Can colon cancer cause cholecystitis?

Yes, but... Colon cancer can very rarely cause obstruction of the duct draining the gall bladder(cystic duct) or liver(common bile duct) by growing directly into these structures and causing an obstruction. This can lead to cholecystitis just like that caused when the obstruction is caused by a gall stone. It is a more serious situation but i believe that I have seen it only once in my 36 year career!