This is rather an uncommon malformation of pancreas but is clinically important because it may cause duodenal obstruction. In this anomaly the second part of the duodenum is surrounded by a thin, flat band of pancreatic tissue. The annular pancreas results from the growth of a bifid ventral pancreatic bud around the duodenum which fuses with the dorsal pancreatic bud to form a ring of pancreatic tissue. The annular pancreas may remain symptomless but sometimes causes obstruction of the duodenum shortly after birth or much later.