Prenatal Diagnosis of Anal Atresia - A Case Report.

Anal atresia can be divided into high type and low type depending on the relationship between the distal rectal pouch and the puborectalis muscle. Prenatal diagnosis of anal atresia is very challenging. Indirect findings include dilated distal bowel segments and calcified intraluminal meconium in 2nd & 3rd trimester. Direct findings include no PAMC (perianal muscular complex) and no target sign (hypoechoic anal sphincter and echogenic anal mucosa). PAMC is intact in low atresia, no PAMC can only be applied to high atresia. A visible echogenic anal mucosa excludes all cases of high atresia and most cases of low atresia, with the exception of the mildest cases with only a thin membrane covering the anal opening.