Bowel obstruction is classified as mechanical (physical blockage) or functional (paralytic ileus from impaired peristalsis). Small bowel obstruction (SBO) accounts for 80% of cases, most commonly from postoperative adhesions. Large bowel obstruction (LBO) is most commonly caused by colorectal cancer. As the bowel dilates proximal to the obstruction, massive third-spacing of fluid occurs (up to 8L/day can sequester), causing hypovolemia, electrolyte derangements (hypokalemia, metabolic alkalosis from vomiting), and risk of bowel ischemia. The nurse manages fluid resuscitation, NG decompression, electrolyte correction, and monitors for surgical indications.