Deep Vein Thrombosis

Original Editor - Jennifer Self

Top Contributors - Karen Wilson, Kim Jackson, Laura Ritchie, Scott Buxton and Jennifer Self  
Leg veins.png

Clinically Relevant Anatomy

Deep Vein Thrombosis (DVT) is when one or more blood clots form in a deep vein of the body. The most common site for DVT is in the lower limbs.[1] Proximal DVTs of the lower extremity (LE) involve the popliteal and/or thigh veins (femoral vein, external iliac vein, deep vein of the thigh), while distal DVTs encompass those that develop in the calf.

DVTs in the upper extremity (UE) are less common (4-10% of all cases).[2] The deep veins of the upper extremity include the jugular, brachiocephalic, subclavian, and axillary veins proximally and the brachial, ulnar, and radial veins distally. In the upper extremity, the subclavian, jugular and axillary veins are the primary vessels in which DVTs form.[2][3]

Pathological Process

Thrombi develop as a result of hypercoagulation and stasis around venous valve sinuses. The majority of deep vein thrombi start in the calf.[4] These clots are firm and are mostly made up of fibrin and red blood cells[1] (see the image of a DVT here). On autopsy, the majority are attached to venous walls.[1]    

Within 72 hours, an estimated 50% of intraoperative calf DVTs resolve on their own.[4] About 1 in 6 of these extend into the proximal veins of the leg,[4] causing venous obstruction and damage to affected valves. A subset of proximal DVTs become mobile and progress to pulmonary embolism (PE), a potentially fatal condition. The incidence of PE is more common in LE than UE DVTs.[3]   

The following video provides a visual representation of DVT pathology:

Risk Factors

Various risk factors play into the formation of DVTs. In adults, blood clotting disorders are associated with spontaneous formation.[1] Several other clinical factors augment patient risk as well:[1]

Clinical Condition Medical Interventions Environment
  • Acute Infection
  • Cancer
  • Stroke or paralysis
  • Previous VTE*
  • Congestive heart failure
  • Pregnancy or peurperium
  • Dehydration
  • Varicose veins
  • Nephrotic syndrome
  • Rheumatological disease
  • Acute inflammatory bowel disease
  • Hormonal treatment
  • Chemotherapy
  • Birth control pills
  • Recent major surgery
  • Prolonged immobility
  • Long air travel

[*VTE= venous thromboembolism]

The UE has its own set of additional risk factors:[2][3]

  • Intravenous catheters
  • Pacemaker cables
  • Anatomical anomalies (ex. shoulder girdle syndrome, clavicular fractures, Paget–von Schroetter syndrome)

Risk factors more prominent in children include sickle cell disease, severe infection, antiphospholipid syndromes and trauma.[5]

Clinical Presentation

DVT in the right leg with swelling and redness

The clinical presentation of individuals with DVT is inconsistent, as many patients are asymptomatic. Those with symptoms may demonstrate the following features in the affected extremity:[1]

  • Discoloration
  • Pain/discomfort
  • Warmth
  • Swelling
  • Tenderness

Clinical Prediction Rule (CPR): Well's Criteria

Well's Criteria is the most commonly used tool to screen for DVT risk:[1]

Clinical Variable Score
Active cancer (treatment ongoing or within previous 6 months, or palliative) +1
Paralysis, paresis, or recent plaster immobilization of the lower extremities +1
Recently bedridden for > 3 days or major surgery within 4 weeks +1
Localized tenderness along the distribution of the deep venous system (Tenderness along the deep venous system is assessed by firm palpation in the center of the posterior calf, the popliteal space, and along the area of the femoral vein in the anterior thigh and groin) +1
Entire lower extremity swelling +1
Calf swelling > 3 cm when compared with the asymptomatic lower extremity (measured 10cm below the tibial tuberosity) +1
Pitting edema confined to the symptomatic lower extremity +1
Collateral superficial veins (non-varicose) +1
Alternative diagnosis as likely or greater than that of proximal DVT (More common alternative diagnoses include cellulitis, calf strain, Baker Cyst, or postoperative swelling) -2

In the original scale, the total score for all items is tallied and the probability of the patient having a DVT is as follows: 0= low probability, 1-2 points= moderate probability,and ≥ 3 points= high probability.[6] An updated version simplifies the scoring process into two categories: < 2 points= DVT unlikely, ≥ 2 points= DVT likely.[7]

Well's Criteria is a valid tool for assessing DVT risk in outpatient[8][9] and trauma[10] patients. It is less useful for stratifying risk in cancer patients[9] and hospitalized patients as a whole.[11] It cannot be used to screen for UE DVT.[2]

Clinical Tests/Examination

The clinical diagnosis of DVT is unreliable. However, in combination with valid screening tools, clinical examination can justify the need for diagnostic testing.

Observation and Palpation

Pitting edema
Clinical observation and palpation should focus on identifying the signs and symptoms described in the "Clinical Presentation" section of this article.

Homan's Sign

Homan's Sign has been used as an indicator for LE DVT since the 1940s.[12] The test is performed by forcefully dorsiflexing the ankle while the knee is extended. Pain and tenderness in the calf is said to be indicative of LE DVT. Despite its historical use, Homan's sign has no diagnostic value.[12]

Diagnostic Procedures

Diagnostic testing is the only definitive way to confirm DVT.[1]

D-Dimer Testing

D-dimer testing is a simple blood test of fibrin degradation. D-dimer levels are increased by any condition that produces fibrin, one of the primary components of deep vein thrombi. The negative likelihood ratio is higher than 99%. According to Wells and colleagues,[13] the test is best used to rule out DVT in outpatients with a low probability of proximal DVT.

Venous Ultrasound

Venous ultrasound is considered to be the first-choice, diagnostic test for patients who are symptomatic and stratify into the moderate and high probability risk groups for Well's Criteria.[1] The test is a safe, non-invasive and inexpensive. Depending on availability, patient characteristics and the location of the suspected DVT, compression ultrasound, duplex ultrasound or color Doppler imaging may be used.[1] The sensitivity and specificity of compression ultrasonography averages 95% for detection of proximal DVT.[13]



Venography is considered the gold standard test for DVT.[1] The test is rarely used due to its invasive nature and the availability of accurate, non-invasive options (ex. D-dimer and venous ultrasound). The procedure involves an x-ray of the veins (venogram) taken after a special dye is injected into the bone marrow or venous vessels.[13]

Management / Interventions

Primary Prevention

A combination of mechanical and pharmacological measures can be used to prevent DVT. Mechanical prophylaxis involves the use of graduated compression stockings (GCS), intermittent pneumatic compression (IPC) and venous foot pumps to improve blood flow in the deep veins of the leg. Common agents for pharmacological prophylaxis include Warfarin, subcutaneous unfractionated heparin (UFH) and low-molecular-weight heparins (LMWH).[3] DVT prevention is most effective when both methods are used simultaneously.[1] In medical and surgical patients ambulation and exercises involving ankle dorsiflexion are encouraged to further minimize venous stasis.[1]

Medical Treatment


Anticoagulation is the usual treatment for DVT. Patients are generally initiated on a brief course (i.e., less than a week) of heparin treatment.[14] If heparin is contraindicated, fondaparinux (FDX) or direct oral anticoagulants (DOAC) [ex. Xarelto, dabigatran, apixaban] may be used.[1] Acute DVT treatment is followed by a maintenance course (typically 3-6 months) of warfarin or other Vitamin K inhibitor.[1][14] Variations in treatment may exist for patients with delayed removal of an intravenous catheter or an ongoing tumor disease in the case of UE DVT.[2]


Although rarely indicated, thrombolytic therapy is used to treat extensive blood clots.[1] A meta-analysis of randomized controlled trials by the Cochrane Collaboration[15] shows improved outcomes with thrombolysis, though this benefit comes at the increased risk of serious bleeding complications.

Inferior Vena Cava (IVC) Filter

IVC filters may prevent pulmonary embolisation and is an option for patients with an absolute contraindication to anticoagulant treatment.[16] Most newer filters can be removed at a later date, if desired.[1] Complications of this intervention include filter erosion, filter migration and obstruction of the inferior vena cava.[1]

Secondary Prevention

Compression stockings.

Early Mobilization

In conjunction with anti-coagulation, bed rest is commonly prescribed in the immediate days following the diagnosis of LE DVT. This practice is applied with the intent of preventing clot dislodgement and the incidence of PE. The theoretical basis behind this protocol has not been supported by the literature.[17][18] According to a systematic review,[18] early ambulation is associated with fewer incidences of new PE and decreased mortality. As such, early mobilization is instrumental for the prevention of DVT sequelae (see the next section on "Implications for Physical Therapy Practice" for guidelines on safe patient mobilization following known DVT).

Graduated Compression Stockings

To prevent DVT recurrence, the application of graduated compression stockings is recommended "beginning within 1 month of diagnosis of proximal DVT and continuing for a minimum of 1 year after diagnosis".[19]

Implications for Physical Therapy Practice

Physical therapists work with patients at risk for and with diagnosed DVT across the continuum of care. For this reason, the American Physical Therapy Association (APTA) has developed clinical practice guidelines (CPG)[20] to facilitate decision making in the prevention and management of LE DVT in adults. The following table outlines the 5 responsibilities of physical therapists (PTs) with actionable recommendations:

PT Responsibilities Actionable Recommendations
(1) Prevention of VTE
  • Encourage patient mobility and physical activity at the individual and institutional level.
  • Recommend/use mechanical compression for individuals at moderate or high risk for DVT
  • Consult with the physician about medication for individuals at moderate or high risk for DVT
  • Provide education on DVT prevention (leg exercises, ambulation, hydration, etc)
  • Provide education on the risk factors, signs and symptoms, and consequences of DVT
(2) Screening for LE DVT
  • Screen for DVT risk using Well's Criteria or the preferred risk assessment model of the treating institution.
  • Communicate screening results and relevant clinical signs and symptoms to the medical team.
  • Provide education on the importance of seeking medical attention for suspected DVT.
(3) Making prudent decisions regarding safe mobility in conjunction with the health care team
  • Advocate for diagnostic testing and wait the results before mobilizing patients with suspected DVT
  • Screen for fall-risk when a patient is on anticoagulation therapy
  • Engage patients with known DVT in early mobilization. Recommendations for how and when it is safe to mobilize a patient with known DVT depends on patient fall-risk the medical treatment being used:
Medical Treatment Safe Mobilization Guidelines
  1. Verify initiation of anticoagulation and type.
  2. Determine if therapeutic levels of anticoagulation have been achieved.
  3. Mobilize the patient once he/she is in a therapeutic range.*
IVC filter
  1. Verify placement of an IVC filter.
  2. Mobilize the patient once he/she is hemodynamically stable.*
Out of bed ordered for a patient with no anticoagulation therapy or IVC filter
  1. Consult with the medical team regarding mobility vs continued bed rest.
(4) Prevention of long-term consequences of LE DVT
  • Engage patients with known DVT in safe mobilization (review section 3 of this table for details).
  • Recommend/use mechanical compression.
  • Provide education on the risks and benefits of mobilization following DVT.
(5) Patient education & shared decision making
  • Patient education should be given throughout the DVT prevention and management process.
  • Patients should have the autonomy to decide if they want to engage in recommended prevention and treatment measures.

*NOTE: Execution of the above recommendations should be done in line with institution-specific policies. Hillegass et al[20] offer a decision making algorithm that may be helpful in the absence of or as a reference point for updating health care system protocols)

Differential Diagnosis

Below is a non-exhaustive list for the differential diagnosis of calf pain in patients with suspected LE DVT:[21][12]


Presentations Diagnosis and VTE.png
Differential Diagnosis and VTE

This presentation, created by Carleen Jogodka as part of the Evidence In Motion OMPT Fellowship, discusses differential diagnosis for venous thromboembolism.

View the presentation


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