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CDHB

Diagnosis of Deep Vein Thrombosis (DVT)

Clinical Features and Causes of DVT

• Suspect DVT if there is swelling, pain, tenderness, and dilated superficial veins.

Causes

• Surgery, immobilization including travel, oestrogen therapy (combined oral contraceptive pill, hormone replacement therapy), malignancy, pregnancy and puerperium, polycythaemia, thrombocytosis.
• Check for family history of VTE.
• Thrombophilia testing is not required for the majority of patients with DVT/PE. If the patient is under 45 years, consider activated protein C resistance (Factor V Leiden), anti-thrombin III deficiency, protein C or protein S deficiencies, prothrombin gene mutation, or antiphospholipid antibody syndrome. These tests should be taken before treatment is started.

Risk Assessment for DVT

Reference: Wells et al. NEJM 2003; 349: 1227-1235.

Note: It is essential to work out the pre-test probability for DVT and write this in the patient's notes.

Investigations for Suspected DVT

Assess the clinical probability of DVT (refer to Risk Assessment for DVT), and get D-dimer result. Then proceed as follows:

• A negative D-dimer in a patient with an "unlikely" pre-test probability score excludes a clinically significant DVT. If the pre-test probability is "likely", consider an ultrasound (USS).
• A positive D-dimer in a patient with suspected DVT needs to be correlated with the pre-test probability score and an ultrasound scan (USS) of the affected leg(s). Then proceed as follows:
  • If the clinical probability is unlikely:
    • and the USS is normal, DVT is for practical purposes excluded. If however the symptoms persist and an alternative diagnosis is not apparent by 48-72 hours, consider a repeat USS. If positive at 72 hours, treat with anticoagulant therapy.
    • and the USS is positive, treat with anticoagulant therapy.
  • If the clinical probability is likely:
    • and the USS is normal or equivocal, consider CT venography (± CTPA), discuss with Radiologist. If there is any delay, consider anticoagulant therapy.
    • and the USS is positive, treat with anticoagulant therapy.

Notes on Investigations for DVT

• The D-dimer assay has a sensitivity for DVT of 89-100% and negative predictive value of 95-100%.
• D-dimer levels may be above the quoted upper limit in otherwise normal elderly patients (>60 years).
• Ultrasound of the femoral and popliteal veins is usually the investigation of choice. A thrombus can be demonstrated and if present the vein will not be compressible. A Doppler ultrasound may also show reduced flow. Ultrasound may sometimes detect calf vein thrombosis (see below).
• If there has been a previous clot, it may be difficult to distinguish post phlebitic changes from a fresh clot. Comparison with earlier ultrasounds and assay of D-dimer may help.
• If the ultrasound is negative for DVT, remember that a ruptured Baker's cyst may produce a similar clinical picture and may also be visualized by ultrasound.

Calf Vein Thrombosis

• About 50% of symptomatic DVTs will be limited to the calf veins. 10% of these will extend into the proximal veins putting the patient at risk of PE.
• The management of calf vein thrombosis is controversial and requires balancing the risk of DVT extension against the risks of anticoagulation.
• 4-6 weeks anticoagulation (LMWH and warfarin), or longer if clinically indicated, does reduce the risk of extension and PE.
• If anticoagulation is not offered, then close monitoring with repeat USS at 48-72 hours is recommended to check whether clot extension has occurred. Consider a further repeat at 10-14 days if signs persist.

Note: When management of calf vein thrombosis is uncertain, discuss with the Haemostasis Service.

DVT in Patients with Cancer

The decision to give anticoagulants in this situation needs to be individualized. It may be inappropriate to initiate such treatment in patients with extensive metastatic disease with limited life expectation. In most cases, patients with VTE and active cancer require immediate treatment with therapeutic doses of LMWH and this should be given for 3-6 months.

At that time a decision to continue LMWH, change to warfarin, or to stop anticoagulants must be taken. Factors to consider are: is the cancer in remission or active, is any ongoing cancer treatment prothrombotic, and what treatment (if any) would the patient prefer?

Superficial Venous Thrombosis of the Lower Limb

Superficial venous thrombosis has replaced the term 'thrombophlebitis' as it is more descriptive and implies the recently established link to DVT.

• This remains primarily a clinical diagnosis, with pain, tenderness, erythema, and induration along the course of a vein.
• Risk factors include: venous stasis, e.g., varicose veins, pregnancy, infection, thrombocytosis, polycythaemia and cancer.
• 5% of patients presenting with superficial venous thrombosis will also have a DVT. For the remainder there is a 10% risk of extension to the deep veins over the next 10 days.

Management

• An ultrasound to exclude DVT should be done if there is an involved segment of vein of >5 cm, the saphenous vein is involved, and/ or there is significant leg swelling. If DVT is present treat accordingly.
• If there is no DVT, but superficial venous thrombosis is confirmed and:
  • The superficial venous thrombosis is within 3 cm of the sapheno-femoral junction, consider treatment as for DVT.
  • There are one or more of the above risk factors, consider prophylactic doses of LMWH for 30 days.
  • None of the above risk factors are present, consider conservative treatment with elevation of the limb, compression stockings, and pain relief. If evidence of infection, treat as appropriate.
• Follow up at 7-10 days or earlier if there is deterioration. If no resolution at this time, repeat the ultrasound.
• If superficial venous thrombosis is diagnosed clinically, give conservative treatment and follow-up as above.

Reference: Tait et al, BJH, Guidelines on the investigation and management of venous thrombosis at unusual sites. BJH 2012.159 pp 28-38.

Upper Extremity Deep Vein Thrombosis

• Accounts for up to 10% of all DVTs, but primary causes are rare.
• May affect axillary, subclavian, or brachial veins.
• Are considered primary if idiopathic or associated with the thoracic outlet syndrome or effort. If there is a definite cause they are regarded as secondary.
• Primary upper limb DVT is rare. The average age at presentation is the early thirties. It is associated with strenuous activity, especially involving repetitive arm movements. A thrombophilic defect may also be present.
• Secondary causes include: central venous catheters (CVC), active malignancies, inherited and acquired thrombophilia.

Investigations

• Venography or compression ultrasound to establish the diagnosis. CXR.
• If the condition is primary, a thrombophilia screen should be taken before treatment is given.

Management

This depends on the cause and the severity of the venous occlusion. Search for risk factors.

• Secondary:
  • Give 4-5 days LMWH and warfarin for 3 to 6 months. See Treatment of VTE.
  • If associated with the presence of a CVC, then this will usually, but not always, need to be removed.
  • If associated with active cancer, consider LMWH for 3 months or for as long as clinically appropriate. See DVT in Patients with Cancer.
• Primary:
  • Start LMWH and warfarin as for lower limb DVT. Consult a Haematologist re ongoing management.
  • If severely affected and/or associated with thoracic outlet obstruction or effort, such patients are likely to have long term problems with persisting venous obstruction. In this situation, consultation with Vascular Surgery is also recommended as thrombolysis with or without surgery may be indicated; thrombolysis is most effective if carried out within 7-10 days of onset.

Topic Code: 38596