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Greek = Eileos from eilein, meaning squeeze or roll-up tight.

A condition characterised by transient impairment of bowel motility. It is considered a functional disorder of the bowel rather than owing to a mechanical cause, although sometimes the terminology is used interchangeably.

Also known as paralytic or adynamic ileus. It is most commonly seen after surgery, but there is no firm definition in terms of duration or diagnostic features as to what constitutes post-operative ileus. Surgery-associated ileus is common with intra-peritoneal surgery, but is not confined to it. Acute colonic pseudo-obstruction is sometimes considered separately.

Ileus can is also associated with electrolyte disturbances and intra-abdominal conditions such as pancreatitis, appendicitis, diverticulitis and other causes of peritonitis. Sentinel loops seen in certain intra-abdominal infections are attributed to localised segment of ileus.

Two other conditions labelled as ileus, are better considered as mechanical rather than functional disorders. These are:

  • Gallstone ileus, where a large gallstone occludes the lumen of the small bowel, or occasionally large bowel.
  • Meconium ileus, where thick secretions impede gut transit.

These are considered separately.


Clinical Features

Abdominal radiograph of patient with ileus

Post-operative Ileus

Different parts of gut variably affected. The duration of ileus is typically:

  • Stomach: 24-48 hours
  • Small intestine: 0-24 hours
  • Large intestine: 48-72 hours

The duration is also affected by anatomical site, e.g. longer in large bowel surgery. The degree of manipulation and inflammation of the tissues is also thought to contribute. A prolonged ileus is rarely directly life-threatening, but can cause significant morbidity as it delays mobilisation, resumption of nutrition and ultimately discharge.


Ileus is thought to be caused by disruption of the normal neuro-hormonal regulation of the gut. In health, various local neuronal reflexes and chemical mediators maintain gut function and motility. Putative factors that disrupt this include:


  • Inhibitory sympathetic reflexes
  • Lack of gut stimulation


  • Inflammatory mediators


  • Anaesthesia
    • ?inhalational GA agents
    • ?inhibition of sympathetic system in regional anaesthesia
  • Analgesic drugs (e.g. opiates)




One difficulty in assessing the evidence is that there is no uniform definition of what constitutes ileus, nevermind when it has resolved. Most measures of bowel function are clinical observations and are, at best, imperfect surrogate measures:

  • Flatus - indication mainly of distal bowel function.
  • Bowel sounds - implies bowel movement, but may not translate to restoration of useful motility and also does not indicate global recovery of GI function.
  • Bowel movement - reassuring, but may take several days to materialise despite satisfactory gut function.
  • Ability to tolerate oral intake - patients with ileus are often able to tolerate reasonable amounts of food and drink before nausea and distension set in.
  • Measure of electrical activity - technically too difficult for widespread use.


  • ?Prevention - see ERAS
  • Symptomatic treatment
  • Drugs may help - evidence not robust