What does a filling defect with a "string of pearls" sign suggest in venography?

A filling defect with a "string of pearls" sign in venography is indicative of acute deep vein thrombosis (DVT). This sign occurs when clots form in the deep veins, leading to a pattern of filling defects due to the presence of multiple small thrombi along the vein, resembling a string of pearls. The visualization of these defects suggests that blood is unable to flow through the affected area because of the obstruction caused by the thrombi.

In acute DVT, these filling defects can be seen as the thrombus forms rapidly and can be evaluated through venography, which shows the outline of the vein and any obstructions. The presence of this specific pattern is a critical diagnostic observation that helps differentiate acute DVT from other vascular conditions.