Ileus pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

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Pathophysiology

• Ileus is defined as temporary cessation of intestinal peristalsis in the absence of mechanical obstruction. The pathogenesis of ileus is multifactorial. Intestinal peristalsis is primarily regulated by autonomic and central nervous system. However, certain medications and metabolism products may also alter the normal intestinal equilibrium leading to temporary dysfunction in intestinal movements. With increasing time, intestinal aperistalsis results in accumulation of air and fluid in the bowel lumen.
• The most common cause of ileus is abdominal surgery.
  • In fact, post-operative ileus is so common that it is sometimes regarded as a normal sequelae of surgery.
  • Post-operative ileus lasting longer than 3 days is termed as paralytic ileus.
  • The risk of postoperative ileus depends upon the type of surgery; with the highest risk associated with colorectal surgery.

• The most common cause of ileus are the drugs that affect intestinal motility and a history of previous abdominal surgery.
  • Drugs affecting intestinal motility primarily includes antimotility agents and other drugs such as opiates, vincristine.
  • Abdominal conditions such as gastroenteritis and peritonitis may also affect the intestinal motility leading to ileus.
  • Electrolyte abnormalities such as hypokalemia, hypercalcemia, hypermagnesemia, acidosis

• Inhibitory neural reflexes
• Inflammation: Ileus may increase adhesion formation, because intestinal segments have more prolonged contact, allowing fibrous adhesions to form, and intestinal distention causes serosal injury and ischemia. Intestinal distention has been shown to cause adhesions in foals. In a recent survey of ACVS diplomates on drugs to prevent ileus and therefore prevent adhesions. The drug used in this survey was lidocaine, erythromycin, and cisapride. Some respondents also mentioned the importance of walking horses postoperatively to stimulate motility. Repeat celiotomy to decompress chronically distended small intestine and remove fibrinous adhesions is also a useful method of treating ileus and reducing adhesions, and it has been associated with a good outcome.
• Neurohumoral peptides