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Ileus is a functional, non-mechanical inhibition of coordinated gastrointestinal activity that frequently occurs after abdominal surgery. Its pathogenesis is multifactorial in nature, with disturbances in inflammatory, neurologic, immunologic, electrolyte and receptor-mediated functioning.
The occurrence of this condition has consequences for patient and hospital alike. Ileus slows patient recovery, thereby prolonging hospital stay, and is associated with an increased number of diverse complications (namely thrombotic or infectious in nature). In addition, prolonged hospital stay often has a negative psychological impact on a patient, creating an additional barrier for adequate postoperative recovery.
Primary features of postoperative or paralytic ileus include nausea and vomiting, inability to tolerate oral intake of food, abdominal distension, as well as the delayed passage of flatus and stool. The wall of the gut can become congested and edematous, and a significant amount of fluid can be secreted into the bowel lumen. That can in turn cause dehydration and significant electrolyte imbalance.
On examination, the patient can be severely dehydrated, which results in hypotension, tachycardia and the loss of skin turgor. The distended abdomen is often tympanic. Unlike mechanical obstruction where peristalsis may be visible and bowel sounds increased, in postoperative and paralytic ileus both of these signs are absent. Rectal examination usually shows an empty rectum.
The terminology used to describe postoperative ileus falls into two distinct classifications. Postoperative ileus is defined as the obligatory period of gastrointestinal dysfunction that occurs instantly after surgery, with resolution signaled by passage of stool or flatus and tolerance of oral intake.
On the other hand, prolonged postoperative ileus should have at least two of the following five signs: nausea or vomiting, inability to tolerate oral intake 24 hours after surgery, absence of flatus 24 hours after surgery, abdominal distension and radiologic evidence of bowel distension without mechanical obstruction.
Initial examinations of ileus should encompass full blood count and other laboratory tests. The hemoglobin and hematocrit may be raised due to the hemoconcentration, which is often a consequence of dehydration. In addition, the white cell count is sometimes elevated. Electrolyte disturbances are often found, depending on the severity of the condition, hence raised urea and creatinine indicate renal impairment.
The plain abdominal film will show copious gas dilatation of large and small bowels. An erect chest film is necessary in order to exclude perforation, which is apparent as free air beneath a raised hemi-diaphragm. In patients with risk factors for gastroparesis, a gastric emptying study is sometimes considered.
In postoperative patients, a computerized tomography (CT) is performed if the presumed ileus has not resolved in one week, or the clinical condition of the patient is getting worse. Such imaging of the abdomen may be performed with intravenous and oral water-soluble contrast. In the immediate postoperative period, computerized tomography with an oral contrast represents a method of choice in distinguishing prolonged ileus from mechanical obstruction.