A 54 year old man presents for a RUQ study due to severe sud…

A 54 year old man presents for a RUQ study due to severe sudden onset of epigastric pain, nausea and vomiting.  He has a history of cholelithiasis.  Lab tests indicate normal amylase and increased lipase.  On ultrasound, his pancreas appears enlarged but of normal echogenicity.  What is the most likely diagnosis for this patient?