True statement regarding Hirschsprung's disease-
Anorectal manometry is a useful screening procedure for the diagnosis of Hirschsprung's disease. A normal response in course of manometric evaluation precludes the diagnosis of Hirschsprung's disease.
However, the confirmation of diagnosis in case of Hirschsprung's disease is done by rectal biopsy.

Pathogenesis of Hirchsprung disease

The enteric neuronal plexuses develop from neural crest cells, which migrate into the bowel wall during develop­ment, mostly in a cephalad to caudad direction.
Hirschsprung disease results when the migration of neural crest cells arrests at some point before reaching the anus → inappropriate premature death.
This produces an intestinal segment that lacks both Meissner submucosal and Auerbach myenteric plexus.
Loss of enteric neural coordination leads to functional obstruction and intestinal dilation proximal to the affected segment.
Giant ganglia are present
Mucosa is involved and show foldings
Manometry excludes the disease
Rectal biopsy is contraindicated in infants.