Fig 2.

Intravascular injection identified by a less-than-expected accumulation of epidural contrast. A, Needle position before the contrast trial dose. B, Only a very small amount of contrast, considerably less than the injected volume of 0.3 mL of iohexol, is seen on immediate postinjection imaging. The missing contrast is inferred to be intravascular and has been circulated out of the imaged field. (A trace amount of intravascular contrast is also noted within the right aspect of the spinal canal.) C, After the needle is withdrawn several millimeters, a repeat contrast trial injection shows the expected volume of injected contrast accumulating in the epidural space. No additional intravascular contrast was identified with the steroid/analgesic injection (not shown), making this a trial dose intravascular injection.