Hirschsprung's disease is caused by a developmental failure of the parasympathetic plexuses of Auerbach and Meissner in the gut. Ganglion cells are always absent from the anorectal junction and the extent of the more proximal deficit determines the severity of the condition. In the absence of parasympathetic innervation, the gut is aperistaltic and spastic. Thus, the dilated megacolon is histologically normal, the distension being a result of more distal gut obstruction.
Last reviewed 01/2018