Since the most common signs of pancreatitis in the cat are nonspecific; lethargy and anorexia, diagnosis can be challenging. The gold standard is a surgical biopsy of the pancreas and evaluation by a veterinary pathologist. During surgery, the pancreas is swollen and often an angry pinkish-orange color. The downside of a surgical biopsy is that it requires subjecting an ill patient to anesthesia and surgery. The biopsy will also cause more inflammation where it is performed.
Fortunately, a non-invasive test became available called feline pancreatic lipase immunoreactivity (fPLI). In a normal cat, small amounts of lipase are found in the bloodstream. The levels jump with pancreatitis. If the results are in the questionable range, I usually follow-up with an abdominal ultrasound. Either way, the cost, risk to the patient and turn around time are much reduced when compared to a surgical biopsy.
It is extremely important to diagnose pancreatitis as early in the course of the disease as possible. Left untreated, a chronic smoldering pancreatitis may destroy the pancreas leading to pancreatic insufficiency or diabetes mellitus. If your cat is ill, bring them to your veterinarian for evaluation right away. Waiting may cause permanent damage.