What is the reason for the narrow anus?

Anal stricture is caused by many reasons.

First, congenital anal stricture, born with a small anus, is congenital anorectal dysplasia.

Second, acquired anorectal stricture, the main cause is trauma or burns, sometimes causing scars, resulting in anal stricture.

Third, anal surgery, such as internal hemorrhoids or mixed hemorrhoids surgery, if the mucosa and skin damage too much during surgery, sclerotherapy injection too deep, this may lead to inflammation around the anal rectum, thus forming scars, resulting in stricture.

Fourth, rectal malignant tumor, rapid growth of tumors leading to compression infiltration, so that intestinal stenosis. So there are many reasons for anal stricture.