Pathophysiology

According to some hypotheses, postoperative ileus is mediated via activation of inhibitory spinal reflex arcs. Anatomically, 3 distinct reflexes are involved: ultrashort reflexes confined to the bowel wall, short reflexes involving prevertebral ganglia and long reflexes involving the spinal cord. The long reflexes are the most significant. Spinal anaesthesia, abdominal sympathectomy, and nerve-cutting techniques have been demonstrated to either prevent or attenuate the development of ileus.

The surgical stress response leads to systemic generation of endocrine and inflammatory mediators that also promote the development of ileus. Rat models have shown that laparotomy, eventration, and bowel compression lead to increased numbers of macrophages, monocytes, dendritic cells, T cells, natural killer cells, and mast cells, as demonstrated by immunohistochemistry. Calcitonin gene-related peptide, nitric oxide, vasoactive intestinal peptide, and substance P function as inhibitory neurotransmitters in the bowel nervous system.

Nitric oxide and vasoactive intestinal peptide inhibitors and substance P receptor antagonists have been demonstrated to improve gastrointestinal function.

History

Patients with ileus typically present with vague, mild abdominal pain and bloating. They may report nausea, vomiting, and poor appetite. Abdominal cramping is usually not present. Patients may or may not continue to pass flatus and stool.

Physical examination

Patients may have distended and tympanic abdomens, depending on the degree of abdominal and bowel distension. The abdomen may be tender.

A distinguishing feature is absent or hypoactive bowel sounds unlike the high-pitched sound of obstruction. The silent abdomen of ileus reveals no discernible peristalsis or succussion splash.

Special examinations

Laboratory studies

Laboratory studies and blood work should focus on evaluations for infectious, electrolytic, and metabolic derangements.

Imaging studies

On plain abdominal radiographs, ileus appears as copious gas dilatation of both small intestine and colon.

Medical Care

Most cases of postoperative ileus resolve with watchful waiting and supportive treatment. Patients should receive intravenous hydration. For patients with vomiting and distension, use of a nasogastric tube provides symptomatic relief.

Underlying sepsis and electrolyte abnormalities, particularly hypokalemia, hyponatremia, and hypomagnesemia, may worsen ileus. These contributing conditions are easily diagnosed and corrected.

Discontinue medications that produce ileus (e.g., opiates). The use of postoperative narcotics can be diminished by supplementation with NSAID. NSAIDS may improve ileus by improving local inflammation and by decreasing the amount of narcotics used.

The presence of ileus does not preclude enteral feeding. Postpyloric tube feeding into the small bowel can be performed.

Use of prokinetic agents has had moderate success, a serotonin agonist, has reportedly been successful in treating ileus.