Congenital malformations of the intestine are of considerable frequency. The most important are those in which, from a fault of development, a part of the intestine is wanting. These may be part of a general malformation, as in the case of the Siren-malformation (see p. 58). Of the more local malformations the most important are those in which the rectum is occluded. These cases which are included under the name Imperforate Anus (see p. and Fig. ) are of very various degrees of completeness. The rectum may be absent, or it may be obstructed in its course or at the anus, the most hopeful cases from the surgical point of view being those in which only the extreme lower part of the rectum is defective, and the gut is separated from the anus only by a membrane.
There occur also narrowness and defect of the small intestine, especially in the duodenum and lower end of the ileum. The whole intestine is sometimes deficient in length, having something like the form of the letter S instead of the usual convolutions. In such cases the absorption and digestion of food must be defective, but the persons may live on to old age.
The commonest malformation is Meckel's diverticulum. This consists in a finger-like projection from the intestine. It occurs in the ileum, about three or four feet above the ileo-caecal valve in the adult, and about a foot above it in the new-born; it projects from the free convex border of the gut. It is from one to six inches long, possessing the same structure as the intestine, and communicating with the latter; it is narrower in its calibre, being of a diameter rather more than that of the finger. This diverticulum arises by the imperfect closure of the omphalomesenteric duct, and sometimes it is united to the umbilicus by a cord. Very rarely is the diverticulum continued to the umbilicus, and opens there, forming an Umbilical fistula.
Sometimes the diverticulum gets closed more or less completely at its orifice by a fold of mucous membrane or otherwise. In that case the accumulation of intestinal secretion in it may give rise to the formation of a cyst, the Enterocystoma.
Not infrequently the free end of a Meckel's diverticulum becomes adherent to some neighbouring structure. The bridge or band so formed may be the cause of an intestinal obstruction.
The small intestine is sometimes the seat of numerous rounded pouches of various sizes, which are situated on the attached aspect of the intestine, extending partly into the mesentery. They are mostly composed of mucous aud serous coats alone, as if the muscularis had been defective towards the mesenteric attachment, so as to allow of the mucous membrane being pushed outwards.
Leichtenstern, in Ziemssen's Encycl., vii., 1887; Orth, Path. Anat., 1887, i., 764; Bodenhamer, Congenital malformations of the rectum and anus, 1860; Frank, Ueber d. angeborene Verschliessung des Mastdarmes, Wien, 1892; Fitz, (Omphalo-mesenteric remains, cysts, etc.) Amer. Jour, of Med. Sc, July, 1884; Both, (Enterocystoma) Virch. Arch., lxxxvi., 371, 1881; Runkel, Ueber cystische Dottergangsgeschwitlste, Marburg, 1897; Rimbach, Zur Casuistik d. Enterokystome, Giessen, 1897; Edel, (Diverticula) Virch. Arch., cxxxviii., 1894, Catal. Path. Museum, West. Infirmary.