Postoperative ileus: mechanisms and future directions for research.

Postoperative ileus (POI) is an abnormal pattern of gastrointestinal motility characterized by nausea, vomiting, abdominal distension and/or delayed passage of flatus or stool, which may occur following surgery. Postoperative ileus slows recovery, increases the risk of developing postoperative complications and confers a significant financial load on healthcare institutions. The aim of the present review is to provide a succinct overview of the clinical features and pathophysiological mechanisms of POI, with final comment on selected directions for future research.Terminology used when describing POI is inconsistent, with little differentiation made between the obligatory period of gut dysfunction seen after surgery ('normal POI') and the more clinically and pathologically significant entity of a 'prolonged POI'. Both normal and prolonged POI represent a fundamentally similar pathophysiological phenomenon. The aetiology of POI is postulated to be multifactorial, with principal mediators being inflammatory cell activation, autonomic dysfunction (both primarily and as part of the surgical stress response), agonism at gut opioid receptors, modulation of gastrointestinal hormone activity and electrolyte derangements. A final common pathway for these effectors is impaired contractility and motility and gut wall oedema. There are many potential directions for future research. In particular, there remains scope to accurately characterize the gastrointestinal dysfunction that underscores an ileus, development of an accurate risk stratification tool will facilitate early implementation of preventive measures and clinical appraisal of novel therapeutic strategies that target individual pathways in the pathogenesis of ileus warrant further investigation.