Anal stenosis occurs when the muscular valves that normally keep stool inside the rectum (anal sphincter) are smaller than normal. The stool may not be able to pass through the small opening.
A baby may be born with this condition (congenital). But narrowing of the rectum can also occur after surgery to rejoin the intestine to the rectum.
Anal stenosis can be treated.
WebMD Medical Reference from Healthwise