Acute pancreatitis is a (usually sterile) inflammation with acute onset and characterized by necrosis andedema; it does not permanently disrupt the pancreatic architecture and is completely reversible. It is thoughtthat, despite the pancreatic defense mechanisms, premature activation of trypsin in the acinar cells starts acascade of reactions that result in autodigestion. Most cases are idiopathic. Dogs are often presented withgastrointestinal signs, whereas lethargy and anorexia are the most commonly observed symptoms in cats.Diagnosing pancreatitis remains a challenge, but the recent development of the pancreatic lipaseimmunoreactivity test is promising.