<prompt> Investigation of choice in hirschsprugs disease is ?Rectal manometryRectal examinationRectal biopsyBa enema  <response>: Answer c i.e. Rectal biopsy Definitive diagnosis is made by rectal biopsy. The histopathology of Hirschprungs disease is the absence of ganglion cells in the nerve plexus, presence of hyperophied nerve bundles and increased acetylcholinesterase-positive nerve fibres. 