What is chronic intestinal outlet obstruction?

Chronic Intestinal Outlet Obstruction

Chronic intestinal outlet obstruction is a condition characterized by failure of coordinated intestinal propulsion, causing symptoms of intestinal obstruction (colicky abdominal pain, nausea, vomiting, abdominal distension, and often dilated bowel) in the absence of a mechanical blockage, persisting for more than 6 months. 1

Types and Causes

Chronic intestinal outlet obstruction can be categorized into several types:

1. Chronic Intestinal Pseudo-Obstruction (CIPO)

• A syndrome where coordinated intestinal propulsion fails, mimicking mechanical obstruction without any actual blockage 1, 2
• Can be primary (acquired or congenital) or secondary to systemic conditions 2
• Classified based on pathology:
  • Visceral myopathy (most common in referral settings) 3
  • Visceral neuropathy 3
  • Indeterminate type

2. Defecatory Disorders

• Characterized by impaired rectal evacuation due to:
  • Inadequate rectal propulsive forces
  • Increased resistance to evacuation (anismus, dyssynergia)
  • Structural disturbances (rectocele, intussusception)
  • Reduced rectal sensation 1

3. Transit Disorders

• Normal Transit Constipation (NTC)
• Slow Transit Constipation (STC) - marked by reduced colonic propulsive activity 1
• Combination disorders - overlap of transit issues with defecatory disorders 1

Clinical Presentation

Common symptoms include:

• Colicky abdominal pain (80% of patients) 3
• Nausea and vomiting (75%) 3
• Abdominal distension 1
• Constipation (40%) or diarrhea (20%) 3
• Symptoms mimicking mechanical obstruction 2

In severe cases, malnutrition may develop (BMI <18.5 kg/m² or >10% unintentional weight loss in 3 months) 1

Diagnostic Approach

Diagnosis is based on:

1. Clinical history showing chronic or recurrent obstructive symptoms
2. Imaging showing intestinal dilation
3. Absence of mechanical obstruction 2

Key diagnostic tests include:

• Abdominal CT scan to rule out mechanical obstruction 2
• Trans-duodenal manometry of small intestine (rarely normal in CIPO) 2
• Defecating proctography and transit studies to classify constipation types 4
• Full-thickness intestinal biopsy (when available) to determine underlying pathology 1, 3

Management

Management should be directed at the main symptom, using as few drugs as possible, avoiding high doses of opioids and anticholinergic medications, and avoiding unnecessary surgery 1.

Nutritional Support

1. For malnourished patients or those at risk:
   • Start with oral supplements/dietary adjustments 1
   • If oral feeding fails but patient isn't vomiting, try gastric feeding 1
   • If gastric feeding fails, attempt jejunal feeding via nasojejunal tube 1
   • If jejunal feeding fails and malnutrition persists, parenteral nutrition may be needed 1

Symptom Management

• Pain management should avoid high-dose opioids due to risk of narcotic bowel syndrome 1
• Consider gradual supervised opioid withdrawal for patients on long-term opioids 1
• Venting gastrostomy may reduce vomiting but can have complications 1
• Prokinetic medications are rarely helpful in established cases 3

Surgical Considerations

• Nutritional status should be optimized before any surgical procedure 1
• Procedures like percutaneous endoscopic gastrostomy (PEG) or stoma creation should be delayed in severely malnourished patients 1
• Surgery is often needed for diagnosis but rarely curative 3

Prognosis and Complications

• The course is usually prolonged 3
• Quality of life is significantly impacted, requiring psychological support 3, 2
• Nutritional dependence varies:
  • Some patients maintain nutritional independence
  • Others require enteral feeding via gastrostomy/jejunostomy
  • Some need home parenteral nutrition 3
• Mortality can occur from complications like thrombosis or inflammatory conditions 3

Important Considerations

• Diagnosis is often delayed (average 5.8 years from symptom onset to first operation) 3
• Multidisciplinary care is essential, involving gastroenterologists, nutritionists, psychologists, radiologists, pathologists, and surgeons 2
• Opioid use can worsen symptoms and invalidate motility tests 1
• Distinguishing between primary dysmotility and secondary causes (medications, metabolic disorders, previous surgery) is crucial 1