Lower abdominal and pelvic surgeries lead to obstruction more often than upper gastrointestinal surgeries. Strangulated obstructions are surgical emergencies. If not diagnosed and properly managed, vascular compromise leads to bowel ischemia and further morbidity and mortality. This leads to increased peristalsis both above and below the obstruction. Frequent loose stools and flatus are seen 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, there is increased hydrostatic pressure in the capillary beds. This results in massive third spacing of fluid, electrolytes, and proteins into the intestinal lumen. Fluid loss and dehydration that ensues may be severe and contribute to the morbidity and mortality of these patients.