Which exam finding would you expect on rectal examination in Hirschsprung disease?

Which exam finding would you expect on rectal examination in Hirschsprung disease?

• A. Tight anal canal with no stool in vault
• B. Impacted stool with fissure
• C. Large dilated rectum
• D. Soft stool, normal tone

Answer: (A)

In Hirschsprung disease, there is a distal segment of the colon that lacks nerves, leading to a functional obstruction because the internal anal sphincter cannot relax properly. On rectal examination this presents as a tight anal canal with an empty rectal vault—the stool cannot reach or be passed into the distal rectum, so the rectum feels collapsed and devoid of stool. This finding fits the disease mechanism well: obstruction at the distal bowel, with proximal dilation but a non-relaxed distal segment. The other scenarios don’t match this pattern—impacted stool with fissure suggests simple constipation without a distal neural defect; a large dilated rectum would imply dilation of the rectum itself rather than the obstructed distal segment; soft stool with normal tone would not reflect the inhibitory neurotransmitter deficit causing the obstruction.

In Hirschsprung disease, there is a distal segment of the colon that lacks nerves, leading to a functional obstruction because the internal anal sphincter cannot relax properly. On rectal examination this presents as a tight anal canal with an empty rectal vault—the stool cannot reach or be passed into the distal rectum, so the rectum feels collapsed and devoid of stool.

This finding fits the disease mechanism well: obstruction at the distal bowel, with proximal dilation but a non-relaxed distal segment. The other scenarios don’t match this pattern—impacted stool with fissure suggests simple constipation without a distal neural defect; a large dilated rectum would imply dilation of the rectum itself rather than the obstructed distal segment; soft stool with normal tone would not reflect the inhibitory neurotransmitter deficit causing the obstruction.