i know there are a few different types of contrasting agents out there that they can use for certain rad scans.i would actually call the place where you are having this done and just simply ask questions.the one big thing about contrast agents that alot of people just are not aware of is that they can be very hard on the kidneys if you have any level of actual kidney disease going on or have a disease that you are just not aware of.i did not even have a clue that polycystic kidney disease ran in our family til my youngest son became gravely ill with liver failure.that is when my kidneys had to have an ultrasound done,along with my hubby too since this was an inhertied disorder.i found out at age 40 that i had this disease all my life but since my labs were always and still are within the norms,it never was Dxed til the US was done.every single rad test i have to have now(there have been many just becasue of my ongoing medical issues)that has to use contrast,i have to drink this smelly sulpher based crap called mucomyst.it justhelps the dye to run thru the kidneys without it being flitered.anytime you have to have certain contrast agents,they should also do a creatinine check for kidney function too.alot depends upon that dye they use for any particular type of testing.some are worse than others.i just treat them all like they are bad for my kidneys and do the muco regardless.but thats my situation.just make that call to the radiology facility that will be doing your test,they would be able to give you the specifics on any contrast agents they may use and what to possibly do as far as checking your creatinine level first.good luck on the test,hope all is okay. FB