Hey guys! So since the beginning, I've read that if we are ever experiencing abdominal pain and go to the ER that we have to demand a CT scan with IV contrast. I understand that drinking the liquid will not show a potential obstruction in the bilio-pancreatic limb since food and liquids don't pass through that section. What I don't understand is how exactly an IV contrast will show an obstruction? Doesn't the contrast go through the blood vessels? Will it show the lack of blood flow to part of the biliopancreatic limb if there's an obstruction or is it something else? And before anyone jumps down my throat, I'm not experiencing any pain, I saw a thread on another site that was upsetting and just got me thinking that I don't 100% understand how it works. Thanks!