Cat - blockage/urine tract infection?

You have been told correctly, complete urinary blockage is life-threatening, fatal if not treated. Hopefully your vet will catheterize the cat if he is unable to pee, and flush the crystals out of his bladder to clear the blockage. Once you get kitty home it is IMPERATIVE that you change his diet. NO MORE DRY KIBBLE. That stuff is poison. Your cat should be on canned food only, preferably a GRAIN-FREE food which is more expensive but much more healthy for the cat. Do some research!