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Ogilvie syndrome, or acute colonic pseudo-obstruction, is the acute dilatation of the colon in 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 is a type of megacolon, sometimes referred to as "acute megacolon," to distinguish it from toxic megacolon.
The condition carries the name of the British surgeon Sir William Heneage Ogilvie (1887–1971), who first reported it in 1948. Reproduced in:
Ogilvie syndrome is an acute illness, which means it occurs suddenly and temporarily, and it only affects the Large intestine. "Intestinal pseudo-obstruction" is a broad term that refers to any paralysis of the intestines that is not caused by a mechanical obstruction. Some individuals develop chronic intestinal pseudo-obstruction as a result of a chronic disease or a congenital condition.
Acute megacolon develops because of abnormal intestinal motility. Normal colonic motility requires integration of myogenic, neural, and hormonal influences. The enteric nervous system is independent but is connected to the central nervous system by sympathetic and parasympathetic nerves. The targets of the are , secretory cells, , microvasculature, and inflammatory cells. The neurons in the enteric plexuses are stimulated by a food bolus, which both distends the gut and stimulates the mucosal surface, leading to the release of factors that stimulate . The stimulated interneurons transmit excitatory signals proximally, which cause contraction and inhibitory signals distally, and these in turn cause relaxation. These signals are transmitted by the acetylcholine and serotonin, among others.
Acute megacolon can also lead to ischemic necrosis in massively dilated intestinal segments. This is explained by Pascal's law and Laplaces's law. Pascal's principle states that a change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid; the pressure across all parts of the lumen is equal. Laplace's law states that:
where T is wall tension, P is pressure, r is the radius, and t is wall thickness. Since the wall tension is proportionate to the radius, a dilated intestinal segment has a greater wall tension than a nondilated segment; if the dilatation and tension are sufficiently great, blood flow may be obstructed and ischemia of the bowel will occur. Ogilivie syndrome may precipitate volvulus.
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