What is a large bowel obstruction?

Large Bowel Obstruction

Large bowel obstruction is a serious and potentially life-threatening surgical emergency characterized by a mechanical blockage of the colon or rectum, most commonly caused by colorectal cancer (60%), volvulus (15-20%), or diverticular disease (10%). 1, 2

Etiology and Pathophysiology

Large bowel obstruction differs from small bowel obstruction in several key ways:

• Primary causes:

  • Colorectal cancer (60%)
  • Volvulus (15-20%)
  • Diverticular disease (10%)
  • Other causes (10%): carcinomatosis, endometriosis, inflammatory bowel disease stenosis, intussusception, ischemic stenosis, radiation stenosis, post-anastomotic stenosis 1

• Pathophysiological changes:

  • Increased intraluminal pressure proximal to obstruction
  • Colonic distension with potential for ischemia and perforation
  • Bacterial overgrowth and translocation
  • Fluid and electrolyte imbalances 1

Clinical Presentation

• Abdominal pain: Typically colicky in nature due to increased peristalsis attempting to overcome the obstruction
• Abdominal distension: A strong predictive sign with a positive likelihood ratio of 16.8
• Altered bowel habits: Constipation or obstipation (inability to pass stool or gas)
• Nausea and vomiting: Less prominent and occurs later than in small bowel obstruction
• Rectal bleeding: May suggest colorectal malignancy
• Severe pain unresponsive to analgesics: May indicate ischemia or perforation 1, 3

Diagnostic Approach

1. Laboratory studies:

   • Complete blood count
   • Renal function and electrolytes
   • Liver function tests
   • Serum bicarbonate, arterial pH, and lactate (to assess for ischemia)
   • Coagulation profile 1, 3

2. Imaging:

   • Abdominal X-ray: First-line imaging with 84% sensitivity and 72% specificity for large bowel obstruction
   • CT scan with IV contrast: Gold standard with higher sensitivity and specificity, can identify location, cause, and complications
   • Water-soluble contrast enema: 96% sensitivity and 98% specificity 1, 3

3. Endoscopy:

   • May be both diagnostic and therapeutic, especially in cases of volvulus or pseudo-obstruction 3

Management

Initial Management

• Fluid resuscitation: Isotonic crystalloids to correct fluid and electrolyte imbalances
• Nasogastric decompression: To prevent aspiration and reduce vomiting
• Foley catheter: For monitoring urine output
• Broad-spectrum antibiotics: If signs of infection, ischemia, or perforation are present 1, 3

Definitive Management

Management depends on the cause, location, and severity of obstruction:

1. Right-sided obstruction:

   • Extended right colectomy with terminal ileostomy or primary anastomosis 3

2. Left-sided obstruction:

   • Hartmann's procedure (resection with end colostomy)
   • Resection with on-table irrigation and primary anastomosis
   • Self-expanding metal stents (SEMS) as bridge to surgery or palliative measure in malignant obstruction 3

3. Volvulus:

   • Sigmoid volvulus: Endoscopic decompression followed by elective resection
   • Cecal volvulus: Usually requires surgical intervention 3, 4

4. Pseudo-obstruction:

   • Conservative management with correction of underlying causes
   • Neostigmine for acute colonic pseudo-obstruction
   • Endoscopic decompression if conservative measures fail 3, 4

Complications and Prognosis

• Complications:

  • Perforation
  • Peritonitis
  • Sepsis
  • Ischemia
  • Electrolyte imbalances

• Prognosis:

  • Mortality rates vary based on cause, patient factors, and timing of intervention
  • Prompt intervention (within 2 days) results in decreased length of stay and greater likelihood of discharge to home 5
  • Recurrence rates after surgical management are approximately 8% at 1 year and 16% at 5 years 3

Special Considerations

• Elderly patients: Higher risk of complications and may have atypical presentations
• Pregnant women: Higher failure rate of non-operative treatment with risk of fetal loss
• Comorbidities: May influence management decisions and increase surgical risk 1, 3

Prevention of Recurrence

• For adhesion-related obstructions:

  • Adhesion barriers like Icodextrin 4% or Hyaluronate-carboxymethylcellulose during surgery
  • Minimally invasive surgical techniques when appropriate 3

• For malignant obstructions:

  • Appropriate cancer surveillance and follow-up
  • Early detection and treatment of recurrent disease 3