glad to hear you've got yourself a great vet AND a proper diagnosis
You can also try adding a little warm water to the canned food & see if that will help him to smell it better
Also you can try Tuna Water:
Whilst tuna itself is not appropriate for cats (see Which Foods to Feed), one possible compromise is to add the water in which tuna is packed to your cat's prescription or other diet in order to moisten it and make it more palatable. Tuna packed in water may actually be packed in a type of broth, which may contain onion; and other brands may contain high levels of sodium, so you need to be very sure the brand you use is acceptable. Starkist Low Sodium Tuna contains only tuna and water and is popular with Feline CRF Information listmembers in the USA.
& Yes Hepatic Lipidosis is a concern
from the same site as above
This also applies to cat who do not eat on a regular basis
If you feed a cat any fish diet exclusively, the cat can develop a condition called steatitis (yellow fat disease) http://www.vetcentric.com/reference/...ON=1&MODE=full, which is caused by a Vitamin E deficiency resulting from the imbalanced diet. Firstly the cat becomes very nervous, and then becomes hypersensitive in all the nerve endings of its skin, so it is very painful for the cat to be touched. The treatment is massive doses of vitamin E under a vet's supervision, and discontinuing any food containing vegetable oil or mineral oil because this will deplete the body's stores of vitamin E even more. Armed Forces Institute of Pathology discusses a case of steatitis in a cat - this cat was put to sleep.