Can opioids cause stenosis of the sigmoid colon?

Opioid-Induced Sigmoid Colon Stenosis

Yes, opioids can cause stenosis of the sigmoid colon through severe constipation that may progress to fecal impaction, stercoral ulceration, and in rare cases, colonic perforation. 1, 2, 3

Pathophysiology of Opioid-Induced Bowel Dysfunction

Opioids affect the gastrointestinal tract through multiple mechanisms:

• Activation of μ-opioid receptors in the small intestine and proximal colon 1
• Increased tonic non-propulsive contractions in the intestines 1
• Enhanced colonic fluid absorption leading to stool desiccation 1
• Increased minimum sensory threshold of the rectum 1
• Increased anal sphincter tone 1
• Disruption of normal peristalsis 1, 4

These effects collectively result in:

• Harder stool
• Less frequent defecation
• Less effective evacuation
• Potential fecal impaction

Progression to Stenosis and Complications

When opioid-induced constipation (OIC) is severe and prolonged, it can lead to:

1. Fecal impaction: Large mass of dry, hard stool in the rectum or proximal colon 1
2. Stercoral ulceration: Pressure necrosis of the bowel wall from impacted feces 2, 3
3. Stenosis: Narrowing of the colon lumen due to chronic inflammation and fibrosis
4. Perforation: In severe cases, stercoral perforation can occur when increased intraluminal pressure from fecaloma exceeds bowel wall perfusion pressure 2, 3

The sigmoid colon is particularly vulnerable due to:

• Its narrower diameter
• Slower transit time
• Higher water absorption in this segment

Risk Factors for Opioid-Induced Colonic Stenosis

Patients at higher risk include those with:

• Long-term opioid use 5
• History of chronic constipation 2
• Dehydration
• Immobility
• Advanced age 1
• Concurrent use of other constipating medications 1

Prevention and Management

Prevention of OIC

• Prophylactic laxative therapy: All patients receiving opioid analgesics should be prescribed concomitant laxatives unless contraindicated by pre-existing diarrhea 1
• Preferred laxatives:
  • Osmotic laxatives (polyethylene glycol, lactulose, magnesium salts) 1
  • Stimulant laxatives (senna, bisacodyl, sodium picosulfate) 1
• Avoid bulk laxatives: Psyllium is not recommended for OIC 1

Management of Established OIC

1. First-line treatment:

   • Osmotic or stimulant laxatives 1
   • Adequate hydration
   • Physical activity when possible

2. Second-line treatment:

   • Peripheral opioid antagonists (methylnaltrexone, naloxegol) for unresolved OIC 1
   • Combined opioid/naloxone medications 1

3. Management of fecal impaction:

   • Digital fragmentation and extraction of stool 1
   • Suppositories and enemas for full rectum or fecal impaction 1
   • Polyethylene glycol lavage for proximal impaction 1

Cautions

• Enemas are contraindicated in patients with neutropenia, thrombocytopenia, paralytic ileus, intestinal obstruction, recent colorectal surgery, anal/rectal trauma, severe colitis, abdominal inflammation/infection, toxic megacolon, undiagnosed abdominal pain, or recent pelvic radiotherapy 1
• Magnesium salts should be used cautiously in renal impairment 1
• Methylnaltrexone has been associated with bowel perforation in cases of Ogilvie syndrome 6

Monitoring and Follow-up

• Regular assessment of bowel function
• Adjustment of laxative regimen as needed
• Consideration of opioid rotation or dose reduction if possible
• Avoidance of medications that worsen gastric motility (anticholinergics, long-term PPIs) 7

When to Suspect Colonic Stenosis or Perforation

Urgent evaluation is needed if a patient on opioids develops:

• Severe abdominal pain
• Abdominal distension
• Signs of peritonitis
• Gastrointestinal bleeding
• Fever or sepsis
• Hypotension 2

Imaging studies (CT scan) should be performed promptly to assess for complications such as perforation, which requires emergency surgical intervention 2, 3.