Losses of liquids and electrolytes, in the plane above the obstruction accumulate large amounts of liquids and gases. Net intestinal secretion is the primary cause of fluid loss and bloating. Loss of the intestine's ability to metabolize fluids evolves from a point adjacent to proximal bowel obstruction. As there is progressive distension, circulation through the intestine decreases and edema of the wall and even necrosis occurs. Edema and accompanying fluid exudate from the wall exacerbate water losses. Finally, vomiting adds to dehydration.

It is a mechanical obstruction with occlusion of the mesenteric blood supply. Blocking the venous outflow allows the accumulation of bloody fluid inside the intestine and its wall. From the gangrenous intestine bacterial toxins leak that pass into the peritoneal cavity and thus septic shock arises, and eventually perforation.