Often referred to as a postoperative ileus, a paralytic ileus is a common consequence of abdominal surgery. It occurs due to reduced motility of the gastrointestinal tract, secondary to a failure of peristalsis. Failure occurs due to (either full or partial) paralysis of the intestinal muscles which subsequently leads to a functional bowel obstruction. In most cases, it resolves within 2-7 days with conservative management and correction of any underlying/contributory causes such as electrolyte abnormalities.


Paralytic ileus is a condition most commonly seen in patients following abdominal surgery. Reported rates for postoperative ileus range between 10-30%. Literature suggests the incidence of paralytic ileus post colorectal surgery is as high as 17.4%. Incidence of paralytic ileus is reduced with laparoscopic surgery as opposed to open surgery.

Risk factors for paralytic ileus include:
  • Sex - male sex has been shown to be a significant risk factor for a paralytic ileus - in a study of 17,876 cases of colectomy, 54.1% of males developed a paralytic ileus vs. 50.3% of females (p<0.001)
  • Increasing age - incidence of paralytic ileus increase with age
  • Electrolyte imbalance, particularly those involving potassium and calcium
  • History of intestinal injury or trauma
  • History of GI disease e.g. Crohn's disease and diverticulitis
  • Sepsis
  • Previous radiation (radiotherapy) to the abdomen


A paralytic ileus occurs secondary to physiological stress, including surgery, sepsis, metabolic abnormalities, and gastrointestinal diseases.

The most common cause of a paralytic ileus is abdominal surgery. Literature suggests the incidence of paralytic ileus post colorectal surgery is as high as 17.4%. The risk of a post-operative ileus may be reduced by limiting the amount of bowel handling during the procedure.

Other causes include:
  • Electrolyte/metabolic abnormalities
    • Hypokalaemia, hyponatraemia, uraemia, severe hypothyroidism, diabetic ketoacidosis.
  • Peritonitis
  • Trauma
  • Drugs
    • Tricyclics antidepressants, anti-cholinergics, opioids
  • Neurological
    • Stroke, spinal surgery, spinal cord injury


The pathophysiology for a paralytic ileus is multifactorial, involving both autonomic nervous and hormonal mechanisms.

The most common causes of a paralytic ileus, abdominal surgery, is caused by the trauma of mechanical handling of the bowel. The pro-inflammatory cascade of events within intestinal tissues of postoperative ileus is as follows:
  • Bowel trauma (through manipulation) activates latent macrophages
  • Activated macrophages then increases production of nitric oxide, inflammatory cytokines and prostaglandins via the cyclo-oxygenase-2 pathway
  • Leukocytes are then recruited to the bowel wall
  • Subsequently, peristalsis is inhibited and a paralytic ileus occurs

Other mechanisms also exist for the formation of paralytic ileus. Opioids induce paralytic ileus by inhibiting the release of acetylcholine, subsequently reducing gastrointestinal motility.

Clinical features



In cases where a paralytic ileus is suspected and not responding to conservative management, a combination of clinical judgement and imaging investigations should be used to investigate further to exclude more serious pathologies.

Bedside investigations:
  • Blood tests
    • Blood glucose
    • FBC and CRP - to check inflammatory markers
    • U&E including magnesium, phosphate and calcium - to check electrolytes

Radiological investigations:
  • CT scanning
    • The gold standard
    • Often a distinct transition point can be seen where bowel calibre changes from normal to abnormal
    • Dilated bowel loops proximal to the transition point (small bowel >3.0 cm, large bowel >5 cm)
  • Abdominal X-Ray
    • Sensitivity is 50-60%, therefore less preferable to CT scanning
    • Features of bowel obstruction - either small bowel, large bowel or both
  • Ultrasound scanning
    • Not routinely used in adults at present but has been shown to reliably exclude the condition in up to 89% of patients
    • Commonly used in a paediatric setting

Differential diagnosis

The two most common differentials for paralytic ileus are pseudo-obstruction (AKA Ogilvie syndrome) and mechanical bowel obstruction. These are less likely to occur immediately post surgery than a paralytic ileus. The typical time course of a paralytic ileus is 48-72 hours post operatively.

Mechanical bowel obstruction:
  • May be caused by adhesions, volvulus, hernias, intussusception, foreign bodies or neoplasms
  • Similar to paralytic ileus, it may present with abdominal pain, constipation, nausea and vomiting
  • In contrast to paralytic ileus, auscultation may reveal high-pitched, tinkling sounds unlike the absent bowel sounds of paralytic ileus. A mechanical bowel obstruction is also more likely to show a definitive transition point on CT imaging and show definitive air fluid levels

  • Acute distension of the colon
  • Similarly to paralytic ileus, electrolyte abnormalities, trauma, drugs and sepsis may contribute to its occurrence
  • In contrast to paralytic ileus, pseudo-obstruction effects only the large bowel and does not involve the small bowel, as can be seen on imaging (Abdominal X-Ray).


The mainstay of treating a paralytic ileus is bowel rest and hydration.

Management of a paralytic ileus may involve the following:
  • Intravenous fluid and bowel rest (nil by mouth) initially. Sips of clear fluid for comfort may be permitted
  • A nasogastric tube on free drainage
  • Avoidance of opioid analgesia
  • Correction of the underlying cause e.g. electrolyte abnormalities
  • Discontinue medications known to cause ileus
  • Mobilisation

Prophylactic management:
  • Enhanced recovery after surgery pathways are increasingly being utilised in an attempt to expedite the recovery of intestinal function
  • Such pathways involve minimising opioid analgesia, chewing gum, laparoscopic surgery and early post operative mobilisation