Vascular Medicine & Internal Medicine & Family Medicine
Deep vein thrombosis (phlebitis)
Get advice tailored to your situation
In-person or telemedicine consultations, anywhere in Quebec.
Deep vein thrombosis (DVT) - commonly referred to as phlebitis in everyday language - is the formation of a thrombus (blood clot) in the deep venous system, most often affecting the veins of the lower limbs (tibial, popliteal, superficial femoral, common femoral, iliac) and, more rarely, the veins of the upper limbs (axillosubclavian thrombosis), mesenteric veins or cerebral venous sinuses. DVT and pulmonary embolism (PE) - migration of a thrombus fragment into the pulmonary arterial circulation - together constitute venous thromboembolic disease (VTE), a unique pathological entity with a spectrum of severity ranging from asymptomatic distal DVT to fatal massive PE. VTE represents the third leading cause of cardiovascular death after myocardial infarction and stroke, with an annual incidence of 1 to 2 events per 1,000 people in Western countries, and an early PE-related mortality of 1 to 8 % depending on severity. Its pathophysiology is based on Virchow's triad - venous stasis + endothelial injury + hypercoagulability - with one or more of these elements present in every case of DVT. Venous stasis (prolonged immobilization, bed rest, venous insufficiency), acquired thrombophilic risk factors (active cancer, recent surgery, estroprogestogenic contraception, pregnancy, anti-phospholipid syndrome) and constitutional risk factors (mutations in factor V Leiden, prothrombin G20210A, protein C, S or antithrombin deficiencies) combine to determine the individual risk of thrombosis. Contemporary management has been profoundly transformed by the advent of direct oral anticoagulants (DACs or NACOs - rivaroxaban, apixaban, dabigatran, edoxaban), which have replaced warfarin as the reference anticoagulant treatment thanks to their equivalent efficacy, improved bleeding safety, and the absence of any need for INR monitoring.
Risk factors and Virchow's triad
- Venous stasis prolonged immobilization (bed rest > 72 hours + long plane or car trip > 4–6 hours + cast or splint on lower limb) + chronic venous insufficiency + congestive heart failure + extrinsic compression (tumor + hematoma + adenopathy)
- Endothelial lesion Recent surgery (maximal risk in the first 4 weeks — prosthetic orthopedic hip and knee surgery ++ + neurosurgery + oncological abdominal surgery) + vascular trauma + central venous catheterization + cytotoxic chemotherapy (direct endothelial toxicity)
- Acquired hypercoagulability Active cancer (paraneoplastic coagulopathy — 4 to 7-fold increased VTE risk) + pregnancy and postpartum (physiologic hypercoagulable state + caval compression by uterus) + estrogen-progestin oral contraceptives (3 to 5-fold risk — particularly with second-generation levonorgestrel) + oral menopausal hormone therapy (oral route) + antiphospholipid syndrome (APS) + nephrotic syndrome + chronic inflammatory diseases
- Hereditary Thrombophilias mutation du facteur V Leiden (résistance à la protéine C activée) — la plus fréquente (5 % population générale + risque × 3 à 8 chez l'hétérozygote) + mutation de la prothrombine G20210A (2 %) + déficit en protéine C + protéine S + antithrombine (rares mais risque thrombotique élevé) + hyperhomocystéinémie
Wells Score - Pre-test Clinical Probability
| Clinical criterion | Points |
|---|---|
| Active cancer (treatment ongoing or within the last 6 months + palliative care) | +1 |
| Paralysis + paresis + recent cast on lower limb | +1 |
| Bed rest for more than 3 days or major surgery within 12 weeks (under general or regional anesthesia) | +1 |
| Localized tenderness along the course of the deep venous system | +1 |
| Unilateral whole leg edema | +1 |
| Calf swelling > 3 cm compared to the asymptomatic side (measured 10 cm below the tibial tuberosity) | +1 |
| Dependent edema (pitting edema) on the symptomatic side only | +1 |
| Dilated superficial non-varicose veins (collateral) | +1 |
| Alternative diagnosis at least as likely as DVT | -2 |
| Interpretation : score ≤ 0 = low probability + score 1–2 = moderate probability + score ≥ 3 = high probability |
Diagnostic approach
- D-dimers (high-sensitivity ELISA test): high fibrin degradation products + if thrombus present but not very specific (also high in infections + cancers + pregnancy + post-operative + elderly people) + high negative predictive value (> 97 %) if negative → rule out DVT if low or moderate clinical probability (Wells ≤ 2) + useless if high probability (proceed directly to echo-Doppler) + age-adjusted threshold: 500 µg/L standard + or age × 10 µg/L for patients > 50 years (reduces age-related false positives)
- Venous Doppler ultrasound of the lower extremities - reference examination: visualize the thrombus + test vein compressibility (incompressible vein = thrombus) + evaluate color Doppler flow + sensitivity 90-95% % for proximal DVTs + less sensitive for distal DVTs (tibial veins) + non-invasive exam + no radiation + available in emergencies + repeat on D5-D7 if negative with moderate to high clinical probability (possible evolution of distal DVT to proximal)
- Thrombophilia workup — when to prescribe: TVP or PE in young subjects(Under 50 years old) without obvious risk factors + recurrent DVT + family history of VTE in a first-degree relative + unusual location (mesenteric + caval + cerebral venous sinus) + not to be performed during the acute phase or while on anticoagulants (biased results) + refer to hematology or internal medicine for workup
ℹ️
Optimal diagnostic algorithm: assess Wells score → if score ≤ 1 + negative D-dimers → DVT excluded without imaging. If score ≤ 1 + positive D-dimers → Doppler ultrasound. If score ≥ 2 → Doppler ultrasound directly without D-dimers (D-dimers do not exclude high-probability DVT). Negative Doppler ultrasound with moderate-high probability → repeat at day 5-7 or venous scan if ilio-caval DVT suspected (not visualized on standard ultrasound).
Anticoagulant therapy
| Anticoagulant | Dosage and protocol | Preferential Indications and Remarks |
|---|---|---|
| Rivaroxaban (Xarelto®) — First-line NOAC | 15 mg twice daily for 21 days (initial phase) → then 20 mg once daily (maintenance and extended prophylaxis phase) + with evening meal (improves absorption) + no INR monitoring | First-choice NACO in Canada for non-massive DVT and PE + EINSTEIN-DVT trial: non-inferior to warfarin + fewer major bleeding events + antidote: andexanet alfa (Ondexxya®) for severe bleeding + to avoid if GFR < 15 mL/min + pregnancy + antiphospholipid syndrome (risk of failure) |
| Apixaban (Eliquis®) — First-line NOAC | 10 mg twice daily for 7 days (initial phase) → then 5 mg twice daily (maintenance phase) → then 2.5 mg twice daily (extended prophylaxis if beneficial) + with or without food | Alternative to rivaroxaban + AMPLIFY trial: equivalent efficacy to warfarin + fewer major hemorrhages + favorable safety profile in moderate renal insufficiency + antidote: andexanet alfa + better gastrointestinal tolerance than dabigatran |
| Dabigatran (Pradaxa®) | Requires initial parenteral treatment 5–10 days (LMWH or fondaparinux) → then dabigatran 150 mg × 2/day (or 110 mg × 2/day if ≥ 80 years old or high bleeding risk) | Specific antidote: idarucizumab (Praxbind®) — beneficial if high risk of severe hemorrhage requiring rapid reversal + less prescribed than rivaroxaban and apixaban in Canadian practice for DVT + to be avoided if GFR < 30 mL/min |
| LMWH (low molecular weight heparin) | Enoxaparin (Lovenox®) 1 mg/kg SC × 2/day OR Tinzaparin 175 IU/kg SC × 1/day + weight-adjusted dose + anti-Xa monitoring if moderate CKD + morbid obesity + pregnancy | Standard treatment during pregnancy (NOACs are contraindicated) + active cancer (superior to warfarin - CATCH + CLOT studies) + increasingly replaced by NOACs in patients with cancer (NOACs approved in oncology) |
| Warfarin (Coumadin®) | Initial dose 5–10 mg/day → adjust according to INR (target INR 2–3) + daily INR during initial phase → space out to weekly then monthly if stable + numerous food (vitamin K) and drug interactions | Less and less used for DVT/PE (replaced by DOACs) + still indicated in APS (target INR 2.5–3.5 if arterial thrombosis) + and if DOACs are contraindicated + mandatory monthly INR monitoring + antidote: vitamin K + fresh frozen plasma + prothrombin complex concentrate (PCC) |
Duration of anticoagulant treatment
- Symptomatic isolated distal TVP (below the knee) 3 months + if transient risk factor resolved + low recurrence risk + oral anticoagulant for 3 months then stop + if risk factor persistent or recurrent -> discuss extension
- Proximal TVP or PE + major transient risk factor (surgery + trauma): 3 months + very low risk of relapse after stopping if risk factor resolved
- Proximal TVP or unprovoked PE (without identified risk factors): minimum 3 months, then individual reassessment of the benefit/risk ratio of prolonged anticoagulation plus recurrence risk scores (HERDOO2 + Vienna + DASH) + if high recurrence score → indefinite prolongation + if low bleeding risk → extended prophylaxis at low dose (rivaroxaban 10 mg/day or apixaban 2.5 mg twice daily)
- TPN or PE associated with active cancer: minimum duration of 6 months + often indefinite treatment as long as cancer is active or undergoing treatment + NOAC (rivaroxaban or apixaban) or LMWH depending on cancer type and gastrointestinal bleeding risk
- Major thrombophilia (protein C/S/antithrombin deficiency + APLS + FVL double heterozygosity + prothrombin): indefinite anticoagulation often recommended after a first episode if major thrombophilia documented
Post-thrombotic syndrome and non-pharmacological measures
- Post-thrombotic syndrome (PTS): chronic complication occurring in 20 to 50 % of patients after proximal DVT + results from valvular sequelae and chronic venous hypertension → pain + edema + heaviness + leg cramps + lipodermatosclerosis + venous leg ulcer in severe forms + prevention: class 2 compression stockings (20–30 mmHg) worn from diagnosis and for at least 2 years + 50 % reduction in moderate to severe PTS with compression (SOX trial — nuanced results)
- Elastic compression: Class 2 anti-thrombosis or compression stockings to be worn during the day from waking until bedtime, plus throughout the duration of anticoagulant treatment. Reduces acute pain and swelling. Prevents post-thrombotic syndrome. Formal indication for symptomatic proximal deep vein thrombosis.
- Early mobilization: Active walking as soon as pain allows (Day 1 if possible) → improves venous return + reduces thrombus extension + reduces pain + bed rest is no longer routinely recommended for uncomplicated DVT
Emergency — call 911 if pulmonary embolism is suspected
Call 911 or go to the emergency room immediately if a suspected or known DVT is accompanied by sudden onset dyspnea + chest pain + tachycardia + or hemoptysis (coughing up blood) — these signs suggest a pulmonary embolism, a potentially fatal complication of deep vein thrombosis requiring absolute emergency evaluation and management. An oxygen saturation below 94 % or a heart rate above 100/min in a patient with DVT is a red flag that should prompt an immediate call to 911.
For the assessment of suspected DVT (pain + swelling + unilateral redness of a leg), calculating the Wells score, prescribing D-dimers and Doppler ultrasound, and initiating anticoagulant therapy, Clinique Omicron offers medical consultations at its service points in Quebec and via telemedicine. To make an appointment, visit cliniqueomicron.ca.
Consult at Clinique Omicron
Clinique Omicron's nurse practitioners (NPs) and physicians assess patients with suspected DVT using the Wells score, order D-dimer tests and lower limb venous Doppler ultrasounds, initiate anticoagulant treatment with NOACs upon confirmed diagnosis, prescribe compression stockings, and monitor the optimal duration of anticoagulation—referring complex cases (thrombophilia + cancer + APS + recurrences) to internal medicine or hematology. Consultations are available at several service points in Quebec and through telemedicine. To book an appointment, visit cliniqueomicron.ca.
The content of this page is provided for informational purposes only and does not replace the advice of a doctor or a vascular medicine specialist. Any shortness of breath or chest pain in a patient with DVT should lead to an urgent medical evaluation to rule out pulmonary embolism.
Omicron Clinic
Need to consult a doctor?
In-person or via telemedicine, anywhere in Quebec.
We accept insurance. Telemedicine consultations available 7 days a week. No family doctor required.