Acute pancreatitis is the most serious form and the onset happens relatively suddenly.
Your dog would usually stop eating, start vomiting, diarrhea may or may not be present and there is usually a sign of lethargy, dehydration and the abdomen may appear hard-core firmer and sensitive to touch especially in the front portion of the abdomen. Pancreas is closely related to the stomach and is in the same area.
Chronic pancreatitis often presents with no symptoms. The only symptom of it is a slight elevation of pancreatic enzymes and I often see that animals on a natural diet have a naturally higher pancreatic enzyme elevation no signs of pancreatitis.
Read more at Dr. Dobias Healing Solutions: Pancreatitis in Dogs – Holistic Treatment and Prevention