Meckel's Diverticulum

Meckel's Diverticulum (diverticulum Meckeli), a remnant of the vitelline-intestinal duct. In the embryo, the umbilical cord contains, in addition to the umbilical vessels, two more channels: urachus and ductus omphalo-mesentericus. The latter extends from the navel to the lower part of the ileum and connects with it. Normally, the M. d. obliterates in the eighth week of intrauterine life and disappears by the time of birth (only insignificant traces of it remain). According to Hilgenreiner's data, M. d. occurs in adults in approximately 2% of cases. It is usually located 60-70 cm proximal to the ileocecal angle (resp. from valvula Bauhini). In exceptional cases, it may be located far from the Bauhinian valve (up to 250 cm) and close to it. Of all congenital anomalies of the intestine observed in humans, M. d. occurs most frequently. The following types are distinguished: open, closed, and free. The open M. d. has several varieties. In some cases, it represents an intestinal tube connecting the navel opening with the intestinal lumen, i.e., we have before us a completely preserved vitelline-intestinal duct in the form of an intestinal fistula. In other cases, M. d. represents a blind sac extending from the navel inward and ending in a cord connecting the navel with the wall of the small intestine. This is an incomplete regression of the vitelline-intestinal duct. Finally, cases are observed when M. d. represents a blind sac in the navel area, not connected to the small intestine at all. This blind sac penetrates either through the entire thickness of the anterior abdominal wall or only through part of its layers. Sometimes the open M. d. represents a mushroom-like formation on the navel (enterocystoma Kolaczek's, Sarkomphalus Hüttenbrenner's, Divertikelprolaps des Nabels Pernice).-In the closed diverticulum, i.e., in cases where it has no communication with the outside world, adhesions are observed with it by means of a cord either to the navel or to the anterior abdominal wall or to the mesentery, to the intestine or to the posterior abdominal wall.-The free M. d. is most common. It represents a blind diverticulum of the small intestine on the side opposite to the point of attachment of the mesentery.-The M. d. has the same appearance as the ileum, and the structure of its wall usually does not differ from that of the latter. Sometimes, however, areas of mucous membrane are found in the M. d., constructed according to the type of the gastric fundus mucosa (see below). The length of the M. d. varies-from a few millimeters to 8 or more centimeters (in the case of Rostovtsev-26 cm). The diameter varies from the thickness of a goose quill to the width of the small intestine and more.-M. d. occurs twice as often in men as in women. Its end is usually dome-shaped, less often conical. The feeding vessels run along the wall in the form of a single artery and vein. From a clinical point of view, M. d. can be of threefold interest: 1) the cord connecting it to the navel can cause intestinal obstruction due to compression, kinking, or twisting of the loop of the small intestine; 2) the diverticulum can become inflamed, similar to inflammation of the vermiform appendix (diverticulitis), and 3) the diverticulum can represent an intestinal fistula. Littré initially described the Meckel diverticulum in the hernial sac, but since usually a portion of the intestinal wall also passes into it, the name "Littré's hernia" was transferred to the hernia of the intestinal wall. This not very rare variety of hernia is most often found in a state of incarceration. Most often, M. d. is the cause of intestinal obstruction, which occurs in men more often than in women (4:1). Obstruction is formed due to twisting of the intestinal loop around the cord formed by the diverticulum, or due to kinking. In exceptional cases, at the point where the diverticulum opens into the small intestine, a spur may form between the afferent and efferent segments of the small intestine, which causes obstruction. When the M. d. is free, detached from the intestine and anterior abdominal wall and represents a kind of cyst, it can acquire the character of a tumor resembling an enteroteratoma. This tumor is called an enterocystoma.-Most often, M. d. gives complications at a young age (up to 30 years-67.7%). Multiple diverticula, sometimes found on the thin intestines, have nothing to do with the true M. d. Sometimes pocket-like protrusions of the M. d., its tumors, additional pancreatic glands in its wall may be observed. Ulcers of the M. d. are described (usually in childhood). Their interest lies in the fact that they usually occur in the presence of areas of mucous membrane in the M. d., constructed according to the type of the gastric fundus glands. At the same time, it is indicated that the ulcer itself develops not on the gastric, but on the intestinal part of the diverticulum's mucous membrane, and precisely where the boundary between these parts passes. Such findings are put forward as proof in favor of the cauterizing action of gastric juice (Büchner) in the formation of classic gastric ulcers. Clinically, ulcers of the M. d. can simulate appendicitis. The contents of the diverticulum can be fecal matter, intestinal parasites, foreign bodies (when communicating with the intestine), mucus, acetone, cholesterol, serum-albumin (when the lumen is obliterated), pus (in inflammation), colloidal fluid, hemorrhagic exudate (in twisting), etc. The diagnosis of open M. d. usually does not present great difficulties (congenital fistula in the navel area). In most cases, with a closed or free diverticulum, the diagnosis is made during the operation undertaken for intestinal obstruction, appendicitis, etc. When a cord causing obstruction is present, it is incised between ligatures. When a free diverticulum in the form of a blind diverticulum of the small intestine is present, it is removed in the same way as the vermiform appendix during appendectomy, or by resection with the corresponding segment of the small intestine, depending on the diameter of the diverticulum's base. The open M. d. is closed surgically, like an intestinal fistula.