Your problems with Oliver sound like they're diet-related. If you want to avoid these problems in the future, you might try a raw meat diet - we have seen diabetes cured by feeding a species-appropriate diet of raw meat, and many other types of illnesses can be avoided if you feed this way.

A cat is not a natural water-drinker, and usually only drinks water when VERY thirsty, in order to re-hydrate a kibble diet. My advice - NEVER FEED A KIBBLE DIET - Cats should not be fed dry food, and there are many reasons for this, including the grain content of the diet, which is a big problem for cats.

Of course, you vet may not agree, as vets are trained in their nutritional knowledge, by commercial pet food companies.

If you want more info, let me know.

All the Best,
Gayle