In venography, what indicates the presence of acute DVT?

In venography, the presence of acute deep vein thrombosis (DVT) is indicated by areas of no contrast accompanied by "railroad track" lines. This visual pattern occurs when there is blood flow obstruction caused by a thrombus, preventing the contrast medium from filling the vein. The "railroad track" appearance is characterized by the outlines of the vein walls (which are not filled with contrast) that appear side by side. This representation is a direct indication of a clot blocking the normal flow of blood, corroborating the diagnosis of acute DVT.

Other options do not suggest DVT effectively. Widely patent veins indicate normal venous patency and flow, which suggests the absence of thrombosis. High blood flow with collateral formation might indicate a compensatory response to an obstruction, but it does not directly correlate to the presence of an acute thrombus within the veins themselves. Increased contrast uptake might imply a quicker filling of certain areas but does not denote the presence of a thrombus specifically. Therefore, "railroad track" lines provide the most definitive visual evidence of acute DVT during venography.