Ogilvie syndrome is that the acute dilatation of the colon within the absence of any mechanical obstruction in severely ill patients. Acute colonic pseudo-obstruction is characterized by massive dilatation of the cecum (diameter > 10 cm) and right colon on abdominal X-ray. it's a kind of megacolon, sometimes mentioned as "acute megacolon," to differentiate it from toxic megacolon. the precise mechanism isn't known. The probable explanation is imbalance within the regulation of colonic motor activity by the autonomic systema nervosum . it's been postulated that reactivation of varicella zoster virus (which causes chickenpox and shingles) within the enteric ganglia could also be a explanation for Ogilvie syndrome