The main pancreatic duct is an important duct for the excretion of pancreatic juice. The main pancreatic duct is not dilated because the diameter of the main pancreatic duct is within the normal range and the width of the pancreatic duct does not increase due to the increase of pressure in the pancreatic duct. Generally speaking, if the patient has pancreatic duct stones or pancreatic tumor lesions, the drainage of pancreatic juice will be significantly obstructed, and the accumulation of more pancreatic juice in the pancreatic duct will cause the pressure in the pancreatic duct to increase, which will manifest as dilatation of the pancreatic duct. In this case, it is often suggested that the patient has pancreatic lesions, and an enhanced CT or MRI examination of the pancreas is needed to clarify the specifics of the pancreatic lesions, and if it is a stone, surgery is needed to remove the stone from the pancreatic duct, and the patient’s prognosis is often better. However, if the patient has a dilated pancreatic duct caused by a neoplastic lesion of the pancreas, the patient’s prognosis is often poor.