What is an ileus?

Ileus: Definition and Clinical Implications

An ileus is a functional bowel obstruction characterized by the failure of intestinal contents to progress through the gastrointestinal tract in the absence of a mechanical obstruction, resulting from impaired intestinal motility or propulsion. 1

Types and Pathophysiology

Ileus can be classified into two main categories:

1. Adynamic or Paralytic Ileus:

   • Characterized by decreased or absent intestinal peristalsis
   • Results in intestinal dilatation, increased luminal pressure, and potential gut wall ischemia 2
   • Most common form of ileus encountered clinically

2. Mechanical Ileus (for comparison):

   • Caused by physical blockage of the intestinal lumen
   • Different etiology but can present with similar symptoms

Causes

Common causes of adynamic ileus include:

• Post-surgical: Most common setting, especially after abdominal operations
• Metabolic disturbances: Electrolyte abnormalities (particularly hypokalemia, hypomagnesemia)
• Medications: Opioids, anticholinergics, calcium channel blockers
• Inflammatory conditions: Peritonitis, pancreatitis, appendicitis
• Neurological disorders: Spinal cord injuries, autonomic neuropathy
• Systemic illness: Sepsis, pneumonia, uremia 3, 4

Clinical Presentation

Typical signs and symptoms include:

• Abdominal distension
• Nausea and vomiting
• Absence of bowel movements or flatus
• Diffuse, mild abdominal pain
• Decreased or absent bowel sounds on examination
• Tympanic percussion of the abdomen 1, 5

Diagnostic Approach

1. Imaging:

   • Plain abdominal radiographs: Show dilated bowel loops with air-fluid levels
   • CT scan: Gold standard to differentiate between mechanical obstruction and ileus
   • Look for: Dilated bowel without a transition point (unlike mechanical obstruction) 1

2. Laboratory tests:

   • Complete blood count: To assess for leukocytosis
   • Electrolytes: To identify metabolic disturbances
   • Renal and liver function tests 3

Management

Treatment is primarily supportive and focuses on addressing the underlying cause:

1. Fluid and Electrolyte Management:

   • Isotonic fluids (0.9% normal saline or lactated Ringer's) for volume replacement
   • Correction of electrolyte abnormalities 3

2. Bowel Rest and Decompression:

   • Nasogastric tube placement for gastric decompression
   • NPO (nothing by mouth) status until resolution 3, 4

3. Medication Management:

   • Discontinue medications that decrease intestinal motility (especially opioids)
   • Consider prokinetic agents in selected cases 3, 4

4. Mobilization:

   • Early and regular mobilization to stimulate bowel function 3

5. Nutritional Support:

   • For prolonged ileus (>7 days), consider enteral nutrition via nasojejunal tube
   • Parenteral nutrition if enteral feeding fails or is contraindicated 3

Complications

If not properly managed, ileus can lead to:

• Bacterial overgrowth and translocation
• Systemic inflammatory response syndrome
• Increased intra-abdominal pressure
• Abdominal compartment syndrome (in severe cases)
• Aspiration pneumonia
• Malnutrition and prolonged hospitalization 3, 2

Special Considerations

Pregnancy

Colonic volvulus is a leading cause of bowel obstruction in pregnant women, with diagnosis and treatment complicated by the pregnancy. Maternal and fetal prognosis worsens with delayed diagnosis 1.

Monitoring

Regular assessment of:

• Abdominal distention
• Bowel sounds
• Passage of flatus/stool
• Fluid balance
• Intra-abdominal pressure if abdominal compartment syndrome is suspected 3

Historical Context

Interestingly, the term "ileus" has evolved significantly over time. Originally derived from the Greek word for "twisted," it initially referred to what we now call sigmoid volvulus. Over centuries, its meaning has shifted from describing specific mechanical obstructions to its current usage denoting functional, non-mechanical obstruction 6.

Prevention

Preventive measures include:

• Minimizing opioid use
• Early mobilization after surgery
• Maintaining fluid and electrolyte balance
• Proper pain management with non-opioid alternatives when possible 3