page_title: Deep vein thrombosis
section_title: Classification
hierarchical_section_title: Deep vein thrombosis / Classification
context_page_description: Deep vein thrombosis is the formation of a blood clot in a deep vein, most commonly in the legs or pelvis. Symptoms can include pain, swelling, redness, and enlarged veins in the affected area, but some DVTs have no symptoms. The most common life-threatening concern with DVT is the potential for a clot to detach, travel through the right side of the heart, and become stuck in arteries that supply blood to the lungs. This is called pulmonary embolism. Both DVT and PE are considered as part of the same overall disease process, which is called venous thromboembolism. VTE can occur as an isolated DVT or as PE with or without DVT. The most frequent long-term complication is post-thrombotic syndrome, which can cause pain, swelling, a sensation of heaviness, itching, and in severe cases, ulcers. Also, recurrent VTE occurs in about 30% of those in the ten years following an initial VTE.
  The mechanism of clot formation typically involves some combination of decreased blood flow rate, increased tendency to clot, and injury to the blood vessel wall.
context_section_description: The disease term venous thromboembolism (VTE) includes the development of either DVT or pulmonary embolism (PE) or both simultaneously. Provoked DVTs occur in association with acquired risk factors, such as surgery, oral contraceptives, trauma, immobility, obesity, or cancer; cases without acquired states are called unprovoked or idiopathic. Acute DVT is characterized by pain and swelling and is usually occlusive, which means that it obstructs blood flow, whereas non-occlusive DVT is less symptomatic. The label "chronic" has been applied to symptomatic DVT that persists longer than 10 to 14 days. DVT that has no symptoms, but is found only by screening, is labeled asymptomatic or incidental. An initial episode of DVT is called incident and any subsequent DVT is termed recurrent. Bilateral DVT refers to clots in both legs while unilateral means that only a single leg is affected.
  DVT in the legs is proximal when above the knee and distal (or calf) when below the knee. DVT below the popliteal vein, a proximal vein behind the knee, is classified as distal and has limited clinical significance compared to proximal DVT. Iliofemoral DVT has been described as involving either the iliac or common femoral vein; elsewhere, it has been defined as involving at a minimum the common iliac vein, which is near the top of the pelvis. Upper extremity DVT occurs in the arms or the base of the neck. A rare and massive DVT that causes significant obstruction is phlegmasia cerulea dolens, so named because of observed cases with a blue or purplish discoloration. It is a particularly severe form of acute, proximal, and occlusive DVT. It is life-threatening, limb-threatening, and carries a risk of venous gangrene. It can occur in the arm but more commonly affects the leg.
caption: The iliac veins (in the pelvis) include the external iliac vein, the internal iliac vein, and the common iliac vein. The common femoral vein is visible below the external iliac vein. (It is labeled simply "femoral" here.)
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