Introduction
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.
Epidemiology
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:
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
Aetiology
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:
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
Pathophysiology
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:
Other mechanisms also exist for the formation of paralytic ileus. Opioids induce paralytic ileus by inhibiting the release of acetylcholine, subsequently reducing gastrointestinal motility.
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
Symptoms
- Bloating (60%)
- Constipation (50%)
Signs
- Abdominal swelling (60%)
Investigations
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:
Radiological investigations:
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:
Pseudo-obstruction:
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
Pseudo-obstruction:
- 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).
Management
The mainstay of treating a paralytic ileus is bowel rest and hydration.
Management of a paralytic ileus may involve the following:
Prophylactic management:
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