why is Hirschsprung's disease associated with a contracted aganglionic segment rathe

[robertfw]

My understanding of Hirschsprung's disease is an aganglionic region of the sigmoid colon.

I also understand that there is an increase in acetylcholinesterase activity in the parasympathetic nerves in that region.

I understand the parasympathetic nerves are stimulatorary to the region, which I understand to mean causes contraction.

I also know that Hirschsprung's disease causes increased spasticity, i.e. continual contraction of the region.

Finally I understand the acetylcholinesterase inactivates acetylcholine preventing any further transmission.

Therefore, if acetylcholinesterase is high in the parasympathetic nerves causing a reduction in active acetylcholine, reducing nerve transmission from the stimulatorary parasympathetic nerves, how come the sigmoid colon is not constantly relaxed and dilated, as opposed to constantly contracted? Help please. Can anyone enlighten me?