Objectives: To investigate embryology of complete and incomplete pancreas divisum (PD).
Methods: We analyzed anatomy of the pancreatic duct system in 44 cases of complete PD and 41 cases of incomplete PD. Under the concept of branch fusion between the ventral and dorsal pancreatic ducts, incomplete PD was divided into 3 types: fusion of the extreme end of the upper branch of the ventral pancreatic duct with the dorsal pancreatic duct (type 1); fusion of the lower branch of the dorsal pancreatic duct with the lower branch of the ventral pancreatic duct (type 2); and fusion of the lower branch of the dorsal pancreatic duct with the ventral pancreatic duct (type 3).
Results: Complete PD showing no ventral pancreatic duct radiologically might be induced by complete regression of the ventral pancreatic duct near the orifice in the pancreas with communication between the ventral and dorsal pancreatic ducts. Embryological mechanism of incomplete PD (type 1, n = 16; type 2, n = 10; and type 3, n = 15) was confirmed by measurement in pancreatograms.
Conclusions: Some cases of complete PD might be induced by complete regression of the ventral pancreatic duct near the orifice. Embryology of incomplete PD can be accounted by concept of branch fusion.