I was initially diagnosed with proctitis. I always found that statistic that proctitis very rarely spreads to be odd. If you have proctitis, it seems like, it's often the start of something worse, or it's not, but 10% sounds low.
I would ask for stool tests for sure. I'd also ask about
doing blood work and see if s/he has a plan to take a look with a flex sig or a colonoscopy. That's the best tool to see what's going on and get biopsies. They will walk you through, but make sure you request stool tests.
Oh yes, and ask for rectal meds if it's in the rectum.