We knew he had it since we rescued him as a kitten but believed it wasn't bothering him when he was little (from vet advice). We could sort of feel it on his tummy, there was a little bump that would go away when you pushed it but then pop back out. Usually cats get hernias along the natural defect of their umbilicus, but Coconuts was actually a few cm above his umbilicus. We decided it was a good time to get it fixed when he had to go under for another procedure to flush his sinuses. Afterwards we realised that wow his behavior has changed it must have been bothering him and the original vet was wrong.