Venous intravasation in retrograde urethrography is associated with pre-existing mucosal breaches in inflammatory strictures when contrast enters submucosal venous plexus and intravasation along the venous pathway. Intravasation is partly due to the degree of pressure applied during contrast administration -- the higher the pressure, the more likely intravasation will occur.

It should be reminded that iodinated contrast into the venous circulation may lead to an allergic reaction in susceptible individuals (up to and including anaphylaxis). Consider stopping the procedure when encountering intravasation.