So, we talking the external rectal pain caused by irritation from the excessive diarrhea, and wiping? or is it that internal rectal pain..the burning way up high? for external, yea the lidocaine would be good. or have you tried any barrier methods such as what is used for diaper rashes, like desitin? or A&D ointment?
for the internal rectal pain, the only thing that worked for me was good ol PERCOCET!