Bowel Obstruction (Small And Large)

Basics

Obstruction of normal intestinal flow from either mechanical or nonmechanical causes
May be classified into small bowel obstruction (SBO), large bowel obstruction (LBO), and nonmechanical or functional causes
Classified further as either partial, complete, or closed-loop obstruction
Obstruction leads to proximal dilatation of intestines due to swallowed air and accumulated GI secretions, leading to increased intraluminal pressures often causing pain and vomiting
Distended bowel becomes progressively edematous with additional intestinal secretions causing further distention and third spacing of fluid into the intestinal lumen
Decreased mucosal perfusion leads to weakening mural tensile strength placing patient at risk for perforation
Obstruction may lead to intestinal wall ischemia, resulting in increased aerobic and anaerobic bacteria leakage, possibly leading to peritonitis, sepsis, and even death
Closed loop obstruction: Distal and proximal obstruction leading to more rapid increase in intraluminal pressures and arterial/venous congestion, making higher risk for bowel infarction
Mortality is 100% in untreated strangulated obstruction, 8% if treated surgically within 36 hr versus 25% if delayed past 36 hr

SBO:
- 20% of acute surgical admissions
- More common than LBO
- Adhesions: (most common cause) 55–75%
- Hernias: 15–25%
- Malignancies: 5–10%
- Strictures: inflammatory bowel disease
- Trauma: bowel wall hematoma
- Miscellaneous (eg, ascaris infection)
LBO:
- Disease primarily of the elderly
- Carcinoma: 60%
- Volvulus: 15–20%
- Diverticular disease: 10%
- Colitis (eg, ischemic, radiation)
- Crohn disease
- Foreign bodies (eg, bezoars)
Functional, nonmechanical:
- Paralytic ileus (eg, electrolyte abnormalities, injury, medication induced [opioids])
- Pseudo-obstruction (eg, from trauma or postoperative)

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