Postoperative Ileus

Introduction

Ileus describes the slowing of bowel motility in the absence of mechanical obstruction.

Ileus is most commonly associated with abdominal surgery but can also occur with critical illness, non-abdominal surgery, electrolyte disturbances, opioid analgesia or anticholinergic use and comorbidities (e.g. diabetes mellitus, cardiovascular insufficiency and scleroderma).¹

Some degree of ileus is an expected and normal physiological response after surgery. However, prolonged postoperative ileus (more than four days post-surgery) is pathological and associated with significant prolongation of hospital stay.²

Aetiology

The disruption of normal bowel motility in postoperative ileus is multi-factorial due to the impact of inflammatory, hormonal and neurogenic factors following surgery.¹

Risk factors

Risk factors for postoperative ileus include:²

• Prolonged abdominal or pelvic surgery
• Lower gastrointestinal surgery
• Open surgery: associated with greater intestinal manipulation than laparoscopic
• Delayed enteral nutrition
• Intra-abdominal inflammation
• Peri-operative complications: pneumonia, intra-abdominal abscess

Clinical features

History

Typical symptoms of ileus include:

• Nausea and/or vomiting
• Abdominal distension and bloating
• Generalised mild abdominal pain
• Absolute constipation/obstipation (no flatus or stool)

Clinical examination

 Typical clinical findings on abdominal examination include:

• Abdominal distension: tympanic on percussion
• Mild diffuse abdominal tenderness
• Reduced or absent bowel sounds

Differential diagnoses

Other conditions, mainly mechanical bowel obstruction, may present very similarly to postoperative ileus. It is essential to exclude differential diagnoses which require surgical management or other interventions. 

Other possible differential diagnoses include:

• Bowel perforation
• Intra-abdominal abscess
• Pseudo-obstruction
• Acute pancreatitis
• Acute cholecystitis

Factors which should prompt a CT to exclude an alternative diagnosis include:

• Sudden, rather than insidious, onset of symptoms
• Moderate to severe abdominal pain
• Peritoneal signs: guarding or rigidity, percussion tenderness, pain on coughing, patient lying very still
• Fever and/or tachycardia

Investigations

Bedside investigations

Relevant bedside investigations include:

• Basic observations (vital signs)
• Fluid balance chart
• Stool chart

Laboratory investigations

Relevant laboratory investigations include:

• Full blood count: raised white cell count in infection
• Urea & electrolytes: vomiting may cause deranged renal function and electrolyte disturbance
• Magnesium: low magnesium worsens ileus
• Liver function tests & amylase: check for other non-surgical causes of ileus

Imaging

Postoperative ileus is primarily a clinical diagnosis.

However, if ileus has not resolved in three to four days, or if the clinical condition worsens, a CT (abdomen & pelvis with IV and oral contrast) should be performed to differentiate prolonged ileus and mechanical bowel obstruction or other intra-abdominal complications (e.g. anastomotic leak after colorectal surgery, intra-abdominal abscess).

Management

All patients with postoperative ileus should be made nil-by-mouth and be started on intravenous fluids. Fluid balance should be monitored closely.

A nasogastric (NG) tube should be inserted in patients with significant abdominal distension and vomiting who are at risk of aspiration. NG output should be monitored to guide fluid replacement.

Deranged electrolytes (including magnesium) may result from or be an exacerbating factor of ileus, so they should be checked regularly and replaced as indicated.

Using non-opioid analgesia and encouraging early mobilisation can improve bowel motility.

Once the ileus begins to resolve (i.e. there is passage of flatus or stool and improvement in abdominal distension and nausea), the patient can be restarted on a liquid diet and progress as tolerated.

In cases of prolonged ileus (over four days post-surgery) or when patients have not eaten for over five days, consider starting parenteral nutrition in consultation with a dietician.⁴

Complications

The main complication of postoperative ileus is a prolonged hospital stay.²

Other complications may include:

• Delayed wound healing: associated with poor nutrition
• Aspiration pneumonia: higher risk with vomiting or gastric distension
• Deep vein thrombosis and/or pulmonary embolism: limited mobility during hospital stay

Key points 

• Postoperative ileus is a normal physiological response to surgery
• Prolonged postoperative ileus, lasting more than four days post-surgery, is pathological
• Typical symptoms include nausea and vomiting, bloating, generalised abdominal pain and absolute constipation
• Typical signs include abdominal distension, mild diffuse abdominal tenderness and reduced or absent bowel sounds
• Postoperative ileus is primarily a clinical diagnosis, but if it is prolonged, CT of the abdomen and pelvis with IV and oral contrast should be performed to exclude other intra-abdominal pathology
• Management is mainly with supportive treatment, including bowel rest, intravenous fluids, electrolyte replacement, gastric decompression with an NG tube and reducing opioid analgesics
• Consider parenteral nutrition in patients unable to eat for five days

Reviewer

Mr Oddai Alkhazaaleh

Consultant General and Upper GI Surgeon

Editor

Dr Chris Jefferies

References 

1. BMJ Best Practice. Published in 2023. Available from: [LINK]
2. UpToDate. Postoperative Ileus. Published in 2023. Available from: [LINK]
3. Patient Info UK. Parenteral Feeding. Published in 2022. Available from: [LINK]
4. National Institute for Health and Care Excellence (NICE). Nutrition support for adults: oral nutrition support, enteral tube feeding and parenteral nutrition. Published in 2006. Available from: [LINK]