The patient was a woman in her 70s with multiple large biliary stones. Lithotripsy was attempted after endoscopic papillary large balloon dilatation. During balloon dilation, inflator resistance, and body movement due to patient pain were observed, and maximum pressure was required for the disappearance of the balloon waist. A bile duct perforation was observed when the balloon was deflated. Computed tomography after endoscopic retrograde cholangiopancreatography showed free air from the duodenal peritoneum to the right retroperitoneum. The patient was conservatively treated with nasobiliary drainage. Endoscopic large balloon dilatation is useful for large bile duct stones that are difficult to remove using endoscopic sphincterotomy alone or endoscopic papillary balloon dilation. Perforation is a potentially fatal adverse event
therefore, imaging of the intrapancreatic bile ducts should be performed before endoscopic retrograde cholangiopancreatography and attention should be paid to the balloon dilation method.