How does a midgut volvulus occur, and why is this a surgical emergency?
Lack of attachment of the midgut to the posterior abdominal wall allows the midgut to twist on a shortened root mesentery, which results from lack of complete rotation.
This twisting is called a volvulus, and it causes small bowel obstruction with concomitant obstruction of the lymphatic and venous supply of the bowel and eventually the arterial supply.
Subsequently, bowel ischemia and necrosis ensue. If it is not repaired within several hours, all of the bowel supplied by the superior mesenteric artery (second portion of the duodenum to midtransverse colon) undergoes infarction.