[ath.pantelis]

I agree with dr. laithbv. The fact that this pt suffers from CD over a long period is both helpful and distracting. It's helpful, because it indicates this pt's tendency to develop calcium oxalate stones through the urinary system, a scenario that is compatible to the distribution of pain troughout the course of the left ureter. At the same time, one may focus on Crohn's disease itself, not give much attention to the pain (considering that it is part of the intestinal syndrome), and thus miss the differential of urinary stones.

With these arguments in mind, I think that the correct answer is hCT without contrast (b); this is the only imaging study among the rest that can prove the existence a urinary calculus.