Chronic constipation due to delayed diagnosis of a congenital anal web.

Congenital anal web is a rare form of anorectal malformation. In cases of delayed diagnosis, patients can present with signs ranging from mild constipation to complete bowel obstruction. The diagnosis is made by thorough anorectal inspection and a digital rectal exam. We present the case of a 9-month-old boy with Down's syndrome with chronic constipation secondary to an anal web. To our best knowledge, this is the first report of an anal web in a patient with Down's syndrome presenting with severe chronic constipation.