UTI blockages are common in male cats due to diet alone( specifically dry kibble with non meat ingredients), pure meat eaters have a hard time digesting anything but meat. If it's totally blocked it can be fatal( sound like its urinating so good). I worked at a vet hospital in the late 80's early 90's, AFTER the blockage has been addressed you will need to change the brand of
dry kibble you feed him, as someone stated above they now make a dry kibble exclusively for this, you will need to give him a high acidic canned food daily for a couple weeks usual the liver kidney mix of chicken or beef is what the Vet would recommend, then once its better at least 2 times a week for the canned product.
good luck