Most stones in the bile ducts can be removed during ERCP. During this procedure, doctors pass an instrument through the endoscope to trap and then pull the stone out of the duct. Gallstones cannot be removed using this technique. Most people who have had ERCP and endoscopic sphincterotomy later have their gall bladder surgery, typically using a laparoscope. If the gallbladder remains, stones in the gallbladder may pass into the ducts, causing repeated blockages.