Tolerance of an enteral diet is one of the fundamental components of postoperative wellness, along with the ability to mobilize freely without supplemental oxygen and a readiness to be discharged home as soon as possible. Accordingly, postoperative gastrointestinal (GI) tract dysfunction is best defined as intolerance of an enteral diet after having been tolerant of one preoperatively. I prefer the term postoperative GI tract dysfunction over postoperative ileus , as ileus is ill defined, covering a wide spectrum of clinical signs and having a range of published incidences so broad (5%–100%) that it defies useful discussion.
GI DYSFUNCTION: A COMMON POSTOPERATIVE MORBIDITY
Postoperative GI tract dysfunction is common, as illustrated by a large prospective cohort study at Duke University Medical Center 3 that used the Postoperative Morbidity Survey (which has since been validated 4) to document complications following major noncardiac surgery (ie, anticipated duration > 2 hours and anticipated blood loss > 500 mL). Hospital discharge was delayed in 27% of the study’s 438 patients as a result of a postoperative complication, and GI dysfunction was the most common type of complication overall and on postoperative days 5, 8, and 15. Episodes of GI dysfunction ranged from intolerance of an enteral diet to ischemic gut resulting in multiple organ failure. 3
A MULTIFACTORIAL PATHOGENESIS
The pathophysiology of postoperative GI tract dysfunction can be ischemic, metabolic, toxic, neurogenic, myogenic, pharmacologic, or mechanical.
It is important to recognize that in many cases no single factor explains the whole story behind postsurgical GI tract dysfunction, and none of these factors is an ipso facto cause of such dysfunction. For instance, a “mechanical” pathogenesis refers to any manipulation of the gut that causes an inflammatory response in the gut’s various layers, resulting in injury. 5,6 However, GI tract dysfunction commonly occurs after operations (including laparoscopic procedures) in which the gut was not handled at all. Similarly, in terms of a pharmacologic pathophysiology, while opioids can affect GI propulsion and cause constipation, 7,8 avoidance of opioid use does not ensure prevention of GI tract dysfunction. Moreover, opioid abusers do not generally exhibit intolerance of enteral nutrition.