<prompt> True about Ogilvie syndrome are all exceptIt is caused by mechanical obstruction of the colonIt involves entire pa of the large colonIt occurs after previous surgeryIt occurs commonly after narcotic use  <response>: Ogilvie syndrome is the acute dilation of the colon in the absence of any mechanical obstruction in severely ill patients. Colonic pseudo-obstruction is characterized by massive dilatation of the cecum diameter 10 cm and right colon on abdominal X-ray. 