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).

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.

*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

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 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.


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 bloods should be taken, including FBC and CRP (to assess for intra-abdominal collections or leaks as a potential underlying cause), and U&Es and calcium levels (electrolyte abnormalities can cause paralytic ileus)

A CT scan (often with oral contrast) will confirm the diagnosis (Fig. 1) and importantly also 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 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

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

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

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

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.

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


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

Non-steroidal anti-inflammatory drugs reduce the time to recovery of gut function after elective colorectal surgery: a systematic review and meta-analysis
Milne TG et al., Colorectal Disease

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