Persistence of the anal membrane, so that the anus is closed. The defect is not always complete; sometimes a narrow opening permits the passage of the bowel contents. When completely imperforate, the anus is seen as a dimple (the proctodeal pit) in the skin of the perineum. The latter condition is often associated with atresia of the lower rectum.

If one is called an imperforated anus, one may construe that they are a tight-ass.