Mechanisms and Treatment of Postoperative Ileus

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Abstract
ILEUS IS DEFINED in Dorland's Illustrated Medical Dictionary simply as "obstruction of the intestines."1 However, the definition of postoperative ileus, the topic of this review, is a bit less clear. In 1990, Livingston and Passaro2 defined ileus as "the functional inhibition of propulsive bowel activity, irrespective of pathogenetic mechanisms." They further defined postoperative ileus as the "uncomplicated ileus occurring following surgery, resolving spontaneously within 2 to 3 days." Finally, the term paralytic postoperative ileus was defined as that form of ileus lasting more than 3 days after surgery.2 Such a distinction was necessary because different mechanisms are probably responsible for the 2 types of postoperative ileus. It may be more correct to call postoperative ileus a primary ileus in that it is most likely an inevitable response to surgical trauma. In postoperative ileus, inhibition of small-bowel motility is transient, and the stomach recovers within 24 to 48 hours, whereas colonic function takes 48 to 72 hours to return.2 Determination of the end of postoperative ileus is somewhat controversial. The studies in the literature have used varying end points, and each has its own weakness. Bowel sounds are sometimes used as an end point, but they require frequent auscultation, their presence does not necessarily indicate propulsive activity, and they can be the result of small-bowel activity and not colonic function.3 Flatus also is not the ideal end point. It requires a conscious patient who is comfortable reporting its occurrence to the investigator. Also, there is some question as to the correlation between flatus and bowel movements.4 Bowel movements are seemingly the most reliable end point, although they too may be nonspecific, representing distal bowel evacuation as opposed to global gastrointestinal tract function. In the end, the health care provider should assess the patient as a whole to determine the resolution of postoperative ileus.