Part of the TeachMe Series

Post-Operative Ileus

star star star star star
based on 23 ratings

Original Author(s): Tom Jay Grundy
Last updated: March 25, 2019
Revisions: 27

Original Author(s): Tom Jay Grundy
Last updated: March 25, 2019
Revisions: 27

format_list_bulletedContents add remove

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 anastamotic 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/ 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)


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

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+,  PO4-, and Mg2+, should also be checked and corrected accordingly

A CT scan of the abdomen and pelvis (often with oral contrast) will confirm the diagnosis (Fig. 1) and importantly also rule out any collections / anastomotic leak.


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 bloods, including electrolytes
    • Correct any electrolyte abnormalities and monitor for acute kidney injury
  • Encourage mobilisation
  • Reduce opiate analgesia and any other bowel mobility reducing medication

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

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

Cases may also warrant insertion of a nasogastric tube on free drainage (Fig. 2) and catheterising with a fluid balance chart.

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