How do you differentiate and manage ileus versus bowel obstruction?

Differentiating and Managing Ileus versus Bowel Obstruction

The key difference between ileus and bowel obstruction is that ileus is a functional disorder without mechanical blockage, while bowel obstruction involves a physical blockage of the intestinal lumen requiring different management approaches. 1

Clinical Differentiation

Ileus (Functional/Paralytic)

• Characterized by diffuse gastrointestinal dysmotility without physical blockage 2
• Often occurs after abdominal surgery, with medications affecting peristalsis, or due to metabolic disorders 1, 3
• Typically presents with more generalized, less colicky abdominal pain 1
• Bowel sounds are typically diminished or absent 4
• Nausea and vomiting may be present but less prominent than in mechanical obstruction 1
• Abdominal distension is often more diffuse 1

Mechanical Bowel Obstruction

• Involves physical blockage of intestinal lumen by adhesions (55-75% of small bowel obstructions), hernias (15-25%), or tumors (5-10%) 1
• Pain is typically colicky and intermittent due to increased motility trying to overcome the blockage 1
• Bowel sounds may be hyperactive, high-pitched, or tinkling 1
• Nausea and vomiting are more prominent, especially in proximal obstructions 1
• Abdominal distension with positive likelihood ratio of 16.8 1
• Previous abdominal surgery has 85% sensitivity and 78% specificity for predicting adhesive small bowel obstruction 1

Diagnostic Approach

History and Physical Examination

• Assess for previous abdominal surgery, hernias, cancer history, inflammatory bowel disease 1
• Examine all hernia orifices (umbilical, inguinal, femoral) and surgical scars 1
• Evaluate for peritoneal signs suggesting strangulation or perforation 1
• Digital rectal examination to detect masses or blood 1

Laboratory Tests

• Complete blood count, electrolytes, renal function, liver function tests 1
• Elevated white blood cell count, lactic acid, and low serum bicarbonate may indicate intestinal ischemia 1

Imaging

• Abdominal X-ray: First-line imaging with 74% sensitivity for bowel obstruction 1

  • Small bowel obstruction: dilated small bowel loops >3cm with air-fluid levels 1
  • Large bowel obstruction: dilated colon >6cm 1
  • Ileus: diffuse bowel dilation including colon 4, 3

• CT scan with IV contrast: Preferred imaging for suspected bowel obstruction 1, 5

  • 90% diagnostic accuracy for bowel obstruction 1
  • Can identify transition point, cause, and complications like ischemia 1
  • Can differentiate between mechanical obstruction and ileus 1

• Water-soluble contrast studies: Both diagnostic and therapeutic 1

  • If contrast reaches colon within 24 hours, predicts successful non-operative management 1

Management

Ileus Management

• Supportive care with bowel rest (nil per os) 1, 3
• Nasogastric tube decompression to prevent aspiration and reduce distension 1, 3
• Intravenous fluid resuscitation and electrolyte correction 1, 3
• Discontinue medications that inhibit bowel motility (opioids, anticholinergics) 1, 3
• Consider prokinetic agents like metoclopramide 1
• For colonic pseudo-obstruction with significant distension, neostigmine may be effective 3
• Colonoscopic decompression may be needed for acute colonic pseudo-obstruction with severe distension 3

Mechanical Bowel Obstruction Management

• Initial non-operative management for most cases without signs of peritonitis, strangulation, or ischemia 1, 5

  • Nil per os 1
  • Nasogastric tube decompression 1
  • Intravenous fluid resuscitation 1
  • Electrolyte correction 1
  • Water-soluble contrast administration (both diagnostic and therapeutic) 1

• Indications for urgent surgical intervention: 1, 5

  • Signs of peritonitis
  • Evidence of bowel ischemia or strangulation
  • Complete obstruction with failure to progress after 72 hours of conservative management
  • CT findings of closed-loop obstruction

• Surgical approach: 1

  • Laparotomy with adhesiolysis for adhesive small bowel obstruction
  • Hernia repair for incarcerated hernias
  • Resection and anastomosis for tumors or ischemic segments
  • Laparoscopic approach may be considered in selected cases

Complications and Monitoring

• Monitor for signs of dehydration, electrolyte imbalances, and renal dysfunction 1
• Watch for development of abdominal compartment syndrome with increased intra-abdominal pressure 2
• Risk of recurrence: 12% within 1 year and 20% within 5 years after non-operative management of adhesive small bowel obstruction 1
• Regular reassessment of clinical status, abdominal examination, and vital signs 1

Special Considerations

• Partial vs. complete obstruction: Partial obstructions are more likely to resolve with non-operative management 1
• Strangulation risk increases with duration of obstruction 1
• Elderly patients have higher morbidity and mortality with delayed diagnosis 1
• Pregnancy requires modified imaging approach (ultrasound and MRI preferred over CT) 1