Bowel Obstruction

The clinical problem is a blocked bowel that cannot move contents normally. A mechanical obstruction creates a proximal reservoir of swallowed air, intestinal secretions, and fluid; distension and third spacing reduce the circulating volume available to the kidneys and other organs. As pressure rises inside the bowel, wall edema worsens and mucosal blood flow may fall. Ischemia can then progress to necrosis, perforation, peritonitis, shock, and sepsis. Partial obstruction may still allow some stool or flatus, so one bowel movement does not make the condition safe to dismiss. The experienced bedside pattern is distension plus vomiting or nausea, reduced passage, and evolving volume-depletion signs. Constant severe pain, peritoneal findings, hypotension, tachycardia, oliguria, altered mental status, or a rising lactate indicate that the problem may have moved from obstruction to threatened bowel.