MD is unique on the antimesenteric border and located at the end of superior mesenteric artery, when intestinal vascular arcades are replaced by straight arteries, and MD is usually supplied by the vitellointestinal artery originating from the ileal branches of superior mesenteric artery. MD is a true diverticulum localized to within 100 cm from ileocecal valve and composed of normal intestinal wall. Its form is usually vermicular, but sometimes its basis is spread out. Most of MD appear as a 3–5 cm fingerlike structure, but occasionally present less than 2 cm long or as a larger saccular lesion with 5–10 cm diameter. The diverticulum can be laid on a side of the mesentery, and during a bowel examination, it is mandatory to explore the two sides of the mesentery to avoid a missed MD. Another type of MD is the “inverted diverticulum,” where the fingerlike structure is inside the bowel. MD is free in the peritoneal cavity in 73.8 % [11] or fixed by a congenital band to the umbilicus or to the mesentery of terminal ileum; this can lead small bowel obstruction with or without volvulus.

MD has an ileal mucosa, but heterotopic mucosa can be found, and then 80–85 % of the ectopic tissue is gastric mucosa, sometimes associated with pancreatic tissue. Isolated pancreatic tissue or duodenal mucosa can be present in MD. Heterotopic tissue is usually identified in symptomatic diverticula, but it can be present in asymptomatic MD. From a series of 583 patients with symptomatic MD reported in 1978, 93 had heterotopic tissue within the diverticulum, especially gastric mucosa (65/93, 69.8 %) and pancreatic tissue (22/93, 23.5 %) [12]. Another series reported 71 heterotopic tissues from 180 symptomatic MD in adult patients (39.4 %), with 59 gastric mucosa (83.1 %) and 9 pancreatic tissues (12.6 %) [13]. Nevertheless, the histology from 806 resected asymptomatic MD in adult was gastric tissue in 67 (8.3 %), pancreatic tissue in 22 (2.7 %), carcinoid tumor in 17 (2.1 %), diverticulitis in 26 (3.2 %), other pathology findings in 16 (2 %), and no abnormalities in 658 (81.6 %). Then, the presence of gastric and pancreatic tissue in MD is predictive to complications, especially bleeding [8, 9]. No relationship to Helicobacter pylori “gastritis” and bleeding was demonstrated [14].

MD is the most prevalent congenital anomaly of the alimentary tract. The rule of two traditionally describes its characteristics, such as a prevalence rate of 2 % in the general population, a male-to-female ratio of 2:1, an incidence rate of 2 % for symptomatic MD, the presence of symptoms before the age of 2 years, a location at a distance of 2 ft to the ileocecal valve, a diverticular length of 2 in., and two types of common ectopic tissues [15].

From autopsy studies, a MD was found in 386 autopsies of 31,499 performed, resulting in a prevalence of 1.23 %, and the current mortality from MD was 0.001 % [16]. From the Pediatric Hospital Information System (PHIS) database in the United States, there were 2389 children with a diagnosis code of MD over a 9-year period (2004–2012) from 4,338,396 children admitted during the study interval (1/1816). Among them, 945 children had a symptomatic MD (1/4590 hospital admissions) [17]. The incidence decreased with age: 56.4 % were under 6 years of age, 26.8 % between 6 and 12 years of age, and 16.8 % were older than 12 years of age. In this study, 74 % were male with a male-to-female ratio of 3:1 [18]. This prevalence confirms the male-to-female ratio for symptomatic MD in the pediatric population reported previously, between 2 and 3:1 [12, 13, 18]. The ratio is similar for asymptomatic MD [13]. Caucasians are overrepresented (63.4 %), while African-Americans were disproportionately less often affected (16.4 %) in the study population [17].

Male predisposition is observed in peptic ulcer disease which may share a similar pathogenesis with bleeding MD. CDX2 is a homeobox transcription factor, and recent studies demonstrated a close relationship between lack of CDX2 expression and differentiation of ectopic gastric tissues in MD. In addition, methylation of CDX2 with downregulation of gene expression is found to be increased in males. Then, sex and specific gene expression may be involved in embryonic gut differentiation into ectopic gastric mucosa and activity of gastric gland cells. More studies are required to confirm this hypothesis, but it seems interesting in trying to explain the male prevalence [19–21].

The risk of developing a complication from a MD should be about 4 % between 0 and 5 years of age. The most common presentations of symptomatic MD are obstruction, intussusception, bleeding, and diverticulitis (Table 19.1).

Intestinal obstruction is the most common complication and was found in 35.6 % of patients, children and adults, due to inflammation, congenital band between the umbilicus and MD or mesodiverticular band and MD (60.3 %), intussusception (28.3 %), or volvulus (11.4 %) (Table 19.2). They are found out during the operation, and in the case of late diagnosis, a small bowel ischemia can require resection concerning sometimes about 1 meter long, with a risk of a postoperative malabsorption. Usually intussusception on MD leads to a severe obstruction and is difficult to reduce, even during surgical procedure.

Rectal bleeding is the second most common symptom (29.8 %). Bleeding can present as hematochezia and melena or, rarely in child, with occult blood loss. Most often, hemorrhage can be brisk presenting with painless bright red blood in stools with or without hypovolemia. The rate of hemoglobin at admission is often lower than 8 mg/dL and requires transfusion frequently [6]. Such cases are usually associated with a MD containing ectopic gastric or pancreatic mucosa with peptic ulceration. Every hematochezia should call forth MD in children.

Peritoneal symptoms or peritonitis can disclose a MD (23.2 %) and the diagnosis of appendicitis is often done. In case of normal appendix during sonography, CT scan, or surgical procedure, the search of MD is mandatory.

In 7.4 % of cases, the child has an inguinal hernia (Littré hernia), and its painless and non-reducible characters have to catch the eye because adhesions between MD and processus vaginalis are frequent. But the diagnosis is most often done during an operation for hernia.

Umbilical flow may reveal a patent omphalomesenteric duct (2.1 %), especially when a failure of cauterization occurs. Then a MD has to be looked for as when there is umbilical sinus or granuloma.

Uncommonly, presentations are enterolith or foreign body within MD [12, 22]. Tumors of MD are also rare in children as leiomyoma, desmoplastic tumor, or lymphoma [23–25].

The preoperative diagnosis of MD is uncommon, and this is often an intraoperative discovery during treatment of small bowel obstruction, intussusception, or peritonitis. Yamaguchi et al. reported that preoperative diagnosis was done in only 34 of 600 patients (5.6 %) in 1978 [12]. But now MD is more often evocated in the preoperative period with improvement of imaging [26, 27].

Plain radiographs are not usually helpful in making the diagnosis of MD, and they are normal in the majority or show nonspecific signs such as small bowel obstruction or perforation. Uncommonly, enteroliths may be seen on plain film, typically triangular and flat, but they are not specific and can be identified in other pathologies: appendicitis, intestinal tubular duplication, urolithiasis or within ovarian dermoid cyst.

Ultrasound is not the most sensitive radiologic examination but can help when a Meckel’s diverticulitis occurs. Nevertheless, in a series of ten patients with diverticulitis who underwent preoperative ultrasound, six were wrongly diagnosed with appendicitis [28].

Contrast studies can detect a MD, and the classical appearance is a blind-ending tubular or saccular structure arising from the antimesenteric border of the distal ileum. The base of MD is spotted by a “mucosal triangular plateau” when the bowel is distended and by a triradiate fold pattern when the bowel is collapsed. Sometimes, mucosal irregularity may be noted, due to ectopic gastric mucosa or filling defects from clots in a bleeding MD. This barium enema seems a less sensitive investigation than small bowel enema, or enteroclysis, for detection of MD, but needs to intubate the duodenum with discomfort and increases the radiation dose [26, 27]. A study reviewing 415 enteroclysis included 13 patients who had a confirmed histological diagnosis of MD, and 11 were correctly identified on enteroclysis with only one false-positive result [29]. In a Japanese study, about 776 patients included 118 barium enemas, 55 (47 %) had a correct diagnosis of MD, but they seem more useful in adult than in pediatric population [18].

CT scan is very useful in diagnosing and assessing the MD complications, particularly for intra-abdominal abscess, obstruction, perforation, or tumor. From 40 patients with MD reported recently (8 children and 32 adults), 26 were asymptomatic and 14 symptomatic. MD was detected on CT scan in 11 of 26 asymptomatic patients (42.3 %) and in 8 of 14 symptomatic patients (57.1 %) presenting small bowel obstruction, diverticulitis, hernia, or bleeding. The amount of peritoneal flat at the level of MD was related to its detection [30]. CT scan is able to identify bleeding from a MD with active extravasation of intravenously injected contrast medium [31]. Recent studies have suggested that CT scan enterography is a useful method for diagnosis of MD [32].

Mesenteric angiography can be used to investigate gastrointestinal hemorrhage with a MD. In the absence of bleeding, a MD can be recognized by demonstrating a persistent vitellointestinal artery [26]. In a study of 16 patients with bleeding, the feeding vitellointestinal artery was identified in 11 of the patients [33]. Angiodysplasia associated with MD was reported, and this association is important to know because it may cause further gastrointestinal bleeding following MD resection [34].

MRI is not yet used for diagnosis of MD and the experience with it remains limited. MR enteroclysis is an alternative to CT enteroclysis and has been used to successfully identify a MD [35]. The advantages are to reduce the dose of ionizing radiation and to evaluate small bowel function through MR fluoroscopy [36].

Technetium 99m pertechnetate scintigraphy is known to accumulate in the mucin-secreting cells in the gastric mucosa, and it is used to visualize symptomatic MD which often contains heterotopic gastric epithelium. The sensitivity of technetium 99m pertechnetate scintigraphy is 85 % in children, decreasing to 54 % in adults [13, 37]. The sensitivity can be increased by administering pentagastrin, glucagon, or H2 antagonist or by imaging with single-photon emission computed tomography (SPECT) allowing a better localization of MD. The reported incidence of ectopic mucosa in MD varies from 15 to 50 %, according to the number of non-symptomatic incidental cases included in each series. False-positive results are due to the presence of ectopic gastric mucosa elsewhere in the bowel, such as duodenal or jejunal duplication, intussusception, volvulus, inflammatory bowel disease as ulcerative colitis, or Crohn’s disease, and in postoperative patients [38]. False-negative results are frequent due to the absence of ectopic gastric mucosa, but other causes have been identified such as the presence of barium from previous radiological examination which can attenuate gamma radiation, and then scintigraphy should not be performed if there is residual contrast medium within the abdomen [39]. Sometimes, it is also possible to have abundant gastric mucosa in a MD with a negative scintigraphy because technetium 99m pertechnetate is taken up by specific cells within gastric mucosa, especially fundic mucosa, not always present when only antral mucosa is within the MD [40]. Then, repeat technetium 99m pertechnetate scintigraphy can improve the results with appropriate preparation [41]. Despite these results, technetium 99m pertechnetate scintigraphy remains helpful in evaluating patients with a suspected MD, especially in children with evidence of gastrointestinal bleeding. Recently, the sensitivity and specificity for ectopic gastric mucosa were reported as 94 and 97 %, respectively [42]. Scintigraphy with tagged red blood cells to detect active hemorrhage may be also useful in detecting and localizing a bleeding MD, but it is not specific [26, 27].