Acute abdomen: intestinal obstruction

Intestinal obstruction is a common and dangerous surgical emergency that is associated with a high mortality if managed inappropriately; results are usually good if it is diagnosed and treated early. Obstruction of the small intestine and large intestine are fundamentally different in their cause and management (although differentiation between the two merges in distal small-intestine and proximal large-intestine obstruction). In general, obstruction of the small intestine presents with colicky abdominal pain and vomiting, whereas distension and absolute constipation tend to be more common in obstruction of the large intestine. The causes of intestinal obstruction can be mechanical or paralytic in origin, and can be subdivided into small- and large-intestinal obstruction. Obstruction of the large intestine accounts for about 80% of all intestinal obstructions (the most common cause in 'developed countries' is adhesions), whereas adenocarcinoma of the colon is the most common cause of obstruction of the large intestine. A number of pathophysiological changes occur in intestinal obstruction, and these changes determine the clinical picture. Obstruction of the small intestine is characterized by dehydration and hypovolaemia due to fluid losses; obstruction of the large intestine is influenced by the competency of the ileocaecal valve. These features are diagnosed clinically and by radiography, but the decision to operate is a clinical (based on abdominal examination and clinical suspicion of potential pathology). Despite improvements in management, the mortality ranges from 10-30% (depending on type of obstruction and the presence of perforation) in the UK.