If I were you, I will go ER directly. You will have all of the tests (include lab work for blood, urine, feces, CT scan or X-Ray) done there and ER doctor visit. But you have to pay ER co-payment. Good luck.
CKD People with UTI and other urinary issues should be very alert to the possibility of it causing further kidney damage. I would get it checked out by whatever medical help you can get.
I know you are having trouble with diarrhea now, but when taking laxatives, make sure your blood test are okay. Laxatives can decrease the amount of nutrition you absorb from your food. I am sorry you are going through so much pain! Praying the diarrhea stops soon!
Anything you drink goes to the kidneys, so I am not sure why he thinks oral dye would not. I would be very skeptical of this and ask your nephrologist for his/her opinion. MRI's are very safe. Just don't wear any metal and let them know if you have metal inside you.
A radical option - but one that isn't feasible for any kidney patient - is to take a one of those bowel pre-operative prep solutions (they come in enema format & can clean everything out within 2-5 minutes apparently). But it is contraindicated in renal impairment as well as those taking calcium channel blockers. Sodlum, phosphate & calcium electrolyte levels can be severely affected by this dangerous substance.