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Anal atresia

Radswiki and Dr Jeremy Jones et al.

An anal atresia (or imperforate anus) refers to a spectrum of anorectal abnormalities ranging from a membranous separation to complete absence of the anus.

Epidemiology

The estimated incidence is at ~ 1 in 5000 births.

Pathology

Clinically there is no anal opening. It can be broadly be classified into high (supralevator) or low (infra levator) sub type depending on location of the atretic portion.

Genetics

Most cases tend to be sporadic with occasional familial forms

Associations

There are frequent associations with other congenital abnormalities.

other atresias
- oesophageal atresia ⁴
VACTERL association
caudal regression syndrome (has associated sacral agenesis and lower limb hypoplasia
may have fistulous tracts with the
- urethra
- vagina
- or have a single cloacal opening

Radiographic features

Plain film / Abdominal radiograph

can be variable depending on the site of atresia (e.g high or low) , level of impaction with meconium and physiological effects such as straining.
may show multiple dilated bowel loops with with absence of rectal gas

Ultrasound

the anus may be seen as an echogenic spot at the level of the perineum and in an atresia this echogenic spot may be absent ⁴.
may show bowel dilatation
an infra coccygeal or transperineal approach may allow differentiation between a high or low sub-type ⁴.