Histopathologic observations of anorectal abnormalities in anal atresia

Over the years from 1992 to 1997, 41 anorectal malformations (ARM) with his topathologic alterations were investigated to determine which morphologic a bnormalities of the distal rectum accompany ARMs. Three other cases showed normal neuromuscular morphology; 9 further cases could not be evaluated owi ng to scanty biopsies. All resected specimens were caudocranially coiled an d cryostat cut at -20 degrees C into serial sections, which were stained wi th a lactic dehydrogenase, succinic dehydrogenase, nitroxide synthase, and acetylcholinesterase reaction as well as hemalum and sirius red. Ten low, 1 5 intermediate, and 10 high forms of anal atresia (AA) were studied. In add ition, six cloacal abnormalities were investigated. In 7 cases (17%) (5 int ermediate, 2 low AAs), the characteristics of Hirschsprung's disease were o bserved. Oligoneuronal hypoganglionosis of the myenteric plexus proximal to the anal floor was diagnosed in 7 AAs (12%). In 10 children with high-type AA and resection of 1-5 cm distal rectum and in all cloacal anomalies (n = 6) defects of the muscularis propria were seen in the rectal-atresia sac. These defects were characterized by hypoplasia of the circular-muscle layer and/or the internal anal sphincter (IAS). Intestinal neuronal dysplasia of the submucous plexus was most frequently observed (12%) in high-type AA. A correlation between innervation anomalies or anomalies of the muscularis p ropria and the type of fistula could not be seen. In conclusion, all cases with high-type AA and cloacal anomalies were characterized by anomalies of the muscularis propria and/or IAS but this was not the case in intermediate and low-type AAs. Anomalies of the enteric nervous system were diagnosed i n 60% of AAs.