I had UC. (I've had my colon removed now)
I was diagnosed by a gastro consultant, who used a scope to look at the very end of my bowel (UC always starts at your bottom and spreads further in as it gets worse, crohns can start anywhere in the digestive tract so might not be visible that way). I was then referred for a flexi sigmoidoscopy, which is like half a colonoscopy, to see how bad it was.
I take it he's on no medication at all at the moment?
It sounds like - if it is IBD - he needs steroids to get this flare under control, then a treatment plan to maintain that.
Does he have a date for any appointments yet? The urgent referral, is that on a two week wait?
If he gets really bad, lots of pain, lots of blood, worried about dehydration, that sort of thing then it would be reasonable to go to A&E. Has he been given any warning signs to watch out for and seek medical attention?
Also, I'd hope he's been told this, but just in case - he mustn't take anything like immodium, it can be dangerous.