Pancreatitis can occur in any cat, but some breeds are more susceptible to the disease than others, including the Siamese. Additionally, pancreatitis is more common in middle-aged and older cats. Symptoms. Cats instinctually hide the fact that they are sick, and cats with pancreatitis are no exception. Typically, they have vague signs, especially as compared to dogs, so it is not obvious they are sick. If your cat has pancreatitis, you might observe the following: 1  Lethargy (common). 2  Dehydration (common). 3  Decrease in appetite (common). 4  Weight loss (common). 5  Vomiting (less common). 6  Diarrhea (less common). 7  Abdominal pain (difficult to asses, assume present). 8  Signs of fever (less common).