

Upper Extremity DVT

Recurrent DVT on Anticoagulation

Complications of DVT and Anticoagulation

DVT Complications

Anticoagulation Complications

Controversies and Areas of Uncertainty

Isolated Distal (Calf) DVT

DOACs in Cancer-Associated VTE

Duration After Provoked DVT

Compression and Catheter-Directed Therapy

Evidence Base

Wells Clinical Prediction Rule - Pretest Probability for DVT

EINSTEIN-DVT Trial - Rivaroxaban vs Enoxaparin/VKA

AMPLIFY Trial - Apixaban for Acute VTE

CHEST Guideline - Antithrombotic Therapy for VTE Disease

CLOT Trial - LMWH vs Coumarin in Cancer-Associated VTE

Caravaggio Trial - Apixaban vs Dalteparin in Cancer VTE

EPCAT II Trial - Aspirin vs Rivaroxaban for Extended Prophylaxis

Exam Viva Scenarios

Scenario 1: Post-TKA Suspected DVT (~2-3 min)

Scenario 2: High Wells Score DVT (~2-3 min)

Scenario 3: Isolated Calf Vein DVT in a Day-Case Patient (~2-3 min)

MCQ Practice Points

Guidelines, Registries & Global Practice

Global Epidemiology

Side-by-Side Guideline Comparison

Major Society Guidance on DVT Diagnosis and Treatment

Registry and Surgical-Context Notes

High- vs Limited-Resource Practice Variation

DEEP VEIN THROMBOSIS - DIAGNOSIS AND TREATMENT

Wells Score (CAPSBED)

Diagnostic Algorithm

Treatment - Anticoagulation