Also termed MEGACOLON, this is a rare congenital disorder characterised by great overgrowth and dilatation of the colon (see INTESTINE). The RECTUM and lower colon have failed to develop a normal nerve network, thus disturbing normal contraction and expansion of these structures. This results in severe, chronic constipation, usually from birth. Treatment is surgical removal of the affected sections, with the remaining colon being joined to the anus.