Pancreatitis causes severe pain as u said.similarly gall bladder spasm or persistant contraction due to the presence of stones causes unpleasant severe pain.outflow channel of liver ,the common bile duct and the outflow channel of pancreas,the pancreatic duct joins together to enter the intestine.when gall bladder contain small ,multiple stones,during contaction it slips in to the liver outflow track ,the bile duct and finally it reaches the common channel.these stones can slip in to the pancreatic duct . and it can block the pacreatic juice flowing through the duct and finally results in to gall stone induced acute pancreatitis once gall bladder is taken out this complication never occur due to a gall bladder disease .there are several other causes of pancreatitis like acoholism, viral infetctions,etc once the gall bladder is taken out,you dont have to restrict your food.you can eat anything including oily food which is contraindicated in gall stone disease