Secondary megacolon in children is usually caused by constipation after anorectal malformation treatment or anorectal malformation surgery. It can also be secondary to constipation caused by perineal trauma, perirectal tumor compression and other reasons. After the primary factors are removed. The difficulty in defecation can be improved, and some of the megacolon can be gradually relieved by conservative treatment. Children with secondary megacolon usually have a clear history of rectal-anal malformation and perineal surgery. Most of them are accompanied by different degrees of anal stenosis and perineal scarring. These features are easily distinguished from congenital and idiopathic megacolon. Recto-anal malformations cause distal rectal dilatation. This dilated segment of bowel with poor peristaltic function is sufficient to cause constipation.