Anatomic nature and surgical significance of anal sinus and anal intramuscular glands.

The nature of anal sinus and anal intramuscular glands is well known, but their origin is still discussed. In the past years a surprising new theory about the invagination of the proctodeum into the hindgut was put forward. Evidence supporting this theory would be the existence of an "anorectal band" and "epithelial debris" in the subanoderm formed during total or partial obliteration of the anal sinuses. To characterize these histological structures, the authors examined 62 autopsy specimens with conventional and special immunohistologic staining methods. In none of the examined specimens could the structures mentioned above be detected. Nearly 90 percent of our specimens contained the well known anal sinuses. In fetuses, neonatal deaths, and children, more than one-half of the anal sinuses were accompanied by anal intramuscular glands penetrating the internal anal sphincter, whereas in adult specimens the anal intramuscular glands were rare. Eight postoperative, idiopathic chronic anal fissures and three postoperative anal fistulas examined with the same staining procedures showed epithelial cells at the base of the fissures or fistulas in two cases (25 percent) and three cases (100 percent), respectively. The results reinforce the theory that anal sinuses and anal intramuscular glands are separate anatomic entities and indicate a new theory of anal development. For idiopathic, chronic anal diseases anal sinuses have little surgical significance. Anal intramuscular glands should be the anatomic correlate of anal fistulas.