Which test is typically used as an initial screening test for Hirschsprung disease?

Which test is typically used as an initial screening test for Hirschsprung disease?

• A. Colonography
• B. Abdominal radiographs
• C. Anorectal manometry
• D. Rectal biopsy

Answer: (C)

Assessing the rectoanal inhibitory reflex with anorectal manometry is typically used as an initial screening step when Hirschsprung disease is suspected. In normal individuals, rectal distention triggers a reflex that relaxes the internal anal sphincter. In Hirschsprung disease, due to absence of ganglion cells in the distal colon and rectum, this rectoanal inhibitory reflex is absent, so the internal sphincter does not relax appropriately. Because anorectal manometry is noninvasive and can be performed early in evaluation, it helps distinguish Hirschsprung from functional constipation or other causes of neonatal bowel obstruction. If the rectoanal inhibitory reflex is absent, suspicion for Hirschsprung is raised and a rectal biopsy is pursued to confirm the diagnosis by showing absence of ganglion cells in the submucosal and myenteric plexuses. Other tests like contrast enema or plain abdominal radiographs can indicate obstruction or a transition zone but are not as definitive for screening, and biopsy remains the diagnostic standard.

Assessing the rectoanal inhibitory reflex with anorectal manometry is typically used as an initial screening step when Hirschsprung disease is suspected. In normal individuals, rectal distention triggers a reflex that relaxes the internal anal sphincter. In Hirschsprung disease, due to absence of ganglion cells in the distal colon and rectum, this rectoanal inhibitory reflex is absent, so the internal sphincter does not relax appropriately.

Because anorectal manometry is noninvasive and can be performed early in evaluation, it helps distinguish Hirschsprung from functional constipation or other causes of neonatal bowel obstruction. If the rectoanal inhibitory reflex is absent, suspicion for Hirschsprung is raised and a rectal biopsy is pursued to confirm the diagnosis by showing absence of ganglion cells in the submucosal and myenteric plexuses. Other tests like contrast enema or plain abdominal radiographs can indicate obstruction or a transition zone but are not as definitive for screening, and biopsy remains the diagnostic standard.