what do I do when my dog is farting and he hasn't pooped for 2 days?

Recently my friend and his dog over for the weekend, his doggie didn't want to eat just drink water and we notice he was farting a lot and it really smelled bad so we took him out several times to poop but he didn't want to. 2 days went by and still hasn't eaten and I advised my friend to go see the doctor.