A patient has severe upper abdominal pain radiating to the back after a heavy fatty meal. The pancreas sits behind the stomach (retroperitoneal), so its inflammation (pancreatitis) causes pain felt through to the back. Heavy fatty meals trigger gallbladder contraction and pancreatic enzyme release — the classic setting. The liver, just above, makes bile stored in the gallbladder; gallstones blocking the common bile duct can trigger the same attack.