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Department
of Podiatry - Vascular Assessment
Deep
Venous Thrombosis (DVT)
Deep
Vein Thrombosis (DVT) is a thrombus formation in a deep vein of the body.
DVT’s are of interest to the podiatrist as they commonly inhabit
the femoral vein (Mosby, 1998). Patients presenting with symptoms of a
DVT are considered high-risk patients because of the sequelae that may
follow.
Three predisposing factors are always present in the development of DVT,
known as Virchow’s Triad: vessel wall injury, blood stasis, and hypercoagulability
(Baele, 1992).
Damaged endothelium may be caused by direct trauma, infections of surrounding
soft tissue, intravenous catheters or prolonged use of them. The trauma
reveals subendothelial tissue which releases platelet activating factors,
initiating coagulation cascade, results in platelet adhesion to the wall
and the beginning of thrombus formation (LTU PM331 manual).
Blood stasis in the veins interferes with nutrition to the endothelial
lining, rendering the wall susceptible to minute thrombus formation (LTU
PM331 manual). Causes of venous stasis are immobilization or inactivity,
typically following a stay in hospital, long plane flight, application
of a cast, illness, or caused by poor deep venous muscle pump from apropulsive
gait. Stasis may also be caused by sluggish or impaired venous return
to the heart following CVA, congestive heart failure, myocardial infarct,
and valvular incompetence (Cotran, 1999; Nelson, 1992).
Hypercoagulability of blood may be caused by haematological conditions
such as anaemia and polycythemia vera, through infectious disease such
as typhoid and pneumonia, as a secondary complication to nephrotic disease,
or hypercoagulable drugs and oral contraceptives (Cotran, 1999; LTU PM331
manual).
DVT typically presents as unilateral inflammation with redness, warmth,
and indurated oedema. Pain and discomfort may
be present depending on the severity of the occlusion. Homan’s sign
is 50% accurate for DVT, and is characterised by discomfort in the upper
calf with dorsiflexion of the foot (Baele, 1992).
As mentioned above, the sequelae following DVT may cause serious complications,
including sudden death. The most important of these is when part of the
thrombus breaks off to form an embolism, which can lodge in a lung and
give rise to pulmonary embolism.
More localised effects of DVT are damage to surrounding valves and superficial
veins due to the venous hypertension, and the damage caused by prolonged
oedema.
This picture
shows deep vein thrombosis with phlebitis in the leg. Note the swelling
and discoloration of the left leg.
Directional
ultrasound: acute DVT with a floating thrombus in the superficial femoral
vein.
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