Overview of the treatment of lower extremity deep vein thrombosis (DVT)

INTRODUCTION — 

Deep vein thrombosis (DVT) and acute pulmonary embolism (PE) are two manifestations of venous thromboembolism. The mainstay of therapy for DVT is anticoagulation, provided there is no absolute contraindication or prohibitively high bleeding risk. Thrombolysis or interventional therapy is occasionally needed.

This topic discusses the overview of therapy for proximal and distal lower extremity DVT, risk assessment of thrombotic complications (progressive DVT and pulmonary embolization), bleeding complications with anticoagulation, and whether to initiate anticoagulation. Indications for inferior vena cava (IVC) filters and interventional therapy are also discussed.

The diagnosis of lower extremity DVT and selection of anticoagulant regimens and treatment duration are discussed in detail separately. The treatment of upper extremity DVT is also discussed separately:

●(See "Clinical presentation and diagnosis of the nonpregnant adult with suspected deep vein thrombosis of the lower extremity".)

●(See "Venous thromboembolism: Initiation of anticoagulation".)

●(See "Venous thromboembolism: Anticoagulation after initial management".)

●(See "Selecting adult patients with lower extremity deep venous thrombosis and pulmonary embolism for indefinite anticoagulation".)

●(See "Primary (spontaneous) upper extremity deep vein thrombosis", section on 'Approach to treatment' and "Catheter-related upper extremity venous thrombosis in adults", section on 'Treatment'.)

TERMINOLOGY — 

For the purposes of discussion in this topic, the following terms apply (table 1) [1]:

●Provoked DVT – A provoked DVT is one that is precipitated by a known event (eg, surgery, hospital admission, estrogen). It is now also referred to as DVT associated with an identifiable risk factor(s) (table 2).  

Risk factors can be transient or persistent. Transient risk factors are further categorized as "major" or "minor" according to the magnitude of venous thromboembolism (VTE) risk conferred. The role of risk factors in selecting patients for indefinite anticoagulation is discussed separately. (See "Selecting adult patients with lower extremity deep venous thrombosis and pulmonary embolism for indefinite anticoagulation", section on 'Characterize risk factors'.)

●Unprovoked DVT – An unprovoked DVT is one that occurs in the absence of identifiable risk factors.

●Proximal DVT – A proximal DVT is located in the popliteal, femoral, or iliac veins (figure 1).

●Distal DVT – An isolated distal DVT (also known as isolated calf vein DVT) has no proximal component, is located below the knee, and is confined to the calf veins (peroneal, posterior, anterior tibial, and muscular veins). The popliteal vein is not involved.

●Phases of anticoagulation – Anticoagulant therapy for acute DVT is often divided into three phases.

•The initiation phase (or initial therapy) uses parenteral or higher-dose oral agents to control acutely propagating thrombus and prevent extension or embolization.

•The maintenance phase (also called "treatment" or "long-term" phase) of anticoagulation therapy is administered for a finite period beyond initiation, usually three to six months and occasionally up to 12 months. The goal of this phase is stabilizing the thrombus during recovery while intrinsic thrombolysis takes place.

•The extended phase (indefinite) of anticoagulation therapy is administered beyond the finite period, sometimes indefinitely (eg, without a planned stop date). The goal of this phase is secondary prevention. Extended-phase therapy includes periodic reassessment of the risks and benefits of continuing anticoagulation.

●Direct factor Xa and thrombin inhibitors – Direct factor Xa and thrombin inhibitors have been referred to as direct oral anticoagulants (DOACs), non-vitamin K antagonist oral anticoagulants (NOACs), and less commonly, target-specific oral anticoagulants [2,3]. Throughout this topic, we refer to these agents by their pharmacologic class, direct factor Xa and thrombin inhibitors, consistent with society recommendations [3]. (See "Direct oral anticoagulants (DOACs) and parenteral direct-acting anticoagulants: Dosing and adverse effects".)

PRETREATMENT ASSESSMENT OF BLEEDING RISK — 

In all patients with DVT in whom anticoagulation is indicated, we individualize treatment. While the mainstay of treatment for proximal DVT and some cases of distal DVT is anticoagulation, the most serious adverse effect of anticoagulation is major bleeding, which occurs at an annualized event rate of 1.12 percent in those taking direct factor Xa inhibitors and 1.74 percent in those taking vitamin K antagonists for venous thromboembolism (VTE) [4]. The risk of bleeding is additionally higher in the initial period of treatment (estimated at 2 percent, with a case fatality rate of 11.3 percent), though the benefit of anticoagulation in preventing recurrence and VTE-related death is also highest during this time [5-9].  

In all patients, we identify absolute and relative contraindications to anticoagulation, risk factors for bleeding (table 3), and carefully weigh these with the benefits of anticoagulation (prevention of embolization and thrombus propagation).  

Identify absolute contraindications — Absolute contraindications to anticoagulation include:

●Active major bleeding

●Acute intracranial or spinal hemorrhage

●Major trauma (eg, intraabdominal or intrathoracic injuries related to high-speed motor vehicle collision or gunshot wounds)

●Recent, planned, or emergency high-bleeding-risk surgery/procedure (eg, emergency abdominal aortic aneurysm repair, exploratory laparotomy, craniotomy)

●Severe bleeding diathesis, eg, disseminated intravascular coagulation or decompensated cirrhosis (often presenting with prolonged coagulation times and low platelets, though presentation may vary); especially with diffuse oozing from multiple sites

●Severe thrombocytopenia (eg, platelet counts <25,000/microL) (see "Anticoagulation in individuals with thrombocytopenia")

We do not initiate anticoagulation when an active absolute contraindication to anticoagulation is present. In these cases, an inferior vena cava (IVC) filter is typically placed. (See 'Patients with absolute contraindications to anticoagulation' below.)

Identify additional bleeding risk factors — In addition to absolute contraindications for anticoagulation, we evaluate for relative contraindications to anticoagulation and other risk factors for bleeding [4,10]. Risk factors do not portend the same degree of bleeding risk, will vary with the severity of the risk factor, recency of occurrence, and how effectively previous bleeding was controlled. For example:

●Relative contraindications – Some bleeding risk factors are of sufficient magnitude that they may impact the decision to initiate anticoagulation and must be weighed carefully against the projected benefit of anticoagulant therapy. Relative contraindications include:

•Intracranial or spinal tumors (see "Treatment and prevention of venous thromboembolism in patients with brain tumors", section on 'Therapeutic anticoagulation')

•Recurrent gastrointestinal bleeding (eg, from multiple gastrointestinal telangiectasias)

•Large abdominal aortic aneurysm with concurrent severe hypertension

•Stable aortic dissection

•Recent, planned, or emergent low-bleeding-risk surgery/procedure (eg, cholecystectomy, knee or hip replacement)

●Older age – Older age is a risk factor for bleeding, and bleeding has a higher case-fatality rate in older adults. Age is a factor in deciding on whether to continue anticoagulation into the extended phase. (See "Risks and prevention of bleeding with oral anticoagulants", section on 'Age, race, and sex'.)

●Thrombocytopenia – Non-severe thrombocytopenia is not necessarily a contraindication to anticoagulation (eg, platelet counts >25,000 to 50,000/microL), and many patients with non-severe thrombocytopenia can be treated with therapeutic dose anticoagulation. Recommendations for specific patient groups and platelet counts are discussed separately. (See "Anticoagulation in individuals with thrombocytopenia".)

●History of bleeding – Patients with a history of intracranial hemorrhage (eg, history of successfully ablated aneurysm) may be candidates for anticoagulation, but the decision should be individualized and depends upon the risk of embolic events weighed against the risk of recurrent bleeding. Further details are provided separately. (See "Reversal of anticoagulation in intracranial hemorrhage", section on 'Resumption of anticoagulation' and "Spontaneous intracerebral hemorrhage: Secondary prevention and long-term prognosis", section on 'Anticoagulation'.)

Patients with a recent episode of non-major bleeding (eg, epistaxis or heavy menses) are not generally considered high risk for bleeding, and anticoagulation can usually be administered safely in this population.

●Active cancer – Patients with cancer are at increased risk of bleeding (as well as thrombosis), which does not preclude anticoagulant therapy. Further details are provided separately. (See "Anticoagulation therapy for venous thromboembolism (lower extremity venous thrombosis and pulmonary embolism) in adult patients with malignancy", section on 'Bleeding risk'.)

●Acute ischemic stroke – Anticoagulation initiation and timing in ischemic stroke is discussed separately. (See "Prevention and treatment of venous thromboembolism in patients with acute stroke", section on 'Treatment for VTE'.)

●Comorbidities – Patients with liver failure, kidney failure, and diabetes are at increased risk of bleeding. These and other comorbidities are discussed separately. (See "Risks and prevention of bleeding with oral anticoagulants", section on 'Comorbidities'.)

●Concomitant medications – Concomitant use of antiplatelets and nonsteroidal anti-inflammatory drugs (NSAIDs) with anticoagulants increases bleeding risk in patients with VTE [11,12]. These and other medications are discussed separately. (See "Risks and prevention of bleeding with oral anticoagulants", section on 'Concomitant medications'.)

●Others – Other risk factors include the following:

•Anemia (eg, hemoglobin <10 g/dL [100 g/L])

•Excess alcohol use

•History of poor anticoagulant control

•Reduced functional capacity

•Frequent falls

While we may initiate anticoagulation in patients with relative contraindications or other risk factors, additional precautions may be taken to minimize adverse outcomes. (See 'Managing patients with high bleeding risk' below.)

Bleeding risk factors are also considered in decision-making regarding extended phase (indefinite) anticoagulation following completion of the treatment phase.

Estimate bleeding risk — After identifying contraindications to anticoagulation and bleeding risk factors, we perform a gestalt clinical assessment of bleeding risk with anticoagulation. While bleeding scores and categorization schemes exist, they are poorly validated for informing decisions regarding initiating anticoagulation in patients with VTE. However, some use them to estimate the bleeding risk in candidates for extended phase (indefinite) anticoagulation. (See "Selecting adult patients with lower extremity deep venous thrombosis and pulmonary embolism for indefinite anticoagulation", section on 'Bleeding risk models'.)

To estimate bleeding risk, we assess the number and degree of individual bleeding risk factors, whether the factors are modifiable, and how recently the contraindications or bleeding risk factors were present.  

We then classify patients as those with low bleeding risk, high bleeding risk (including those with relative contraindications), and those with absolute contraindications to anticoagulation, as these will affect treatment decisions:

●Low bleeding risk – Patients with a low bleeding risk (no severe or recent risk factors or contraindications) are initiated on anticoagulation if they have an indication (ie, proximal DVT or distal DVT with high extension risk). (See 'Proximal DVT' below and 'High extension risk and low bleeding risk: Anticoagulation' below.)

●High bleeding risk – We individualize decisions about initiating anticoagulation in patients at high bleeding risk. Generally, patients with proximal DVT and high bleeding risk are anticoagulated; however, bleeding risk may sometimes be sufficient to outweigh the benefit of anticoagulation:

•For example, a patient with a history of diabetes, antiplatelet use, and previous stroke may be considered at high bleeding risk, but we take the nature of each risk factor into account and choose strategies to minimize the risk of bleeding. (See 'Managing patients with high bleeding risk' below.)

•Conversely, the patient who is critically ill, with liver failure, thrombocytopenia, and very recent bleeding into a deep space that may be difficult to control (eg, retroperitoneal bleed), may not meet the strict criteria for an absolute contraindication to anticoagulation; nonetheless, we may consider their bleeding risk as prohibitively high and place an IVC filter instead. (See 'IVC filters' below.)  

For patients with isolated distal DVT, choosing strategies to avoid anticoagulation (ie, surveillance ultrasound) can also be considered. (See 'Distal DVT' below.)

●Absolute contraindication to anticoagulation – In patients with proximal DVT and absolute contraindications to anticoagulation, an IVC filter is typically placed. (See 'Patients with absolute contraindications to anticoagulation' below.)

Some risk categorization schemes have estimated major bleeding risk with respect to number of risk factors and provision of anticoagulation [5]. In such schemes, patients without bleeding risk factors were estimated to have a 1.6 percent risk of major bleeding in the first three months of anticoagulation (with initiation of therapy on either unfractionated or low-molecular-weight heparin, followed by vitamin K antagonist) [13]. Those with one bleeding risk factor were estimated to have a twofold elevated risk of major bleeding (3.2 percent) and those with ≥2 risk factors to have an eightfold elevated risk (12.8 percent). However, this risk scheme does not account for overall lower bleeding risk with direct oral anticoagulants (DOACs), and does not account for variability in the nature, modifiability, or degree of individual risk factors.

VTE-specific bleeding scores are also available (eg, VTE-BLEED and PE-SARD) [6,14]. For example, the VTE-BLEED score evaluates risk of bleeding during stable, long-term anticoagulation and includes variables such as active cancer, anemia, history of bleeding, creatinine clearance, age ≥60 years, and uncontrolled hypertension. A score of ≥2 points is associated with high bleeding risk (average bleed incidence of 13 percent); with 0 to 1.5 points associated with low bleeding risk (2.8 percent). However, VTE-BLEED requires external validation before it can be recommended for bleeding assessment in patients undergoing initial anticoagulation and PE-SARD was derived only in patients with acute pulmonary embolism (PE).

A high bleeding risk score is not a contraindication to anticoagulation, especially since bleeding risk is the interaction of both modifiable and nonmodifiable bleeding risk, changing over time as modifiable factors are addressed. Details regarding the use of scoring systems that estimate the risk of bleeding and bleeding risk assessment in those being considered for indefinite anticoagulation are discussed separately. (See "Risks and prevention of bleeding with oral anticoagulants", section on 'Bleeding risk scores' and "Selecting adult patients with lower extremity deep venous thrombosis and pulmonary embolism for indefinite anticoagulation", section on 'Assessing the risk of bleeding'.)

PROXIMAL DVT

Indications for anticoagulation (most patients) — For most patients with acute proximal DVT, we recommend prompt initiation of anticoagulation, provided there is no absolute contraindication or prohibitively high bleeding risk (algorithm 1). Patients should be anticoagulated regardless of the presence of symptoms. The primary objective of anticoagulation is the prevention of further propagation and complications of DVT such as acute pulmonary embolism (PE), progressive or recurrent DVT, post-thrombotic (postphlebitic) syndrome, and death.

We treat patients who have a diagnosis of DVT made on compression ultrasound (CUS) of the lower extremities. If DVT is found incidentally (usually on computed tomography [CT]), a definitive diagnosis should be sought using CUS before anticoagulation due to the lower sensitivity and specificity of CT. The exception is thrombus located in a vein proximal to the ability of ultrasound to visualize (eg, common iliac, inferior vena cava), where CT is the first-line choice for diagnosis. (See "Clinical presentation and diagnosis of the nonpregnant adult with suspected deep vein thrombosis of the lower extremity", section on 'Diagnostic compression ultrasonography (CUS)'.)

If imaging cannot be performed promptly in a patient with suspected DVT, we consider empiric anticoagulation in some patients with a high pretest probability and low risk of bleeding, before diagnostic confirmation [15]. (See "Venous thromboembolism: Initiation of anticoagulation", section on 'Empiric anticoagulation'.)

●Rationale – While no clinical trials have studied anticoagulation versus no anticoagulation in patients with proximal DVT, we recommend anticoagulation for patients with proximal DVT based on the following:

•Indirect evidence from patients with PE demonstrates a survival benefit with anticoagulation compared with no anticoagulation. The only randomized trial of anticoagulation versus no anticoagulation in patients with PE, with or without DVT, demonstrated a survival benefit (6 versus 26 percent mortality; 1 of 16 patients versus 5 of 19 patients) [16]. While patients with proximal DVT are likely to have a lower risk of mortality compared with PE, it is likely that they will also have a similar relative benefit.

•Indirect evidence from patients with distal DVT shows a reduction in the risk of VTE recurrence in patients who are on anticoagulant therapy compared with no anticoagulant therapy. These data are presented below. (See 'High extension risk and low bleeding risk: Anticoagulation' below.)

The absolute benefit from anticoagulation is likely higher in patients with proximal compared with distal DVT as there is a substantially higher risk of PE from thrombus located in proximal veins compared with distal veins. For example, older studies have reported that over 90 percent of acute PE arise from the proximal veins, and a higher proportion of patients who have proximal compared with distal DVT are subsequently clinically diagnosed with PE (44 versus 0 percent) [17-19].

•Observational evidence shows that VTE recurrence is low in patients with proximal DVT who are treated with anticoagulant therapy. Clinical trials comparing anticoagulation regimens find a 2 to 4 percent risk of recurrent VTE in patients on anticoagulation. (See "Venous thromboembolism: Initiation of anticoagulation".)

Further, a meta-analysis of randomized trials comparing different durations of anticoagulation demonstrated that the risk of recurrent VTE was reduced during the period of anticoagulant use (relative risk [RR] 0.20, 95% CI 0.11-0.38) [20].

The greatest benefit of anticoagulation is realized during the treatment phase, especially the first few days and weeks. As an example, one meta-analysis of 13 prospective cohort studies and 56 randomized clinical trials demonstrated decreased case-fatality rates after completing the initial three months of anticoagulation, compared with during the initial three months (3.6 versus 11.3 percent) [8].

Managing patients with high bleeding risk — For many patients who have proximal DVT and high bleeding risk (including relative contraindications or presence of risk factors for bleeding), but no absolute contraindications for anticoagulation, we initiate anticoagulation with close monitoring and follow-up and reassess if bleeding occurs. (See 'Pretreatment assessment of bleeding risk' above.)

To manage anticoagulation, we take the following steps:

●We evaluate each bleeding risk factor or relative contraindication, including whether the risk is modifiable, and attempt to address the underlying cause. As an example, if a patient is on concomitant antiplatelet therapy or nonsteroidal anti-inflammatory drugs, we consider temporary or permanent discontinuation of these agents if appropriate. As another example, in a patient with a history of gastrointestinal bleeding, we evaluate how recently bleeding occurred and the degree of severity; we also evaluate if definitive endoscopic treatment has been pursued, prior to initiating anticoagulation, and whether acid suppression therapy might mitigate the risk of bleeding.

●We counsel patients on the symptoms and signs of bleeding and obtain more frequent laboratory work and follow-up appointments. The frequency of laboratory work and follow-up depends on the acuity of patient care.

•In the inpatient setting, this may involve at least daily clinical re-evaluation and laboratory work including complete blood count (CBC) and basic metabolic panel (BMP); the latter to monitor kidney function in some cases of anticoagulant use, eg, low molecular weight (LMW) heparin.

•In the ambulatory setting, we tailor assessment based on the patient’s risk profile and choice of anticoagulant medication, such as reassessment of platelet counts, liver or kidney function in patients with baseline impairments, and hemoglobin levels in patients in whom occult bleeding is a concern. Monitoring may vary from every few weeks to every few months and in response to any concerning symptoms. If major bleeding occurs, anticoagulation should be discontinued and an inferior vena cava (IVC) filter may then need to be placed, depending on the estimated risk of thrombosis. (See 'IVC filters' below.)

●In patients for whom we have high concern of bleeding, we may choose to initiate treatment with a short-acting agent such as unfractionated heparin. If bleeding occurs, anticoagulation therapy can be quickly discontinued or reversed, if indicated. When tolerance of anticoagulation is demonstrated, therapy is transitioned to a longer-acting agent, which can be administered in the ambulatory setting. (See "Venous thromboembolism: Initiation of anticoagulation", section on 'Anticipated need for discontinuation or reversal'.)

Presence of high bleeding risk also influences the duration of therapy for DVT, which is discussed in detail separately. (See "Venous thromboembolism: Anticoagulation after initial management", section on 'Duration of treatment phase and transition to extended phase'.)

Anticoagulant agent and duration — For patients without a contraindication or unacceptably high risk for bleeding, anticoagulant therapy should be started immediately as a delay in therapy may increase the risk of potentially life-threatening embolization [21,22].

●Agent selection – Selecting an anticoagulant, dosing for parenteral and oral anticoagulants, and empiric anticoagulation are discussed in detail separately. (See "Venous thromboembolism: Initiation of anticoagulation" and "Venous thromboembolism: Anticoagulation after initial management", section on 'Selection of agent'.)

●Duration of therapy – In general, we treat for a minimum of three months. Further discussion on duration of therapy and indications for indefinite anticoagulation are discussed in detail separately. (See "Venous thromboembolism: Anticoagulation after initial management", section on 'Duration of treatment phase and transition to extended phase' and "Selecting adult patients with lower extremity deep venous thrombosis and pulmonary embolism for indefinite anticoagulation".)

Outpatient therapy — Several randomized trials and meta-analyses suggest that, in most patients, treatment of DVT at home is safe and effective [5,23-37]. The decision to treat in the outpatient setting should be made in the context of the patient's clinical condition, understanding of risks and benefits, and preferences. Initiation of anticoagulant therapy should not be delayed while the decision is being made whether to treat the patient at home.

In one meta-analysis of randomized trials, patients treated at home with LMW heparin were less likely to have recurrent VTE than those treated in the hospital with unfractionated heparin (UFH) or LMW heparin (RR 0.58, 95% CI 0.39-0.86) [34]. Additionally, cost savings is another frequently cited advantage of outpatient treatment, and are estimated to range from $500 to $2500 per patient [30,38-47]. Limitations of these studies include a high percentage of patients receiving some in-hospital care, and some studies evaluated LMW heparin use at home as compared with UFH use in the hospital.

●Outpatient treatment candidates – We carefully select patients when considering outpatient treatment of DVT. Outpatient therapy for DVT can be considered when patients have all of the following features (table 4):

•Hemodynamic stability

•Low risk of bleeding

•No severe kidney function impairment

•Sufficient home support for the administration and surveillance of anticoagulant therapy (eg, access to medications, good living conditions, caregiver support, phone access, understanding and ability to return to the hospital should deterioration occur)

Outpatient therapy is not appropriate in patients with any one of the following [48]:

•Massive DVT (eg, iliofemoral DVT, phlegmasia cerulea dolens) (see "Phlegmasia and venous gangrene")

•Patients for whom interventional therapy (eg, catheter-directed thrombolysis) is being considered (see "Catheter-directed thrombolytic therapy in deep venous thrombosis of the lower extremity: Patient selection and administration")

•Multiple recent or severe risk factors for bleeding on anticoagulant therapy

•Comorbid conditions or other factors that warrant in-hospital care

If concomitant PE is present, criteria for outpatient treatment of PE should be used to select appropriate patients (table 5). (See "Acute pulmonary embolism in adults: Treatment overview and prognosis", section on 'Outpatient anticoagulation'.)

●Outpatient agent options – Selecting an agent for outpatient therapy should be individualized and is dependent upon the risk of bleeding, patient comorbidities, preferences, cost, and convenience. Our preferences are discussed in detail separately. (See "Venous thromboembolism: Initiation of anticoagulation", section on 'General population'.)

Patients with absolute contraindications to anticoagulation — In patients with proximal DVT and absolute contraindications to anticoagulation (eg, active major bleeding, major trauma, hemorrhagic stroke), those with prohibitively high bleeding risk, or recent major bleeding while on anticoagulation, we place a retrievable IVC filter [49]. (See 'IVC filters' below.)

IVC filters are associated with complications including thrombosis, vascular injury due to strut penetration, device fracture, and device migration. Thus, after placement of an IVC filter, we reassess and mitigate any modifiable bleeding risks on an ongoing basis. Once the bleeding risk is mitigated, we initiate anticoagulation, and if successful, administer a conventional course of anticoagulation therapy and remove the filter (commonly about four weeks after initiation of therapy although later removal generally is still feasible) [5]. (See 'Risks' below and "Venous thromboembolism: Anticoagulation after initial management".)

DISTAL DVT — 

The treatment of distal DVT varies among centers and clinicians and poses a therapeutic dilemma [15]. We weigh risk factors for proximal extension (and thereby embolization) against the bleeding risk of anticoagulation to choose between immediate anticoagulation versus surveillance using serial lower extremity compression ultrasound (CUS) and reserving anticoagulation for cases of thrombus propagation (algorithm 2). Patient preference plays a major role in this decision, and the decision is sometimes complicated by the patient’s ability to adhere with follow-up testing.

Many patients (up to 40 percent in some studies) with isolated distal DVT resolve without receiving anticoagulant therapy, while others may experience propagation of thrombosis and embolization [50-52]. Overall, patients with distal DVT are at lower risk of embolization than those with proximal DVT [5,17,18,50-66].

Assess risk of proximal extension

●Features associated with high proximal extension risk – Several factors place patients with distal DVT at risk for proximal extension and embolization and favor initiation of anticoagulant therapy (table 6). This includes patients with:

•Symptoms (other than minor ones, such as mild skin discoloration or mild discomfort) – We consider the presence of symptoms (swelling or edema, pain, warmth) as a significant risk factor for proximal extension and embolization. For most patients with symptoms (other than minor ones) and isolated distal DVT of the lower extremity, we perform therapeutic anticoagulation rather than serial CUS, provided the risk of bleeding is low [5,15,67].

Support for this approach is based upon a presumed higher likelihood of embolization (compared to minimally symptomatic and asymptomatic patients) and the possibility of more rapid symptom improvement with anticoagulation. Natural history studies suggest that when left untreated, approximately 10 to 15 percent of patients with symptomatic isolated distal DVT will develop extension into the proximal veins, most often within the first two weeks after diagnosis [50-52,54-60,63,67].

•Additional risk factors [5,10]

-Thrombus close to the popliteal vein (eg, within 1 to 2 cm) or involving the tibio-peroneal trunk

-Unprovoked DVT (DVT occurring in the absence of identifiable risk factors)

-D-dimer >500 ng/mL

-Extensive thrombosis involving multiple veins (eg, >5 cm in length, >7 mm in diameter) or bilateral disease

-Persistent/irreversible risk factors such as active cancer [68,69] or prolonged immobility (table 1)

-Prior DVT or PE

-Inpatient status

-Coronavirus disease 2019 (COVID-19); especially severe disease

●Features associated with low extension risk – Factors associated with low extension and embolization risk and favoring surveillance with serial ultrasound include patients with most or all of the following characteristics [5,10] (table 6):

•No symptoms (or minor symptoms)

•No risk factors for proximal extension

•Minor thrombosis in the muscular veins

•D-dimer level <500 ng/mL

High extension risk and low bleeding risk: Anticoagulation — In general, we initiate anticoagulation in those with distal DVT, high extension or embolization risk, and low bleeding risk. We additionally take patient preference to avoid repeat imaging (ie, surveillance serial ultrasound) into account when deciding to initiate anticoagulation. Full dose and duration of therapeutic anticoagulation should be administered as in proximal DVT. (See 'Anticoagulant agent and duration' above.)

●Efficacy – Several meta-analyses show anticoagulation reduces clot extension and prevents recurrent VTE in this population [5,15,61,70,71]. In one representative meta-analysis including five studies of patients with symptomatic isolated distal DVT, anticoagulant therapy resulted in a 6 percent absolute reduction in VTE recurrence (3.1 versus 9.1 percent; risk ratio 0.34, 95% CI 0.15-0.77) as well as DVT recurrence (2.0 versus 7.9 percent; risk ratio 0.25, 95% CI 0.10-0.67) [71]. The study did not detect a significant difference in major bleeding (0.6 versus 0.8 percent; risk ratio 0.76, 95% CI 0.13-4.62), reduction of pulmonary embolism (1.0 versus 1.2 percent; risk ratio 0.81, 95% CI 0.18-3.59), or in mortality, but the overall risk of these events was low.

While trials evaluating additional risk factors for extension have not been conducted, the benefits of anticoagulation are thought to extend to those patient groups.  

●Duration – Shorter periods of treatment phase anticoagulation have been evaluated, but anticoagulation for 12 weeks compared with 6 weeks reduced recurrences of DVT in a randomized trial (absolute risk 11 versus 19 percent; RR 0.59, 95% CI 0.36-0.95) [65]. (See "Venous thromboembolism: Anticoagulation after initial management", section on 'Duration of treatment phase and transition to extended phase'.)

High extension risk and high bleeding risk: Serial ultrasound — In patients with distal DVT, with high extension risk and high bleeding risk (or contraindications to anticoagulation) (table 3), we favor surveillance with serial compressive ultrasound, although there are limited data to guide the best therapy in this population and individualized consideration of extension and bleeding risk factors is necessary. We additionally take patient preference to avoid bleeding with anticoagulation into consideration. (See 'Pretreatment assessment of bleeding risk' above and 'Serial compressive ultrasound protocol' below.)

Low risk of extension: Serial ultrasound — Patients with isolated distal DVT and no symptoms, or only minor symptoms, and features that support a low risk of embolization can be managed with serial ultrasounds. We suggest surveillance for two weeks with serial lower extremity CUS to assess for proximal thrombus extension.

Support for this approach is derived from several retrospective and prospective observational studies, which have reported that limited thrombosis confined to the muscular veins has a low risk of extension without therapy compared with extensive thrombosis of multiple calf veins (approximately 3 versus 15 percent) [5,50,51,54,55,58,59,67]. In addition, natural history studies suggest that if extension does not occur within two weeks of diagnosis, it is unlikely to occur [50-52,54-60].

Serial compressive ultrasound protocol — We survey patients for thrombus extension or resolution with proximal CUS once a week for two weeks, or earlier if patients develop worsening or new symptoms [15].

For surveillance, we prefer proximal rather than whole-leg CUS because it is sufficient for the detection of proximal DVT where the indication for anticoagulation is strong. However, some institutional protocols may mandate whole-leg CUS. (See "Clinical presentation and diagnosis of the nonpregnant adult with suspected deep vein thrombosis of the lower extremity", section on 'Diagnostic compression ultrasonography (CUS)'.)

Managing based on ultrasound results — Based on the results of CUS, we take the following actions:

●If thrombus fully or partially resolves, or remains unchanged through two weeks of surveillance, no anticoagulation is required. Serial CUS may be discontinued unless new symptoms arise.  

●If thrombus extends into the proximal veins, patients should be anticoagulated or treated with an inferior vena cava (IVC) filter if an absolute contraindication to anticoagulation exists. (See 'Proximal DVT' above and 'IVC filters' below.)

●If thrombus extends toward the proximal veins (eg, within 1 to 2 cm) but remains confined to the calf, we suggest anticoagulation rather than continued surveillance with CUS, as long as bleeding risk is deemed to be acceptable. If bleeding risk is not acceptable, individual risk and benefit assessment is needed as to whether continued surveillance versus placement of IVC filter is appropriate. (See 'Indications for anticoagulation (most patients)' above.)

IVC FILTERS — 

We do not routinely insert inferior vena cava (IVC) filters as stand-alone or adjunctive therapy. However, for patients who have absolute contraindications to anticoagulation, or experience major bleeding while on anticoagulation, an IVC filter may be inserted as a temporary measure while attempts are made to mitigate bleeding risk. The purpose of IVC filters is reduction of pulmonary embolism (PE) risk. (See 'Patients with absolute contraindications to anticoagulation' above.)

Indications — The following are patient populations in which we utilize IVC filter placement:

●Patients with acute proximal DVT and an absolute contraindication to anticoagulation – Absolute contraindications include active major bleeding, major trauma, hemorrhagic stroke, and recent major bleeding while on anticoagulation. While there are limited data, the risk of PE is substantial without treatment. Observational evidence suggests that the risk of PE is low (2 to 4 percent) after IVC placement in patients with a contraindication to anticoagulation [49].  

However, IVC filter placement increases the risk of recurrent DVT and thrombosis at the filter insertion site. Thus, after placement of IVC filter, reassessment and management of the bleeding risk should be conducted on an ongoing basis. Once the bleeding risk is mitigated, we typically initiate anticoagulation, and if successful, administer a conventional course of anticoagulation therapy. We remove the filter once it is clear that anticoagulant therapy is tolerated (commonly about four weeks after initiation of therapy) [5]. (See 'Procedural considerations and ongoing management' below.)

●Patients with isolated distal DVT, who show progression during surveillance and absolute contraindication to anticoagulation – The efficacy of IVC filter placement in patients with symptomatic isolated distal DVT is unknown and not generally performed unless the thrombus shows signs of progression during surveillance and an absolute contraindication to anticoagulation exists. (See 'Low risk of extension: Serial ultrasound' above.)

●Patients with recurrent DVT or PE despite adequate anticoagulation – In rare patients with recurrent DVT or PE despite adequate anticoagulation, we evaluate for etiologies for recurrence, and if these are absent or cannot be mitigated, we place an IVC filter as an adjunct to anticoagulation for further PE prevention [15]. This includes patients in whom an additional embolic event would be poorly tolerated (eg, those with poor cardiopulmonary reserve from massive PE or underlying cardiopulmonary disease, or hemodynamically unstable patients).

Otherwise, we generally do not use IVC filters as a primary treatment or as an adjunct to anticoagulation. Two randomized studies examined the role of IVC filters as an adjunct to anticoagulation in patients with proximal DVT.

●In PREPIC1, 400 patients with proximal DVT were assigned to anticoagulation alone, or anticoagulation plus insertion of a permanent IVC filter [72]. Fewer patients in the IVC filter group developed a PE (1 versus 5 percent) in the first 12 days after randomization, and at two-year follow-up, though this was not significant (3 versus 6 percent, odds ratio [OR] 0.50, 95% CI 0.19-1.33).

●In PREPIC2, 399 patients with PE associated with lower-limb DVT were assigned to anticoagulation alone or anticoagulation plus temporary insertion of a retrievable IVC filter, with retrieval attempted at three months [73]. No difference was detected in rates of recurrent PE in the IVC filter group versus the control group (3 versus 1.5 percent, RR 2.0, 95% CI 0.51-7.89) at three or six months.

No difference in mortality was detected between patients treated with anticoagulation alone and anticoagulation plus IVC filter in PREPIC1 or PREPIC2, though there were few deaths in each study, which may lead to under-detection of a significant difference [72,73].

Risks — IVC filters may decrease the risk of PE in the short-term but at the expense of increased risk of DVT and other complications, including:

●Recurrent DVT and thrombosis at the filter insertion site – As an example, in PREPIC1, patients who received an IVC filter had a higher rate of DVT at two-year follow-up (21 versus 12 percent) and at eight-year follow-up (35 versus 28 percent). In PREPIC2, no difference was detected in recurrent DVT rates at three or six months, which may be related to the retrievable filter and study design. However, in a large, real-world retrospective observational cohort study of nearly 271,000 patients, retrieval rates still remained overall low, with a cumulative incidence of only 15.3 percent at 1.2 years and 16.8 percent at nine years [74].

●Procedural complications including guidewire entrapment, local hemorrhage, fracture, embolization.

●Device-related complications including strut penetration, device migration, and device fracture.

●Post-thrombotic syndrome.

These are discussed in detail separately. (See "Placement of vena cava filters and their complications", section on 'Complications'.)

Procedural considerations and ongoing management — We evaluate the following when deciding to place an IVC filter:

●The thrombus must be located such that the filter will provide a beneficial effect. For example, most IVC filters are placed in the infrarenal portion of the IVC. This position will reduce the risk of embolization of lower extremity thrombus, but will not be of prophylactic value for thrombus located in the renal veins, the upper extremity veins, or intracardiac thrombus.

●Most manufactured filters are now retrievable, and timely retrieval of filters should be undertaken when PE prevention is no longer needed. In general, there has been an overall decline in rates of IVC filter placement and an increase in IVC filter retrieval rates, although retrieval rates still remain suboptimal at many centers [75]. To minimize long-term complications, early consideration of filter retrieval, communication with the inserting proceduralist, and a reliable system to assure follow-up and reassessment for IVC filter retrieval is optimal. At the least, communication from the clinician ordering the procedure (or discharging the patient from the hospital) to the patient and/or primary care provider, to consider retrieval when appropriate, is needed. Some health care systems have developed surveillance and reminder systems that include both interventional radiology and the clinicians managing anticoagulant therapy to ensure that assessment for filter retrieval reliably takes place.

The placement and complications of IVC filters are discussed separately. (See "Placement of vena cava filters and their complications".)

THROMBOLYTIC THERAPY AND THROMBECTOMY — 

For most patients with acute lower extremity DVT, anticoagulant therapy alone is sufficient. Routine use of thrombolytic therapy (systemic and catheter-directed) and/or thrombectomy (surgical or catheter-directed) is not indicated. The principal benefit of such therapy is more rapid relief of symptoms. Long-term outcomes are broadly similar to treatment with anticoagulation alone [76].

●Thrombolysis (usually catheter-directed) is usually reserved for patients with phlegmasia cerulea dolens or massive iliofemoral DVT, or for patients who fail therapeutic anticoagulation. Further details are provided separately. (See "Catheter-directed thrombolytic therapy in deep venous thrombosis of the lower extremity: Patient selection and administration".)

●Thrombectomy can be performed via a catheter (eg, suction thrombectomy) or by open surgery. It may be the only option in patients who are not suitable candidates for or fail thrombolysis. (See "Catheter-directed thrombolytic therapy in deep venous thrombosis of the lower extremity: Patient selection and administration", section on 'Patients at high risk of bleeding or contraindications to thrombolysis' and "Catheter-directed thrombolytic therapy in deep venous thrombosis of the lower extremity: Patient selection and administration", section on 'Patients who fail thrombolysis'.)

Choosing among these options is often at the discretion of the clinician and dependent upon local expertise and clinical factors, such as contraindications and comorbidities.

SPECIAL POPULATIONS — 

Special populations of patients with acute DVT require specific consideration (table 7) and are mostly discussed in the linked sections below.

Heparin-induced thrombocytopenia — For patients with DVT and a diagnosis of heparin-induced thrombocytopenia (HIT), all forms of heparin should be discontinued. This includes unfractionated heparin, low molecular weight heparin, heparin flushes, heparin-bonded catheters, and heparin-containing medications. Immediate anticoagulation with a nonheparin anticoagulant (eg, argatroban, bivalirudin, danaparoid, fondaparinux) is indicated unless there is an absolute contraindication to anticoagulation. The diagnosis and management of patients with HIT are discussed in detail separately. (See "Clinical presentation and diagnosis of heparin-induced thrombocytopenia" and "Management of heparin-induced thrombocytopenia".)

Inherited thrombophilias — In most cases, the presence of an inherited thrombophilia does not change the choice of an anticoagulant or initiation of anticoagulation, but there are considerations in which thrombophilia may affect management (eg, possible avoidance of warfarin in protein C deficiency, or need for antithrombin [AT] administration in some individuals with AT deficiency). Details are presented in separate topic reviews:

●Factor V Leiden – (See "Factor V Leiden and activated protein C resistance", section on 'Patients with VTE'.)

●Prothrombin G20210A mutation – (See "Prothrombin G20210A", section on 'Patients with VTE'.)

●Protein C deficiency – (See "Protein C deficiency", section on 'Thromboembolism management'.)

●Protein S deficiency – (See "Protein S deficiency", section on 'Patients with VTE'.)

●Antithrombin deficiency – (See "Antithrombin deficiency", section on 'VTE treatment (hereditary deficiency)'.)

Patients with malignancy — The approaches to management of VTE in patients with malignancy (“cancer-associated thrombosis”) and specifically patients with brain tumors are discussed in separate topics:

●(See "Anticoagulation therapy for venous thromboembolism (lower extremity venous thrombosis and pulmonary embolism) in adult patients with malignancy".)

●(See "Treatment and prevention of venous thromboembolism in patients with brain tumors".)

Other patient populations

●Antiphospholipid syndrome – (See "Antiphospholipid syndrome: Management".)

●Pregnancy – (See "Venous thromboembolism in pregnancy and postpartum: Treatment" and "Anticoagulation during pregnancy and postpartum: Agent selection and dosing".)

●Children – (See "Venous thrombosis and thromboembolism (VTE) in children: Risk factors, clinical manifestations, and diagnosis" and "Venous thrombosis and thromboembolism (VTE) in children: Treatment, prevention, and outcome".)

●May-Thurner syndrome – (See "May-Thurner syndrome".)

●Phlegmasia cerulea dolens – (See 'Thrombolytic therapy and thrombectomy' above and "Catheter-directed thrombolytic therapy in deep venous thrombosis of the lower extremity: Patient selection and administration" and "Phlegmasia and venous gangrene".)

SUPPORTIVE THERAPIES — 

Additional considerations for patients diagnosed with acute DVT of the lower extremity include ambulation and graduated compression stockings (GCS) for the prevention of post-thrombotic (postphlebitic) syndrome (PTS).

Ambulation — In patients with acute DVT we encourage early ambulation as soon as feasible, in addition to therapeutic anticoagulation as indicated. Patients with severe symptoms of DVT or phlegmasia cerulea dolens may be functionally limited by pain or edema, and ambulation may need to be deferred until symptoms improve. When symptoms such as pain or leg edema limit ambulation, GCS may be useful for symptomatic relief to facilitate ambulation.

This approach is supported by several small randomized trials and meta-analyses that have shown that early ambulation does not increase the risk of recurrent or fatal pulmonary embolism (PE) [23,24,77-86]. Early mobilization may also improve quality of life and reduce pain [86]. Long-term exercise may also reduce the severity of PTS [86]. (See "Post-thrombotic (postphlebitic) syndrome in adults", section on 'Risk factors'.)

The risk of PE during more aggressive forms of exercise, physical therapy, or rehabilitation is unknown. We typically gradually increase exercise training as tolerated by the patient.

Graduated compression stockings — We do not routinely use GCS (providing decreasing pressure from the ankle up the leg, ie, graduated pressure) to prevent PTS, as was traditionally done. Randomized studies have not shown clear, consistent benefit from GCS in preventing PTS [87]. Although GCS are rarely harmful, many patients also decline their use because they are uncomfortable, costly, inconvenient, and may require a caregiver for their application [88].

However, a subset of patients with recurrent DVT or moderate to severe symptoms may consider the potential benefits of GCS to outweigh these inconveniences. In such patients, the purpose of GCS is often focused on symptom reduction rather than PTS prevention. If the decision is made to use GCS, we initiate them after anticoagulant therapy, within two weeks of an acute diagnosis, and continue their use for two years. While studies generally evaluated daily use for approximately two years, many patients discontinue use after shorter periods [88].

Stockings are available in various pressures, usually expressed by the maximum level of pressure provided at the ankle (eg, 20 to 30 or 30 to 40 mmHg) and are produced in various lengths (eg, below the knee, thigh-high). There is no compelling evidence to choose a specific pressure or length, and these are best adjusted to address the symptoms of each patient.

Stockings should be replaced approximately every six months, when the degree of compression begins to wane, although this time varies due to several factors including stocking manufacturer and frequency of laundering. Stockings may require refitting once local swelling is reduced. Alternative approaches of compression bandages or application of GCS for limited periods (eg, for the duration of anticoagulation) or following thrombolytic therapy have not been adequately evaluated.

Contraindications to GCS include skin ulceration, severe arterial insufficiency, allergy to stocking material, and inability to apply stockings.

Evidence evaluating elastic GCS for the prevention of PTS is somewhat conflicting, with smaller trials suggesting possible benefit and one large randomized trial reporting no benefit [5,45,87,89-99]. A meta-analysis of these five randomized trials reported a clinically, but not statistically, significant reduction in the incidence of PTS with elastic GCS (248 versus 400 per 1000 participants, risk ratio 0.62, 95% CI 0.38-1.01) [87]. Most trials were small, used heterogenous outcome measures and/or had some risk of bias. The largest trial was well-conducted and included 806 patients with first proximal DVT. This study found no difference in the rate of PTS with GCS as measured by the less stringent Ginsberg criteria (leg pain and swelling one month or more; 14 versus 13 percent) [97]. A similar lack of benefit was reported when the more rigorous Villalta criteria were applied. Based upon this study, we do not routinely apply GCS for the prevention of PTS.

The use of compression stockings as a therapy for PTS is discussed separately. (See "Post-thrombotic (postphlebitic) syndrome in adults", section on 'Management'.)

MONITORING AND FOLLOW-UP — 

We monitor patients for the complications of both DVT and anticoagulation.

Complications of DVT include further thrombus extension, recurrence, embolization, and post-thrombotic syndrome. To this end, we monitor clinically for symptoms. We do not routinely follow-up with lower extremity compression ultrasound (CUS) following anticoagulant therapy, unless the patient has symptoms or signs of recurrent or persistent DVT, although this practice varies among clinicians.

Although practice varies, we often perform CUS of the affected extremity if the decision is made to discontinue anticoagulation; this serves as a basis for comparison in the event that future DVT is suspected in the same leg.

Details regarding clinical suspicion for recurrence, pulmonary embolism, and the implications of detecting residual vein obstruction after therapy are discussed separately.

●(See "Clinical presentation and diagnosis of the nonpregnant adult with suspected deep vein thrombosis of the lower extremity", section on 'Patients with a history of DVT'.)

●(See "Clinical presentation and diagnostic evaluation of the nonpregnant adult with suspected acute pulmonary embolism".)

●(See "Selecting adult patients with lower extremity deep venous thrombosis and pulmonary embolism for indefinite anticoagulation", section on 'Less well-validated risk factors'.)

We also monitor for anticoagulation-related adverse effects (eg, bleeding, thrombocytopenia) and for the development of conditions that affect the half-life of or contraindications for the anticoagulant used (eg, kidney failure, severe liver disease, pregnancy, weight gain/loss). Further details regarding monitoring patients on anticoagulant therapy are discussed separately.

●(See "Direct oral anticoagulants (DOACs) and parenteral direct-acting anticoagulants: Dosing and adverse effects".)

●(See "Heparin and LMW heparin: Dosing and adverse effects", section on 'Laboratory monitoring/measurement (LMW heparins)'.)

●(See "Clinical use of coagulation tests", section on 'Anticoagulant monitoring'.)

●(See "Venous thromboembolism: Anticoagulation after initial management", section on 'Monitoring'.)

EVALUATING FOR AN UNDERLYING CAUSE — 

Evaluating patients with DVT for an underlying inheritable or acquired risk factor is discussed separately. (See "Evaluating adult patients with established venous thromboembolism for acquired and inherited risk factors".)

SOCIETY GUIDELINE LINKS — 

Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Superficial vein thrombosis, deep vein thrombosis, and pulmonary embolism".)

INFORMATION FOR PATIENTS — 

UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Deep vein thrombosis (blood clot in the leg) (The Basics)")

●Beyond the Basics topics (see "Patient education: Deep vein thrombosis (DVT) (Beyond the Basics)" and "Patient education: Warfarin (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Definitions – Proximal deep vein thrombosis (DVT) is one that is located in the popliteal, femoral, or iliac veins (figure 1).

Distal DVT is confined to the calf veins (peroneal, posterior, anterior tibial, or muscular veins). (See 'Terminology' above.)

●Proximal DVT – Most pulmonary emboli (PEs) originate from proximal DVT (figure 1). Treatment is based on the presence of contraindications and bleeding risk (algorithm 1):

•Most patients – For most patients with acute proximal lower extremity DVT without absolute contraindications to anticoagulation, we recommend immediate anticoagulation (Grade 1B) (algorithm 1). Patients with proximal DVT are at high risk for PE; anticoagulation reduces mortality in PE. (See 'Indications for anticoagulation (most patients)' above.)

•Absolute contraindications to anticoagulation – For patients with acute proximal lower extremity DVT and absolute contraindications to anticoagulation, we recommend prompt retrievable inferior vena cava (IVC) filter placement (Grade 1C). IVC filters likely reduce the risk of PE but increase the risk of recurrent DVT. Anticoagulation should be administered once the contraindication resolves. The filter should be retrieved when the patient is no longer at high risk for PE. (See 'IVC filters' above and 'Patients with absolute contraindications to anticoagulation' above.)

●Distal DVT – Up to 40 percent of distal DVT (figure 1) resolve without treatment, however, some progress into the proximal veins where they can embolize to the lung. Treatment of acute distal DVT is based on proximal extension (table 6) and bleeding risk (table 3):

•High proximal extension risk and low bleeding risk – For these patients, we suggest anticoagulation rather than serial monitoring with compression ultrasonography (CUS) (Grade 2C). (See 'High extension risk and low bleeding risk: Anticoagulation' above and 'Assess risk of proximal extension' above.)

•Low proximal extension risk OR high bleeding risk – For these patients, we suggest surveillance ultrasonography rather than anticoagulation or IVC filter placement, respectively (Grade 2C). In untreated patients at low extension risk, limited data suggest a low likelihood of proximal extension and embolization. We perform weekly CUS for two weeks.

If the thrombus propagates into the proximal veins during surveillance, then anticoagulation should be initiated (or IVC filter placed), as with patients who present with proximal DVT.

For patients in whom thrombus propagates proximally, but remains confined to the distal veins, we suggest anticoagulation as long as bleeding risk is deemed to be acceptable (Grade 2C). (See 'Low risk of extension: Serial ultrasound' above and 'High extension risk and low bleeding risk: Anticoagulation' above and 'Serial compressive ultrasound protocol' above.)

●Anticoagulation therapy

•Initial anticoagulation – In most patients, anticoagulation should be started immediately as a delay in therapy increases the risk of potentially life-threatening embolization. Selecting an anticoagulant, dosing for parenteral and oral anticoagulants, and empiric anticoagulation are discussed in detail separately. (See "Venous thromboembolism: Initiation of anticoagulation" and "Venous thromboembolism: Anticoagulation after initial management", section on 'Selection of agent'.)

•Outpatient anticoagulation – Outpatient anticoagulation is safe when criteria are met (table 4). It is not appropriate in patients with massive DVT (eg, iliofemoral DVT, phlegmasia cerulea dolens), a high risk of bleeding on anticoagulant therapy, comorbid conditions, or other factors that warrant in-hospital care. If there is concurrent PE, selection criteria for outpatient PE management should be employed (table 5). (See 'Outpatient therapy' above.)

•Duration of anticoagulation – In general, we treat for a minimum of three months. Further discussion on duration of therapy and indications for indefinite anticoagulation are discussed in detail separately. (See "Venous thromboembolism: Anticoagulation after initial management", section on 'Duration of treatment phase and transition to extended phase' and "Selecting adult patients with lower extremity deep venous thrombosis and pulmonary embolism for indefinite anticoagulation".)

●Thrombolytic therapy and thrombectomy – Thrombolytic therapy and/or thrombectomy are usually reserved for patients with phlegmasia cerulea dolens or massive iliofemoral DVT or for patients who fail therapeutic anticoagulation. Thrombolytic therapy is discussed in detail separately. (See "Catheter-directed thrombolytic therapy in deep venous thrombosis of the lower extremity: Patient selection and administration".)

●Special populations – Additional management considerations may be required in patients with malignancy or inherited or acquired clotting disorders. (See 'Special populations' above.):

●Ambulation and graduated compression stockings – For most patients with acute DVT of the lower extremity who are fully anticoagulated, hemodynamically stable, and whose symptoms are under control (eg, pain, swelling), we encourage early ambulation in preference to bed rest. (See 'Ambulation' above.)

We suggest against the routine use of elastic graduated compression stockings to prevent post-thrombotic (postphlebitic) syndrome (PTS) (Grade 2C). One randomized trial suggested no benefit and many patients find them uncomfortable, costly, and inconvenient. GCS may be applied for symptom control or established PTS, the details of which are discussed separately. (See 'Graduated compression stockings' above and "Post-thrombotic (postphlebitic) syndrome in adults", section on 'Management'.)

ACKNOWLEDGMENT — 

The UpToDate editorial staff acknowledges Russell D Hull, MBBS, MSc who contributed to earlier versions of this topic review.