Findings for the diagnosis of acute DVT on CT venography include an intravascular filling defect of low density or total lack of enhancement of a venous region (Fig. 13) [13,28,29]. Ancillary findings of DVT are enlargement of the thrombosed vein, wall enhancement, and perivenous edema (Fig. 14). With acute occlusive thrombosis, the vein enlarges, sometimes to twice the size of the accompanying artery. The vein wall may enhance to a density equal to or higher than muscle density. An additional finding seen in DVT is a focal perivenous soft-tissue infiltration that is probably due to local edema. This finding, not specific for DVT, is most easily detectable in the thigh and popliteal regions where fat surrounds the veins.
For the diagnosis of chronic DVT on CT venography, we have used criteria analogous to criteria used in venography to identify chronic thrombus. In chronic disease, the vein is often smaller than the accompanying artery (Fig. 15), may be calcified, and may not carry contrast-enhanced blood. In addition, extensive collateral veins are an indication that chronic disease is
Figure 15 Chronic DVT. CT venography image in patient with chronic DVT. The right superficial femoral vein (arrowhead) is small; compare with that of the normal left superficial femoral vein.
present. Their presence, however, does not rule out acute clot superimposed on chronic clot.
Computed tomography venography can define additional disease (e.g., focal venous aneurysm, abdominal tumor, muscle hematoma, bone fractures, and arterial thrombosis) that has an impact on patient management . Occasionally, incidental findings that will not necessarily affect patient management are revealed, such as a Baker's cyst, or suprapatellar effusions [28,29].
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