A suspicion of a thrombotic occlusion of the vein passed by the catheter indicates a [[CT angiography]].<ref name=Helsingborg/>
===Preparation===
Ability to aspirate from the catheter can optionally be tested.
*Contrast should be non-ionic,<ref name="KnutstadHager2016"/> with an iodine concentration of at least 270 mg/ml.<ref name=Helsingborg/>