The natural history of a deep vein thrombus in any individual (assuming it does not embolize) is determined by competition between fibrinolysis and the slower process of organization and recanalization. When plasmin activity is high and the clot small, complete dissolution is possible. However, if there is time for organization of the thrombus, permanent anatomic narrowing of the lumen of the vein ensues. Whether clinically recognizable dysfunction results from this anatomic narrowing depends on which vein is affected, and over how great a length.
One common clinical manifestation is edematous swelling of the entire lower limb, associated with venous outflow obstruction at the level of the iliac, common femoral, or superficial femoral veins. Subcutaneous collateral veins are usually visible, running from the groin of the affected limb across to the other groin, or onto the abdominal wall. Phlebography will clearly delineate the site of the obstruction (and also the collateral