Meckel’s diverticulum

An omphalocele is the presence of midgut structures in the umbilical cord remnant. A variety of intestinal content may be present within the defect. The midgut is malrotated. Some patients have other anomalies. An omphalomesenteric cyst is formed when both omphalomesenteric duct ends involute, leaving a persistent central cavity.Most are incidental findings, with an occasional one becoming infected or compressing and obstructing an adjacent structure. A persistent fibrous omphalomesenteric remnant between the umbilicus and midgut is a potential source for small bowel volvulus around the fibrous band.

this is radiology images of Diagram of a Meckel’s diverticulum arising from the antimesenteric small bowel border (arrows) and connected to
the abdominal wall by a fibrous tract. B: Instead of a fibrous tract, an omphalomesenteric duct connects bowel to skin.

A Meckel’s diverticulum is the most common congenital gastrointestinal tract abnormality. It results from persistence of the embryonic yolk sac. Most Meckel’s diverticula are asymptomatic but they can be involved in two clinical scenarios: More common is the patient presenting with bleeding suspected from gastric mucosa in a Meckel’s diverticulum, with bleeding usually being gradual rather than massive. Less often encountered is the patient with sequelae to inflammation or intussusception. Obstruction is more common in patients under the age of 10 years, and perforation is more common in young adults. A rare Meckel’s diverticulum first manifests in the elderly.

Meckel’s diverticula vary in size and shape, with an occasional one being very large. A rare one even has a second outpouching, or daughter diverticulum, connected to the main diverticulum. Ultrasonography reveals an uncomplicated, fluid-filled Meckel’s diverticulum as a cyst-like structure. Some of these diverticula mimic an appendiceal mucocele, mesenteric cyst, enteric duplication,or even a cystic ovarian tumor if a separate ovary cannot be identified by imaging.

This is radiology images of Meckel’s diverticulum (arrow), detected on a retrograde small bowel examination.

Complications of Meckel’s diverticulum
Ectopic gastric mucosa is found in 20% to 50% of patients with Meckel’s diverticula and “gastritis” is common in those with gastric mucosa; only an occasional one contains H. pylori. Similar to the stomach, gastric secretions by this ectopic mucosa are stimulated by hormonal factors. As expected, hemorrhage and perforation develop in a setting of ectopic gastric mucosal tissue.

It should be emphasized that a Meckel’s scan detects only the presence of gastric mucosa, rather than hemorrhage or other complications. Gastric mucosa enhances more than any other bowel mucosa on postcontrast MRI, and any gastric mucosa in a Meckel’s diverticulum reveals marked enhancement. A stone (or bezoar) passing into the ileal lumen can cause bowel obstruction and mimic gallstone ileus. A rare enterolith within a Meckel’s diverticulum obstructs the diverticular communication with bowel lumen and leads to diverticulitis. Imaging should identify such a calcified enterolith; superficially an appendicolith is in the differential.

Perforation of a Meckel’s diverticulum is commonly ascribed to ulcerated heterotopic gastric mucosa. An 8-day-old boy perforated a Meckel’s diverticulum, a highly unusual age for this to occur; no ectopic gastric tissue was found in the resected specimen, and a narrow diverticular neck was believed to have led to poor emptying, subsequent inflammation, and perforation. Inflammation does result in Meckel’s diverticulitis. A CT scan showing a fluid-filled cavity surrounded by a thickened, contrast-enhancing wall suggests diverticulitis.

Conventional radiography detects a perforation or suggests an obstruction; CT and US identify the site of obstruction and any abscesses and often suggest the underlying etiology. Tumors similar to those found throughout the gastrointestinal tract also develop in Meckel’s diverticula. A number of these are detected incidentally when a diverticulum is resected for unrelated reasons. These tumors range from adenomas and carcinomas to sarcomas, and originate from either ileal or gastric epithelium. A leiomyosarcoma originating in a Meckel’s diverticulum contained a 4-L cystic component, presumably secondary to necrosis. A rare neuroendocrine tumor has developed in a Meckel’s diverticulum.

Therapy
If an incidental Meckel’s diverticulum is discovered, some surgeons recommend that a diverticulectomy be performed; others argue that the risk of complications, although low, does not justify a prophylactic resection. A morbidity of 2% and zero mortality was found in a retrospective study of 90 patients who had an incidental diverticulectomy; using decision analysis the authors concluded that an incidental diverticulectomy in adults should be abandoned. Bleeding and obstruction are the primary presentations in patients requiring surgery for symptomatic Meckel’s diverticula. Less frequent indications for surgery are an acute abdomen due to perforation, diverticulitis, or intussusception.

Share :