Daikenchuto for Intestinal Dysmotility and Prevention of Postoperative Paralytic Ielus After Pancreaticoduodenectomy

Inclusion Criteria: * Patients with periampullary tumors (extrahepatic bile duct tumor, tumors of ampulla of Vater and duodenal tumor) and pancreatic tumors (pancreatic cancer, intraductal papillary mucinous neoplasm of the pancreas, pancreatic endocrine tumor and pancreatic neuroendocrine tumor) of the head of the pancreas who are scheduled to undergo PD. * Age of at least 20 years old at the time of registration. * All patients provided written informed consent before initiation of study-related procedures. Exclusion Criteria: * Clinically problematic cardiac disease. * Liver cirrhosis or active hepatitis. * Severe pulmonary disease (interstitial pneumonia, pulmonary fibrosis, pulmonary emphysema etc.). * Chronic renal failure requiring hemodialysis. * Other malignant disease that can influence the adverse effect. * Patients with tumors requiring resection of colon. * Patients who are expected to have severe intra-abdominal adhesion due to past surgical history or past peritonitis history. * Patients who had used gastrointestinal prokinetic medication, antipsychotic medication or antidepressants. * Patients who had used Japanese herbal (Kampo) medicines within 4 weeks before registration. * Pregnant or lactating women. * Any other medical condition that makes the patient unsuitable for inclusion in the study according to the opinion of the investigator.