What is adhesive intestinal obstruction?

Adhesive Intestinal Obstruction: Definition and Clinical Entity

Adhesive intestinal obstruction (also called adhesive small bowel obstruction or ASBO) is a surgical emergency where fibrous tissue bands connecting normally separated peritoneal surfaces physically block the small intestine, preventing passage of intestinal contents. 1

Pathophysiology

Peritoneal adhesions are abnormal fibrous tissue connections between organs or surfaces within the abdominal cavity that should normally be separated. 1 These represent a pathological healing response of the peritoneum following injury, rather than normal tissue repair. 1

Primary Causes of Adhesion Formation

• Previous abdominal surgery is the most common cause, with adhesions forming after peritoneal injury from surgical intervention 1
• Radiotherapy can trigger peritoneal injury leading to adhesion formation 1
• Endometriosis causes peritoneal inflammation and subsequent adhesion development 1
• Inflammatory conditions within the abdomen result in adhesion formation 1
• Local tumor response can generate adhesions 1
• Congenital adhesions can occur even without prior surgery, particularly in virgin abdomen cases 1

Clinical Presentation

The classic tetrad of symptoms characterizes adhesive small bowel obstruction: 1

• Abdominal pain - typically colicky in nature
• Vomiting - often bilious
• Abdominal distention - progressive
• Constipation - may be absolute in complete obstruction

Important caveat: Elderly patients may not present with all four symptoms, making diagnosis more challenging. 2

Epidemiology and Significance

Adhesions are the single most common cause of small bowel obstruction, accounting for 60-75% of all cases. 1 The condition represents a major surgical problem:

• 80% of small bowel obstructions occur in patients with previous abdominal operations 1, 3
• One in ten patients develops at least one episode of SBO within 3 years after colectomy 1
• Highest risk surgeries include colorectal, oncologic gynecological, and pediatric procedures 1

Recurrence Rates

The condition has significant recurrence risk: 4

• 12% of non-operatively treated patients are readmitted within 1 year (rising to 20% at 5 years)
• 8% of operatively treated patients are readmitted within 1 year (rising to 16% at 5 years)

Diagnostic Confirmation

Definitive confirmation of adhesive etiology is made during operative treatment when adhesions are directly visualized. 1

Non-invasive confirmation methods include: 1

• History of previous episodes of bowel obstruction caused by adhesions
• CT scan exclusion of other causes (hernias, malignancy, bezoars, inflammatory bowel disease, volvulus)
• Water-soluble contrast studies showing delayed transit 4, 2

Virgin Abdomen Considerations

Adhesions can occur even without prior surgery (virgin abdomen), accounting for 26-100% of small bowel obstruction cases in patients without previous operations. 4 In male patients specifically, 56% of solitary band adhesions occur without prior abdominal surgery. 5 This challenges the traditional assumption that adhesive obstruction only occurs post-operatively.

Clinical Importance

This is a surgical emergency requiring prompt recognition because: 1

• Bowel ischemia can develop rapidly with strangulation
• Delayed intervention increases morbidity and mortality
• Perforation risk increases with prolonged obstruction
• The condition accounts for nearly 50% of all emergency laparotomies 1