Why would my doctor order a bun/creatine test with the abdominal/pelvic ctscan? the place where theyll do the test said i gotta do the bun/creatine first then the ct, why?

If you have kidney failure the amount of IV dye.has to be lessened and IV hydration may be needed before using iodine based contrast. I believe gadolinium contrast may not be used in the presence of kidney dysfunction.

It is important to test for renal function before injecting radio-contrast media/dye as some of the dyes are injurious to the kidney. A diseased kidney is more susceptible to injury from dyes. Wish you good health!