What is the main cause of abdominal distention in a patient with intestinal obstruction?

The distension of the bowel proximal to the obstruction is produced by two factors Gas: Swallowed air is the major source because nitrogen is not well absorbed by mucosa. Gases produced by the bacterial fermentation also causes bowel distension but to lesser extent as compared to swallowed air. Fluid: Enormous quantities of fluid from the extracellular spaces are lost into gut and net GI secretion is also enhanced in obstruction. Ref: CSDT 13/e, Page 629; Maingot's 10/e, Page 1162.