Imperforate Anus

Published on 21/03/2015 by admin

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Last modified 21/03/2015

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Chapter 42 Imperforate Anus


The congenital malformation known as imperforate anus (anorectal agenesis) involves the anus, the rectum, or the junction between the two. There are two classifications of imperforate anus, related to the placement of the distal end of the colon (the rectum). In high lesions, the rectum ends above the puborectalis sling, the main muscle complex responsible for sphincter control and fecal continence. In low lesions, the rectum has traversed the puborectalis sling, with an abnormal location in the perineum. Affected infants can be expected to have rectal continence after repair.

Along with the imperforate anus, the following may also occur:

The appearance of the defect varies, depending on its severity. A less-involved imperforate anus appears as a deep anal dimple and exhibits strong muscular reaction to pinprick, which indicates innervation of that area. More severe involvement is initially seen as a flat perineum with no dimple and poor muscular response to pinprick, a result of defective perineal innervation and muscle formation. A highly involved defect includes other anomalies as well (Table 42-1). The infant may initially be seen with poorly developed labia, undescended testicles, or ambiguous genitalia. Outcomes are favorable after definitive surgery is performed.

Table 42-1 Associated Anomalies

Type Incidence (%)*
Esophageal atresia 10–13
Intestinal atresia 4
Intestinal malrotation 4
Cardiovascular defects 12–22
Skeletal deformities (spina bifida, agenesis of sacrum) 6
Genitourinary anomalies (renal agenesis, hypospadias, epispadias) 20–54

* Approximate percentages.