a 22-year-old law student comes to the office complaining of severe abdominal pain radiating to his back. he states it began last night after hours of heavy drinking. he has had abdominal pain and vomiting in the past after drinking but never as bad as this. he cannot keep any food or water down, and these symptoms have been going on for almost 12 hours. he has had no recent illnesses or injuries. his past medical history is unremarkable. he denies smoking or using illegal drugs, but admits to drinking 6 to 10 beers per weekend night. he admits that last night he drank around 14 drinks. examination shows a young man appearing his stated age in some distress. he is leaning over on the examination table and holding his abdomen with his arms. his blood pressure is 90/60 and his pulse is 120. he is afebrile. his abdominal examination reveals normal bowel sounds, but he is very tender in the left upper quadrant and epigastric area. he has no murphy's sign or tenderness in the right lower quadrant. the remainder of his abdominal examination is normal. his rectal, prostate, penile, and testicular examinations are normal. he has no inguinal hernias or tenderness with that examination. blood work is pending. what etiology of abdominal pain is most likely causing his symptoms?