 relapsed for more than four years.

Literature Review
In order to understand inverted Meckel's diverticulum, the PubMed database was searched from its inception to February 2022 using the keyword "inverted Meckel's diverticulum", and the search language was limited to English. In total, 94 related articles were retrieved. There were 29 articles for 74 adult [3,7-25] and 9 pediatric (age < 18 years) [2,[26][27][28][29][30][31][32] cases including the present case] that reported the course of each case in detail. These included 55 male and 28 female patients with onset ages of 2 to 78 years. Clinical symptoms, duration from onset to treatment, positive diagnostic modalities, treatment, and pathological findings were compared between children and adults. Quantitative data were analyzed by Student's t-test and the Mann-Whitney U test. For the categorical data, the χ 2 test was performed when there was a sufficient number of cases, and Fisher's exact test was performed for the analysis involving a relatively small number of columns. The significance level was p < 0.05 in the two-sided test. In the comparison between adult and pediatric cases, pediatric cases with an inverted Meckel's diverticulum were significantly less likely to show melena (p = 0.019) and had clinical features tending to cause intussusception (p = 0.001). In addition, the pediatric cases were operated on within a significantly shorter time from onset than the adult cases (p = 0.019) ( Table 1).

Short Summary
A pediatric case of inverted Meckel's diverticulum diagnosed by abdominal ultrasonography and DBE, in which the patient was diagnosed as having cyclic vomiting due to recurrent abdominal pain and vomiting by a referring physician, was described. Initially, because of high fecal human Hb levels during abdominal pain and vomiting attacks, abdominal ultrasound was performed, and incomplete ileal intussusception was diagnosed with findings of multiple concentric ring signs and the pseudokidney sign, which resolved spontaneously during the disease course. Finally, laparoscopic-assisted resection of a pedunculated polyp-like structure identified at approximately 90 cm proximal to the ileocecal valve, which is a preferred site for Meckel's diverticulum, led to the definitive diagnosis of inverted Meckel's diverticulum with histological findings of ectopic gastric mucosa. After resection of the lesion, no recurrence of gastrointestinal symptoms has been observed.

Meckel's Diverticulum
Meckel's diverticulum is a residual structure of the embryonic yolk duct, and most cases are diagnosed by bloody stool and obstructive bowel symptoms such as abdominal pain and vomiting. Symptomatic Meckel's diverticulum cases are estimated to account for about 30% of all Meckel's diverticulum cases [1,33,34]. About 50% of symptomatic cases requiring a surgical procedure were reportedly diagnosed at less than five years of age, with sex ratios (M:F) between 1.5:1 and 4:1 [33]. In symptomatic or hemorrhagic cases of Meckel's diverticulum, approximately 53% showed ectopic tissue, and approximately 80% of those were gastric mucosal tissue [35]. Therefore, the diagnosis may be difficult in cases with an atypical onset age and the only obvious clinical manifestation is abdominal pain, as in the present case. Indeed, the diagnosis of the present case was complicated by the fact that the fecal occult blood test was positive during the gastrointestinal attack, but no obvious bloody stool was evident, despite the ectopic gastric mucosal tissue that was present within the advanced mass lesion on histological examination. In the literature review including the present case, bloody stool was observed in 55/74 (74.3%) of adults and 3/9 (33.3%) of children, with a significant difference (p = 0.019) ( Table 1). Although it may not be sufficient to conclude that the diagnosis of inverted Meckel's diverticulum is usually delayed in pediatric cases because of the absence of bloody stool, eight pediatric cases, excluding the present case, resulted in ileus due to intussusception, and imaging findings of intussusception were observed significantly more often in children than in adults (p = 0.001) [2,3,. On the other hand, adult cases may have significantly more anemia due to chronic intestinal hemorrhage (p < 0.0001) ( Table 1), because the adult cases do not present with the acute onset of intussusception, unlike the pediatric cases.

Clinical Course
The present patient had periodic abdominal pain and vomiting from the age of eight years, suggesting that the Meckel's diverticulum inverted during the same period, and there was repeated ileo-ileal intussusception. Previous reports suggested that the symptoms of small intestinal intussusception were nonspecific and usually detected incidentally by abdominal CT or ultrasonography, with a high rate of spontaneous resolution. However, symptomatic cases were often difficult to treat noninvasively, leading to surgical intervention [36,37]. The present review also showed that 5/9 (62.5%) of the pediatric patients underwent emergency surgery within several hours to days after the onset of symptoms, and the median time from onset to surgery was significantly (p = 0.019) shorter in children [0.1 (0.02-6) months] than in adults [3.5 (0.03-60) months] (Table 1). Thus, in children, although the existence of a mechanism leading rapidly from inversion to irreversible intussusception was suggested, the elective procedure had been performed prior to the occurrence of irreversible intussusception in the present case.

Diagnosis and Treatment
A reason for the rapid diagnosis of the present case was that the positive fecal occult blood examination led to abdominal screening by ultrasonography. In the review, abdominal CT and ultrasonography were used in 42/74 (56.8%) and 2/9 (22.2%), respectively, of the adult patients and 14/74 (18.9%) and 8/9 (88.9%), respectively, of the pediatric patients. Abdominal ultrasonography was primarily used as a diagnostic modality in children, with a positive finding rate of 8/8 (100%) ( Table 1). Therefore, the results suggest that abdominal ultrasonography is not only radiation-free and noninvasive compared to abdominal CT, but it is also a useful tool in the diagnosis of intussusception caused by advanced pathological lesions, including inverted Meckel's diverticulum in children. On the other hand, a Meckel's scan was performed in six adult patients including cases with ectopic gastric mucosa, but all cases had negative findings, indicating that a Meckel's scan may not be effective in diagnosing inverted Meckel's diverticulum. DBE was performed in six adult patients, and positive findings were observed in 6/6 (100%), but the present study was the first in which DBE was performed in a pediatric case. It was thus demonstrated that an inverted Meckel's diverticulum could be clearly visualized by DBE even in children. However, endoscopic therapeutic resection of an inverted Meckel's diverticulum in pediatric cases may not yet be practical because of the absence of endoscopic procedure case reports in children and the few institutions providing prompt surgical support in emergencies. However, the differential diagnosis of inverted Meckel's diverticulum with a mass-like leading point, as in the present case, includes isolated small intestinal pedunculated polyps. In the case of small intestinal polyps, small intestinal balloon endoscopy is useful in performing polypectomy without invasive surgery [38]. In addition, the presence of small intestinal polyps may suggest the possibility of juvenile polyposis syndrome [38], and small intestinal balloon endoscopy may also contribute to screening for such a disorder.

Conclusions
A case of inverted Meckel's diverticulum that mimicked cyclic vomiting due to recurrent abdominal pain and vomiting was presented. This case was promptly diagnosed by DBE, resulting in prevention of intestinal perforation and obstruction and exclusion of a small intestinal polyp and polyposis. In cases involving periodic attacks of vomiting and abdominal pain, unnecessary emergent surgery could be avoided by cautious imaging evaluation, considering ileo-ileal intussusception with an advanced lesion of an inverted Meckel's diverticulum as a differential diagnosis, without facilely diagnosing cyclic vomiting. In addition, the novelty of this case consists of the fact that the inverted Meckel's diverticulum did not result in an evolving intussusception in a child patient. Thus, the necessity of emergent surgery is not always related to a thorough clinical and imaging evaluation, but to the possibility of an inverted Meckel's diverticulum causing an evolving intussusception, especially in adults. Thus, an inverted Meckel's diverticulum alone is not an indication for emergency surgery, but complications of Meckel's diverticulum such as unresolved intestinal intussusception with intestinal ischemia may prompt an emergent surgical exploration. Institutional Review Board Statement: Ethical review and approval were waived for this study due to its retrospective observational design.
Informed Consent Statement: Written, informed consent was obtained from the patient's parents to publish this manuscript.

Data Availability Statement:
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy.In early 2014 discussions in the media regarding the lack of women conductors prompted academics in the music department at Morley College to respond, by introducing a pilot course for women conductors. This course was designed for women aged 16-19 as an introduction to conducting, to give them the confidence and leadership skills needed to follow this career path.
Due to generous funding from Arts Council England Morley is delighted to announce that the initial pilot will now be continued through a series of weekend workshops, to