Why is Hirschsprung's disease associated with a contracted aganglionic segment rather than relaxed dilated?

My understanding of Hirschsprung's disease is as follows.

  • It occurs in the aganglionic region of the sigmoid colon.
  • It causes an increase in acetylcholinesterase activity in the parasympathetic nerves in that region.
  • The parasympathetic nerves are stimulatory to the region, which means they causes contraction.
  • Hirschsprung's disease causes increased spasticity, i.e. continual contraction of the region.
  • The acetylcholinesterase inactivates acetylcholine preventing any further transmission.

Firstly, is all that correct?

Presuming it is, if acetylcholinesterase is high in the parasympathetic nerves, which causes a reduction in active acetylcholine, therefore reducing nerve transmission from the stimulatorary parasympathetic nerves, why is the sigmoid colon is not constantly relaxed and dilated, as opposed to constantly contracted?

Can anyone help make this a bit clearer please? Thank you!

Authored By Becky Archer on Wednesday 3rd October 2012