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