Sometimes stones are dislodged from the gallbladder and get stuck in the part of the common bile duct that merges with the pancreatic duct. This prevents pancreatic jucies from moving freely into the small intestines, which, in turn causes congestion and poor circulation in the pancreas itself. The sensations described come from the above and the resulting poor energy flow through the pancreas. Removing the stones/sludge from this area and the liver/gallbladder helps the pancreas to resume its normal functions. There is more on this in my book The Amazing Liver Cleanse (www.1stbooks.com).
With kind regards,