Deep Vein Thrombosis

Original Editor - Jennifer Self

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Clinically Relevant Anatomy

Muscle veins drain into the deep veins of the lower extremity. Soleal muscle veins drain into the peroneal and tibial posterior veins. Gastrocnemius veins drain into the popliteal vein. Thrombosis usually develops as a result of venous stasis or slow-flowing blood around venous valve sinuses. Extension of the primary thrombosis occurs within or between the deep and superficial veins of the leg, and the propagating clot causes venous obstruction, damage to valves, and possible venous thromboembolism.

Mechanism of Injury / Pathological Process

A deep vein thrombosis (DVT) is a vascular disease which consists of venous stasis and hypercoagubility in the venous system and at times can become mobile and result in a pulmonary embolus and potentially death.

See image of DVT here

Clinical Presentation

Clinical features of a DVT include:

• Sweling of the extremity
• Tenderness or a feeling of cramping of the calf muscles that is increased with dorsiflexion (Homan's sign)
• Inflammation and discoloration/redness of the extremity

Clinical features of a Venous Thromboembolism include:

• Calf pain and/or tenderness
• Swelling with pitting edema
• Swelling below the knee (distal deep vein thrombosis) or up to the groin (proximal deep vein thrombosis)
• Increased skin temperature
• Superficial venous dilation
• Cyanosis in patients with severe obstruction

Clinical Prediction Rule

The following clinical prediction rule can help a clinician identify a DVT.

1. Active cancer (treatment ongoing, within previous 6 months, or palliative)= 1 point
   
2. Paralysis, paresis, or recent plaster immobilization of the lower extremities= 1 point
   
3. Recently bedridden for > 3 days or major surgery within 4 weeks= 1 point
   
4. Localized tenderness along thte distribution of the deep venous system. Tenderness along the deep venous system is assessed by firm palpation in the cneter of the posterior calf, the popliteal space, and along the area of the femoral vein in the anterior thigh and groin= 1 point
   
5. Entire lower extremity swelling= 1 point
   
6. Calf swelling > 3 cm when compared with the asymptomatic lower extremity. Measured with a tape measure 10cm below the tibial tuberosity= 1 point
   
7. Pitting edema (greater in the symptomatic lower extremity)= 1 point
   
8. Collateral superficial veins (nonvaricose)= 1 point
   
9. Alternative diagnosis as likely or greater than that of proximal DVT. More common alternative diagnoses are cellulitis, calf strain, Baker Cyst, or postoperative swelling= -2 points
   

The total score for all items is tallied and the probability of the patients having a DVT are as follows:

0= low, 1-2=moderate,and ≥3=high

Diagnostic Procedures

Homans' Sign: The patient's foot is passively dorsiflexed with the knee extended. Pain in the calf indicates a positive Homans' sign for DVT. Tenderness is also elicited upon palpation of the calf.

• +Likelihood ratio= 1.40
  
• -Likelihood ratio= .87
  

D-Dimer testing: a simple blood test of fibrin degradation. D-dimer levels in the blood are increased by any condition that produces fibrin; this testing has been found to be the most useful blood marker of fibrinolysis. The negative likelihood ratio is higher than 99%. This test is best used on outpatients with a low probability of PDVT, based on the use of the CDR by Wells & colleagues.

Compression ultrasound/Duplex Ultrasound: This is a diagnostic procedure involving the use of a 3-7.5 MHz transducer to produce an image of the involved vein. This is considered to be the first-choice diagnostic test for patients with symptomatic PDVT in the moderate to high probability groups, based on the use of the CDR by Wells & colleagues. Sensitivity and specificity for compression ultrasonography average 95% for detection fo PDVT.

Venography: This is considered the gold standard test for PDVT, but this test is invasive and carries some risk. This procedure involves an x-ray of the veins (venogram) taken after a special dye is injected into the bone marrow or veins.

Outcome Measures

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Management / Interventions

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Differential Diagnosis

Potential causes for calf pain:

• Pyomyositis
• Fibula shaft fracture
• Deep vein thrombosis
• Hematoma
• Rupture of Achilles Tendon
• Soleus muscle strain
• Acute posterior compartment syndrome
• Muscle cramps

Key Evidence

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Resources

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Case Studies

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Recent Related Research (from Pubmed)

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References

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