Post-Operative Ileus

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Last updated: June 18, 2020
Revisions: 31

Last updated: June 18, 2020
Revisions: 31

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Post-operative ileus describes a deceleration or arrest in intestinal motility following surgery. It is classified as a functional bowel obstruction and is very common, particularly after abdominal surgery or pelvic orthopaedic surgery.

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).

Post-operative ileus has been shown to lengthen hospital stay and increased hospital costs; indeed, the overall annual expenditure in the US secondary to postoperative ileus is around $750 million to $1 billion.

*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 anastomotic leak until proven otherwise

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

A post-operative ileus is simply a delay in 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.

Common presenting features therefore are:

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

On examination, there will be abdominal distention and absent bowel sounds (whereas in mechanical obstruction there are classically ‘tinkling’ bowel sounds present)


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 routine bloods should be taken, including FBC and CRP (to check inflammatory markers), and U&Es (as fluid shifts can occur within the adynamic bowel leading to AKI). Electrolytes, including Ca2+, PO₄³⁻, and Mg2+, should also be checked and corrected accordingly

A CT scan abdomen and pelvis (often with oral contrast) will confirm the diagnosis (Fig. 1) and importantly also rule out any intra-abdominal collections or anastomotic leaks.

Figure 1 – CT scan (coronal view) showing small bowel ileus


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:

  • Nil-by-mouth (NBM), ensuring adequate maintenance intravenous fluids
    • Start a strict fluid-balance chart to monitor input-output
  • Daily bloods, including electrolytes
    • Correct any electrolyte abnormalities and monitor for acute kidney injury
  • Encourage mobilisation as tolerated
  • Reduce opiate analgesia and any other bowel mobility reducing medication

It is important to warn patients that once it does settle, they may well have very watery stool for the first 2–3 bowel movements.

Figure 2 – A nasogastric tube should be inserted as part of the management for post-operative ileus

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

Key Points

  • Post-operative ileus describes a deceleration or arrest in intestinal motility following surgery
  • Both patient and surgical factors increase the risk of it developing
  • Mainstay of management is NBM +/- NG tube, IV fluids, mobilisation, correct electrolyte abnormalities, and avoid bowel mobility reducing medication
  • CT imaging may be warranted, especially in prolonged cases, due to exclude more serious intra-abdominal pathologies as an underlying cause