SYSTEM: GASTROINTESTINAL TRACT
FREQUENCY: 3-5 per 10 000 live births
PATIENT HISTORY: There are no clinical data available for this case.
The specimen consists of the anus of an infant and a hugely dilated rectum. It can be seen from the rectal end that there is no communication, and externally there is a ridge of skin where the anal orifice should be. The appearance is that of an imperforate anus.
(The tear in the rectum did not occur during life, but in removal of the specimen at autopsy.)
Most infants are diagnosed soon after birth when they do not pass meconium or the absence of an anal opening is noted on examination. If the diagnosis is missed, late presentation is usually abdominal distension and vomiting. The perineum of the infant should be carefully examined for a recto-perineal fistula, and meconium in the urine indicates a fistula between the rectum and urinary tract. A detailed examination and radiological investigations should be done for other abnormalities.
There are a range of anorectal malformations that can result from abnormal development of the urorectal septum and cloacal membrane. The anal membrane is derived from the posterior part of the cloacal membrane. Normally the anal membrane ruptures at the end of the 8th week of gestation.
Other developmental anomalies, especially urogenital and musculoskeletal, are found in up to 70% of infants with anorectal malformation; anorectal malformations are part of several syndromes and genetic disorders. In isolated cases a clear aetiology is seldom identified.