DVT

Question 1

How common is it?

Answer 1

Annual incidence of about 1 in 1000 people (0.1%)

Question 2

What causes it?

Answer 2

Thrombosis can occur in any vein, but those in the pelvis and leg are the most common sites. Can be classified as provoked/unprovoked. Unprovoked counts as DVT in the absence of a transient risk factor (e.g. long haul flight)

Question 3

What risk factors are there?

Answer 3

Intrinsic: Previous. venous thromboembolism, cancer, age over 60, being overweight, male sex, heart failure, severe infection, acquired or familial thrombophilia, chronic low-grade injury to the vascular wall, chronic low-grade injury to the vascular wall (for example vasculitis, hypoxia from venous stasis, or chemotherapy), varicose veins, smoking.

Risk factors that temporally rise the likelihood of DVT include: Immobility significant trauma or direct trauma to a vein (e.g. intravenous catheter). Hormone treatment. Pregnancy and the post-partum period. Dehydration.

Question 4

How does it present?

Answer 4

Often asymptomatic but the leg may be warm and swollen, with calf tenderness and superficial venous distention. Changes to skin colour.

Question 5

Investigations

Answer 5

D-dimer
Venous compression ultrasonography is indicated as a reliable test for iliofemoral thrombosis, but not for calf vein thrombosis.

You would also use the Wells score for the clinical probability of a DVT.

Question 6

Treatment

Answer 6

Perform a coagulation screen and platelet count before starting treatment to exclude a pre-existing thrombotic tendency.

LMWH where feasible selected patients can be safely treated as outpatients, warfarin is started at the same time. The dose of warfarin is adjusted to maintain the INR, usually at two to three times the control value.

Heparin is overlapped with warfarin for a minimum of 5 days and continued until the INR is in the therapeutic range.

Question 7

Conditions that would present similarly

Answer 7

Trauma: Calf muscle tear or strain, haematoma in the muscle, sprain or rupture of the Achilles tendon. Fracture.

Cardiovascular: Superficial thrombophlebitis, post-thrombotic syndrome, venous obstruction or insufficiency, or external compression of major veins (e.g. due to cancer or pregnancy). Arteriovenous fistula and congenital vascular abnormalities. Acute limb ischaemia, vasculitis, heart failure.

Other: Ruptured Bakers cyst, cellulitis, dependent (stasis) oedema, lymphatic obstruction, septic arthritis, cirrhosis, nephrotic syndrome, compartment syndrome.