Post-Operative Ileus

Post-operative ileus describes a deceleration or arrest in intestinal motility following surgery. It is classified as a functional obstruction of the bowel. It is a common phenomenon, with many surgical patients having a degree of physiological ileus post-operatively.

Remember however that although innocent in the majority of patients, it can be a sign of other intra-abdominal pathology, in particular a collection or anastomotic leak (as pus or faeces will irritate the bowel and often cause it cease functioning).

Note: It is important to appreciate that any patient with a bowel obstruction picture who fails to progress as expected after a bowel resection has an anastamotic leak until proven otherwise.

Post-operative ileus has been shown to lengthen hospital stay and increased hospital costs. Previous studies have estimated that an average of 8 days in added on to a hospital stay with post-operative ileus and the overall annual expenditure secondary to postoperative ileus is around $750 million to $1 billion in the US.

Risk Factors

  • Patient Factors
    • Increased age
    • Electrolyte derangement (e.g. Na+, K+ and Ca2+ derangement)
    • Neurological disorders (e.g. Dementia or Parkinson’s Disease)
    • Use of anti-cholinergic medication
  • Surgical Factors
    • Use of opioid medication
    • Pelvic surgery
    • Extensive intra-operative intestinal handling
    • Peritoneal contamination (by free pus or faeces)
    • Intestinal resection

Clinical Features

Patients with a post-operative ileus will present with:

  • Failure to pass flatus or faeces
  • Sensation of bloating and distention
  • Nausea and vomiting / high NG output

On examination, there will be abdominal distention and absent bowel sounds; importantly, this is a key difference to the presentation of a mechanical obstruction (which typically has ‘tinkling’ bowel sounds present)

A post-operative ileus will delay to the return of normal bowel function. As a result, the symptoms of post-operative ileus may be the same as those of a mechanical obstruction.


In the patients with suspected post-operative ileus, the aim of the investigations are to rule out more serious pathologies and determine any underlying cause.

Initial Investigations


  • U&Es and calcium levels
    • Na+, K+ and Ca2+ abnormalities may cause paralytic ileus
  • Inflammatory markers (WCC, CRP) to look for intra-abdominal collections or leaks

An abdominal X-ray (AXR) can also be requested, which may demonstrate small or large bowel dilatation.

Further Investigations

A CT scan (often with oral contrast) will confirm diagnosis and rule out any collections / anastomotic leak. This is only really useful 3-5 days after surgery.


As long as serious pathology (e.g. anastomotic leak) has been excluded, the management of post-operative ileus is conservative. Any established postoperative ileus should be initially managed with:

  • Daily U&Es
    • Correct electrolyte abnormalities present and monitor for acute kidney injury (AKI)
  • Fig 2 - A nasogastric tube should be inserted as part of management of post-operative ileus.

    Figure 1 – A nasogastric tube should be inserted as part of the initial management of post-operative ileus.

    Encourage mobilisation

  • Reduce opiate analgesia and any other bowel mobility reducing medication

It is important to warn patients that once it does settle, they will get very watery diarrhoea for the first 2 – 3 bowel movements.

Prolonged cases may warrant insertion of a nasogastric (NG) tube on free drainage and catheterising with a fluid balance chart started.

Prophylactic Measures

To reduce the risk of developing post-operative ileus, preventive steps include:

  • Minimise intra-operative intestinal handling
  • Avoid fluid overload (causing intestinal oedema)
  • Minimise opiate use
  • Encourage early mobilisation

Gum chewing as part of post-operative recovery following open GI surgery has been shown in a meta-analysis to reduce the period of post-operative ileus, as has enhanced recovery programs.


Question 1 / 5
Which of the following is NOT a patient factor for post-operative ileus?


Question 2 / 5
Which type of medication increases the likelihood of post-operative ileus?


Question 3 / 5
Which of the following is NOT a sign of post-operative ileus?


Question 4 / 5
What blood test would be performed to assess if there is an electrolyte abnormality?


Question 5 / 5
Which of the following is NOT a prophylactic measure to reduce the chance of post-operative ileus?


Further Reading

Postoperative ileus following major colorectal surgery
Chapman SJ et al., British Journal of Surgery

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