2. What is it? A deep vein thrombosis is a condition where the blood clots in a distal, deep vein A blood clot is considered a thrombosis as long as it is stationary in the vein. If it becomes dislodged it is considered an embolism An embolism can become a life threatening condition if the clot gets lodged into a pulmonary artery

3. How does it develop? Virchow's Triad describes how a DVT develops – Decreased rate of blood flow in a vein – Damage to the wall of that vein – Increased tendency for hypercoagulability Many DVT’s are asymptomatic

4. Examination Homan’s Sign – This test uses dorsiflexion of the ankle and gentle squeezing of the lower leg – A positive sign is pain in the deep calf area – This test is not very specific since there are other structures or conditions that can reproduce similar pain

5. Examination Well’s clinical decision rule for DVT – Done by taking a clinical survey Risk score interpretation (probability of DVT): – >/=3 points: high risk (75%) – 1 to 2 points: moderate risk (17%) – <1 point: low risk (3%) Clinical featurePoints Active cancer (treatment within 6 months, or palliation) 1 Paralysis, paresis, or immobilization of lower extremity 1 Bedridden for more than 3 days because of surgery (within 4 weeks) 1 Localized tenderness along distribution of deep veins 1 Entire leg swollen 1 Unilateral calf swelling of greater than 3 cm (below tibial tuberosity) 1 Unilateral pitting edema1 Collateral superficial veins1 Alternative diagnosis as likely as or more likely than DVT -2 Total points

6. Treatment Refer out Treatments – Medication to make the clot smaller – Surgery to remove the blood clot – Prevention to limit the build up of further clots

7. References Goodman CC, Snyder TE. Differential Diagnosis for Physical Therapists: Screening for referral. 2007.