What is the pathophysiology of small-bowel obstruction (SBO)?

Updated: Apr 28, 2017
  • Author: Mityanand Ramnarine, MD, FACEP; Chief Editor: Steven C Dronen, MD, FAAEM  more...
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Answer

Small-bowel obstruction (SBO) leads to proximal dilatation of the intestine due to accumulation of gastrointestinal (GI) secretions and swallowed air. Bowel dilatation stimulates cell secretory activity, resulting in more fluid accumulation. This, in turn, leads to increased peristalsis above and below the obstruction, with frequent loose stools and flatus early in its course.

Vomiting occurs if the level of obstruction is proximal. Increasing small-bowel distention leads to increased intraluminal pressures. This can cause compression of mucosal lymphatics, leading to bowel wall lymphedema. With even higher intraluminal hydrostatic pressures, increased hydrostatic pressure in the capillary beds results in massive third spacing of fluid, electrolytes, and proteins into the intestinal lumen. The fluid loss and dehydration that ensue may be severe and contribute to increased morbidity and mortality.


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