Could take as long as 3 hours.
Mentioned by docorion yesterday, verified by dial-a-nurse just now.
I need to call Radiology when I get home and see whether the particular contrast-dye thing they're doing is the three-hour one. Because if it is - dude, I have to show up early. Because my appointment is at 11. Three hours puts me within fifteen minutes of Elayna's school-release time, and I'm not comfortable with cutting things so close!