Megacolon is an abnormal dilation of the colon (a part of the large intestines). The dilatation is often accompanied by a paralysis of the peristaltic movements of the bowel. In more extreme cases, the feces consolidate into hard masses inside the colon, called fecalomas (literally, fecal tumor), which can require surgery to be removed.
A human colon is considered abnormally enlarged if it has a diameter greater than 12 cm in the cecum (it is normally less than 9 cm), greater than 6.5 cm in the rectosigmoid region and greater than 8 cm for the ascending colon. The transverse colon is usually less than 6 cm in diameter.
A megacolon can be either acute or chronic. It can also be classified according to etiology.
Read more about Megacolon: Signs and Symptoms, Cause, Diagnosis, Treatment