['Pdx1 plays a pivotal role in pancreas organogenesis and specification of some types of cells in the duodenum and antral stomach. However, its expression is not restricted to pancreas, duodenum, and antral stomach but is also found in the common bile duct during embryogenesis. This study aimed to elucidate the role of Pdx1 in the development of the common bile duct, major duodenal papilla, and duodenum.', 'Expression pattern of pdx1 during embryogenesis and the morphology of the common bile duct, major duodenal papilla, and duodenum in pdx1 null mice were analyzed.', 'The major duodenal papilla, peribiliary glands, and mucin-producing cells in the common bile duct were not formed in pdx1 null mice. Pdx1 null mice had shorter periampullary duodenal villi than wild-type mice at postnatal stages associated with reduced cell proliferation and increased apoptosis of the duodenal epithelial cells. Loss of the major duodenal papilla allowed duodeno-biliary reflux and bile infection, resulting in the formation of brown pigment biliary stones in pdx1 null mice, and antibiotics treatment significantly reduced the incidence of biliary stone formation.'] Does loss of the major duodenal papilla result in brown pigment biliary stone formation in pdx1 null mice?