Ectopic Gastric Mucosa in a Congenital Small Bowel Diverticulum

Abstract

Congenital small bowel diverticula occur in about 2 per cent of adults. Most of these are Meckel's diverticula. The remainder are duplications of the bowel of different embryologic origin. Because of confusion in diagnosis, the relative incidence of the two types is not completely established. Meckel's diverticulum consists of a persisting portion of the yolk sac or vitelline duct. It occurs, therefore, on the antimesenteric side of the bowel at the junction of the cephalic and caudal limbs of the primitive gut loop. This site in the adult is 20 to 100 cm. above the ileocecal valve. The tip of the diverticulum may be joined to the umbilicus by a fibrous cord representing the remainder of the vitelline duct. Bowel duplication is of disputed, and perhaps variable, embryologic origin, but is unrelated to the vitelline duct. Its site is inconstant, but it is most frequent in the ileum and almost always on the mesenteric side. It may be tubular or cystic and may or may not communicate with the normal bowel lumen. In duplication which communicates with the normal bowel, the anatomical similarity to Meckel's diverticulum is such that there is frequent confusion with the latter. This explains the large number of reported cases of “unusual” and “atypical” Meckel's diverticula found far from the usual site in the ileum, and sometimes on the mesenteric side of the bowel (1). Duplication is also known variously as enterocyst, giant diverticulum, inclusion cyst, and ileum duplex (2). Both Meckel's diverticulum and bowel duplication vary widely in size and shape. In both, all four layers of the bowel are present. They are thus distinguished from acquired diverticula, including mucosal herniations and walled-off bowel perforations, which contain no muscular coat. Either Meckel's diverticulum or bowel duplication may contain ectopic gastric or pancreatic tissue. The stimulus for the development of this ectopic tissue is not well understood, but it appears to be active in all types of congenital bowel diverticula (3). Roentgenologic distinction between the two types of congenital diverticula is difficult, and in many cases impossible. Since the symptoms, prognosis, and complications are often similar, and largely unpredictable, it seems desirable for purposes of roentgen reporting to group both under the simple heading of congenital small bowel diverticula. Congenital diverticula of the small bowel are seldom demonstrated roentgenologically, presumably because of their generally small size and their proximity to the bowel. Furthermore, they are often filled with non-opaque intestinal contents which prevent the entrance of barium (4). Nevertheless, their radiographic demonstration is now occurring more frequently. This may be due to increased awareness of these anomalies on the part of radiologists, and also to the increasing frequency of small bowel examinations.