Hi Ron it can cause pan anywhere. If you are otherwise healthy then Crohns is the first suspect in any mysterious health issues.
I've had pan in my butt cheeks while experiencing a flare and or fistula activity.
I attributed it to nerve sensitivity radiating from the fistula. Subsided after a little bit.
As for the IBS thing I don't think it's really a disease as much as a syndrome that explains the otherwise unexplainable.
They/I could say I have IBS since I have many of the symptoms even when the Crohns is under control.
After having Crohns for awhile your colon just may not be what it should be esp. If you've had surgery.