Localization of the blind rectal pouch in imperforate anus with the CT scanner

Abstract

Localization of the site of atresia in imperforate anus has classically been carried out by the “upside down” radiograph identifying the blind rectal end, pubic bone, and coccyx on lateral X-rays. This method is often inaccurate because of difficulty in identifying the bony structures and absence of air in the blind rectum. We have studied 6 neonates with CT scans of the pelvis: two males with “high” imperforate anus, one male with a “low” imperforate anus, a female with a cloacal anomaly, a normal stillborn, and a baby with myelomeningocele with a normal anorectum. The CT clearly and accurately identifies all bony structures and pelvic muscle aand determines if bowel is present below the pubococcygeal line, or if it ends above it. In addition, the CT software can generate sagittal and coronal (frontal) reconstructed views from the axial sections to identify the blind rectal end and anus and measure the distance between them. Bowel contents (air and meconium) are distinct other pelvic structures, and CT can muscle and other pelvic structures, and CT can identify these. Identification of the blind pouch by CT is not meant to replace the conventional radiographic evaluations, but may be useful in difficult cases. CT has the potential to identify the level of the blind pouch immediately after birth, without waiting for air to reach the blind rectal end.