They really have no idea why about 60% of cats get blockages. They tried diet, fluids, many things to help Ming, my meezer. He used to block constantly but I heard that cats that get the operation have severe infections the rest of their lives and my vet doesn't like to go that far. We put Ming on amitryptiline a year ago and he hasn't had a single blockage or infection since then. They don't know why it works, but it does on most cats. Ask you vet about it. It only costs me $10 for 100 pills from Pet Meds.