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Many clinical trials have been conducted for inflammatory bowel disease (IBD), so various clinical indices (CIs) and endoscopic indices (EIs) have also been evaluated. However, recently, with the progress of IBD management, review of established indices from previous studies, and establishment of new indices, the landscape of the use of indices in clinical trials have changed. We investigated the number and frequency of the indices adapted in recent clinical trials for ulcerative colitis (CI and EI) and Crohn’s disease (CI, EI, index related to magnetic resonance imaging, index for evaluating patient-reported outcomes, and health-related quality of life). Based on the results, we selected representative indices and further reviewed their content and characteristics. Moreover, various definitions, including clinical and endoscopic response or remission, have been described by means of representative indices in clinical trials.

Noninvasive biomarkers of intestinal inflammation can reduce the number of endoscopies in children with inflammatory bowel disease (IBD). This study aimed to prospectively investigate the usefulness of fecal calprotectin (FCP) and fecal immunochemical test (FIT) in pediatric IBD.Patients aged 6-17 years who underwent ileocolonoscopy for established or suspected IBD were eligible for this study. Fecal samples for FCP and FIT were collected before colonoscopy.A total of 251 samples were analyzed: 88 from ulcerative colitis (UC), 74 from Crohn's disease (CD), 75 from healthy controls (HC), and 14 from children with functional gastrointestinal disorders and normal colonoscopy (NC). At IBD diagnosis, both FCP and FIT were significantly higher in the newly diagnosed UC/CD group than in the HC/NC group (P 0.001). The optimal cutoffs of FCP and FIT to predict IBD diagnosis were 217 mg/kg and 87 ng/mL, respectively. Patients without mucosal healing (MH) showed higher FCP and FIT than those with MH in both UC and CD (P 0.001). The FCP increased exponentially as the endoscopic activity score increased. The optimal cutoff values of FCP and FIT for predicting MH were 161 mg/kg and 106 ng/mL for UC and 367 mg/kg and 57 ng/mL for CD, respectively. FCP showed better specificity than the FIT. Patients with CD and normal ileocolonoscopy had elevated FCP during active small intestinal inflammation.Both FCP and FIT correlate well with endoscopic activity in pediatric patients with IBD. The FCP is a superior marker for predicting MH.

The Epstein-Barr virus (EBV) infection status in patients with inflammatory bowel disease (IBD), particularly those using thiopurines, may be associated with the risk of lymphoproliferative disorder and hemophagocytic lymphohistiocytosis. This was the first multicenter survey of EBV infection in Japanese patients with IBD. Factors related to the EBV infection status were also investigated.Five tertiary institutions in Japan participated in this study to examine pediatric and adult patients with IBD. Serum EBV anti-viral capsid antigen (VCA) IgG, EBV anti-VCA IgM, and anti-EBV nuclear antigen-antibody were measured in 495 patients with IBD. The patients' information was obtained from their medical records. Prior EBV infection was defined as anti-VCA IgM negativity and anti-VCA IgG positivity (UMIN000033004).The patients' median age was 25 years (range 0-92 years). Of the 495 patients, nine were anti-VCA IgM-positive and 354 were anti-VCA IgG-positive (seroprevalence: 72.8%). The proportion of patients with prior EBV infection was 0% for those aged 5 years, 60% for those aged 30 years, and 90% for those aged 30 years. The proportion of EBV-uninfected patients using thiopurines was 28.4% (52/183) for all patients and 51.8% (44/85) for pediatric patients. Age was significantly associated with anti-VCA IgG seropositivity (p 0.01, odds ratio: 0.902, 95% confidence interval: 0.880-0.925). No cases of lymphoproliferative disorder, hemophagocytic lymphohistiocytosis, or chronic active EBV infection were reported.Approximately 30% of Japanese patients with IBD were EBV-uninfected, including those using thiopurines. Age was a significant factor for anti-VCA IgG seropositivity.

BACKGROUND AND AIM We retrospectively determined the safety and efficacy of the endoscopic delivery (ED) of capsule endoscopes. METHODS We enrolled 10,156 patients who underwent small bowel capsule endoscopy (SBCE), 3182 who underwent patency capsule (PC), and 1367 who underwent colon capsule endoscopy (CCE), at 11 gastroenterological and nine pediatric centers. RESULTS Small bowel capsule endoscopies, PCs, and CCEs were endoscopically delivered to 546 (5.4%), 214 (6.7%), and 14 (1.0%) patients, respectively. Only mild complications occurred for 21.6% (167/774), including uneventful mucosal damage, bleeding, and abdominal pain. Successful ED of SBCE to the duodenum or jejunum occurred in 91.8% and 90.7% of patients aged

Genetic variants affecting the function of dual oxidase 2 (DUOX2), the catalytic subunit of membrane-bound enzymes that produce hydrogen peroxide, are associated with very early-onset inflammatory bowel disease (VEO-IBD). We report the case of a 1-year-old boy diagnosed with VEO-IBD after presenting with bloody diarrhea. He had pancolitis and an extensive small intestinal ulcerative lesion at age 4 years. Infliximab treatment was successful but was discontinued due to delayed reaction. At age 7 years, treatment with ustekinumab was started, and remission has been maintained for more than 2 years. Whole-exome sequencing identified compound heterozygous missense DUOX2 variants of unknown significance (p.[R1212H];[F1490Y]). Protein expression in the whole-cell lysate and plasma membrane was lower in F1490Y-DUOX2 than in wild-type (WT)-DUOX2. Hydrogen peroxide generation upon ionomycin stimulation was lower in cells expressing R1212H-DUOX2 and F1490Y-DUOX2 than in those expressing WT-DUOX2. The novel, inherited, biallelic DUOX2 mutations may be molecular risk factors of VEO-IBD.

STXBP2, encoding syntaxin-binding protein 2, is involved in intracellular organelle trafficking and is associated with familial hemophagocytic lymphohistiocytosis type 5. Although STXBP2 mutations reportedly cause monogenic inflammatory bowel disease, the clinical course and underlying pathogenic mechanisms remain unclear. We identified a novel mutation in STXBP2 [c.1197delC, p.Ala400fs] in a boy with congenital intractable diarrhea and hemophagocytic lymphohistiocytosis (HLH). HLH was treated with intravenous prednisolone, cyclosporine, and dexamethasone palmitate. Hematopoietic stem cell transplantation (HSCT) along with prophylaxis for graft-versus-host-disease was performed at 5 months of age. Additionally, colonoscopies done before and after HSCT showed mild colitis with cryptitis. The patient showed elevated fecal calprotectin levels and persistent diarrhea even after HSCT and required partial parenteral nutrition. While anti-inflammatory treatment reduced diarrhea, it was not completely normalized even after HSCT, suggesting that the pathogenesis of inflammatory bowel disease associated with STXBP2 mutations involves both hyperinflammation and functional epithelial barrier defects.

Background Fecal microbiota transplantation (FMT) in patients with ulcerative colitis has shown variable efficacy depending on the protocol used. A previous randomized controlled trial reported that anaerobic preparation of donor stool contributes to improved efficacy. Despite the suggestion that viable obligate anaerobes would be decreased through aerobic handling, there have been only a limited number of reports on how these aerobic or anaerobic procedures affect the composition of viable microbiota in the fecal slurries used for FMT. Methods We adopted 16S and 23S rRNA-targeted reverse transcription-quantitative polymerase chain reaction to quantify viable bacteria in fecal slurries. This study utilized specific primers designed to detect obligate anaerobes (including Clostridium coccoides group, C. leptum subgroup, Bacteroides fragilis group, Bifidobacterium, Atopobium cluster, and Prevotella) and facultative anaerobes (including total lactobacilli, Enterobacteriaceae, Enterococcus, Streptococcus, and Staphylococcus). We then calculated the ratio change (RC) between before and after mixing, and compared the resulting values between anaerobic-prep and aerobic-prep in samples fixed immediately after blending (RCAn0 vs. RCAe0) and in samples maintained (under anaerobic or aerobic conditions) for 1 h after blending (RCAn1 vs. RCAe1). Results For most obligate anaerobes, the median RC tended to be less than 1, indicating that the number of obligate anaerobes was decreased by the blending procedure. However, in samples maintained for 1 h after blending, anaerobic-prep counteracted the decrease otherwise seen for the C. coccoides group and B. fragilis groups (P C. leptum subgroup also tended to show higher RC by anaerobic-prep than by aerobic-prep, although this effect was not statistically significant. Among facultative anaerobes, Enterobacteriaceae, Enterococcus, and Staphylococcus showed median RC values of more than 1, indicating that these organisms survived and even grew after mixing. Moreover, oxygen exposure had no significant influence on the survival of the facultative anaerobes. Conclusions The conditions under which the blending procedure was performed affected the proportion of live anaerobes in fecal slurries. The obligate anaerobes tended to be decreased by blending processes, but anaerobic-prep significantly mitigated this effect. Anaerobic-prep may improve the efficacy of FMT by permitting the efficient transfer of obligate anaerobes to patients with ulcerative colitis.

Objectives This multicenter, cross-sectional study aimed to elucidate the efficacy and safety of the AdvanCE capsule endoscope delivery device for children in Japan. Methods The present study analyzed 183 cases of small bowel capsule endoscope (SBCE) insertion performed using the AdvanCE in 154 patients aged less than 18 years at participating institutions between 2013 and 2017. Statistical analyses were conducted to identify factors contributing to the completion rate for the entire small intestine examination, small intestine transit time, adverse events and technical issues. Results The commonest reason for using the AdvanCE was the patient's inability to swallow the SBCE, which was attributed to young age. SBCE was successfully delivered into the stomach or duodenum in 180 cases and was placed in the duodenum in 90% patients. In 89% patients, the entire small intestine was completely examined, and in 63% patients, findings leading to a new diagnosis or involving changing or maintaining the treatment strategy were obtained. No severe adverse events were observed; however, mild adverse events were observed in 35% patients. No factors considerably contributed to the completion rate for the entire small intestine examination or small intestine transit time and onset of technical issues. The factors that contributed to mild adverse events included intravenous anesthesia, technical issue, and absence of prior insertion of a patency capsule using the AdvanCE. Conclusion The AdvanCE is well tolerated and effective for children.

Background and aim Very early-onset inflammatory bowel disease (VEO-IBD), defined as IBD diagnosed before 6 years of age, tends to be refractory to conventional treatment for IBD. However, there have been a few reports about the usage of infliximab for VEO-IBD. This study aimed to evaluate the efficacy and safety of infliximab for VEO-IBD. Methods Medical records of a cohort of children with VEO-IBD who had received infliximab in a Japanese tertiary children's hospital were retrospectively reviewed for their disease characteristics and clinical course. Subjects were categorized into three groups for the descriptive comparison: ulcerative colitis type (UCT), non-UCT with perianal disease (NUC-PD), and non-UCT without perianal disease (NUC-NPD). Results Seventeen VEO-IBD patients (five UCT, five NUC-PD, and seven NUC-NPD) had received infliximab as their first biologic. In the UCT group, infliximab was continued over 54 weeks in two patients, and three eventually required surgery. In contrast, all patients in the NUC-PD and NUC-NPD groups followed up over 54 weeks remained on infliximab, and two of three patients and three of five patients were in remission at week 54, respectively. Infusion reactions occurred in all five UCT, three of five NUC-PD, and two of seven NUC-NPD patients; however, except for two patients with severe reactions, infliximab was continued with premedication and slow infusions. Conclusions Infliximab appeared useful for children with VEO-IBD. Children with NUC-PD and NUC-NPD responded better with less infusion reaction compared with that with UCT.

Although indigo naturalis (IN) is effective for patients with active ulcerative colitis (UC), IN was associated with adverse events (AEs), including pulmonary arterial hypertension (PAH). Our aim was to evaluate the occurrence of IN-associated AEs and to evaluate any IN dose–effect on AEs. A nationwide survey, using questionnaires, was conducted by conducted by the research group funded by the Ministry of Health, Labour and Welfare of Japan, between June 2017 and September 2018. A first questionnaire determined the occurrence of AEs associated with the therapeutic use of IN or herbal medicines containing IN in patients with UC. A second survey identified the clinical characteristics of patients who developed IN-associated critical AEs, namely, liver dysfunction, PAH, and intussusception. Across 337 participating institutions, 49,320 patients with UC were identified, with IN used in 877 (1.8%). AEs were reported in 91 patients (107 events), including liver dysfunction (n = 40), gastrointestinal symptoms (n = 21), headache (n = 13), and PAH (n = 11). No dose–effect relationship between IN and AEs was identified. Liver dysfunction tended to be mild and reversible. Ten cases of intussusception were reported, with 40% of these patients requiring surgical resection. IN-induced PAH was recovered in patients who discontinued to use IN. No IN-associated deaths were reported. IN-associated AEs were identified among patients with UC, with liver dysfunction often being reversible, while surgical resection was required in a high proportion of patients who developed intussusception. Both healthcare workers and patients should adequately recognize the potential for AEs with the use of IN.

The two-stage-type electrostatic precipitator has been used only in limited applications because of its need to accommodate a large flow rate with its compact size. A two-stage-type electrostatic precipitator comprises a precharger and a collecting unit. The grounded electrode in the precharger is generally designed to be quite short. Previous studies on the influence of the grounded electrode length in the precharger on collection efficiency have reported that the amount of particle charge through the precharger decreases for grounded electrodes that are 20- or 80-mm long. The electric field and space charge distributions were calculated for various grounded electrode lengths using the finite-element method, where the ion density distribution was used as the space charge distribution. For a 20-mm-long grounded electrode, the electric field intensity around the high-voltage wire electrode decreased. Additionally, the electric field intensity distribution at close proximity to the grounded electrode has two additional peaks due to the edges of the electrode. With the 80-mm-long grounded electrode, the peaks of the electric field intensity distribution were outside of the high-ion-density region. These results show that the optimal grounded electrode length for particle charging is about three times the distance between the grounded electrode and the high-voltage wire electrode.

BACKGROUND Some monogenic inflammatory bowel diseases (IBDs) are known to be refractory to conventional treatments. Although allogeneic hematopoietic stem-cell transplantation (allo-HSCT) has become a curative therapeutic option for certain monogenic IBDs, its effectiveness regarding endoscopic improvements has not been clarified. METHODS The clinical course and endoscopic findings of patients with monogenic IBDs who were treated with allo-HSCT between December 2017 and November 2018 at the National Center for Child Health and Development, were retrospectively reviewed. The clinical disease activity was assessed using the weighted Pediatric Crohn's Disease Activity Index (wPCDAI) and the endoscopic finding was evaluated using the Simple Endoscopic Score for Crohn's Disease (SES-CD). Clinical remission was defined as a wPCDAI

STING-associated vasculopathy with onset in infancy (SAVI) is a type-I interferonopathy, characterized by systemic inflammation, peripheral vascular inflammation, and pulmonary manifestations. There are three reports of SAVI patients developing liver disease, but no report of a SAVI patient requiring liver transplantation. Therefore, the relevance of liver inflammation is unclear in SAVI. We report a SAVI patient who developed severe liver disorder following liver transplantation. SAVI was diagnosed in a 4-year-old girl based on genetic analysis by whole-exome sequencing. We demonstrated clinical features, laboratory findings, and pathological examination of her original and transplanted livers. At 2 months of age, she developed bronchitis showing resistance to bronchodilators and antibiotics. At 10 months of age, she developed liver dysfunction with atypical cholangitis, which required liver transplantation at 1 year of age. At 2 years of age, multiple biliary cysts developed in the transplanted liver. At 3.9 years of age, SAVI was diagnosed by whole-exome sequencing. Inflammatory cells from the liver invaded the stomach wall directly, leading to fatal gastrointestinal bleeding unexpectedly at 4.6 years of age. In pathological findings, there were no typical findings of liver abscess, vasculitis, or graft rejection, but biliary cysts and infiltration of inflammatory cells, including plasmacytes around the bile duct area, in the transplanted liver were noted, which were findings similar to those of her original liver. Although further studies to clarify the mechanisms of the various liver disorders described in SAVI patients are needed, inflammatory liver manifestations may be amplified in the context of SAVI.

BACKGROUND AND AIM Ustekinumab is a human monoclonal antibody targeting the p40 subunit of both interleukin-12 and interleukin-23 with reported efficacy to treat Crohn's disease. However, few studies have reported the use of ustekinumab for pediatric inflammatory bowel disease. This study aimed to assess the clinical efficacy and safety of ustekinumab in children and adolescents with inflammatory bowel disease. METHODS Medical records of patients aged under 20 years with Crohn's disease or Crohn's disease-like inflammatory bowel disease who had received ustekinumab at a Japanese pediatric inflammatory bowel disease center were retrospectively reviewed for efficacy and safety. The primary outcome was the steroid-free clinical remission rate at weeks 26 and 52. The steroid-free remission rate beyond week 52 was also evaluated. Weighted pediatric Crohn's disease activity index and simple endoscopic score for Crohn's disease were used to assess disease activity. RESULTS Seventeen patients were included (male : female = 8:9, A1a [diagnosed

Background/Aims: There are few published registry studies from Asia on pediatric inflammatory bowel disease (IBD). Registry network data enable comparisons among ethnic groups. This study examined the characteristics of IBD in Japanese children and compared them with those in European children.Methods: This was a cross-sectional multicenter registry study of newly diagnosed Japanese pediatric IBD patients. The Paris classification was used to categorize IBD features, and results were compared with published EUROKIDS data.Results: A total of 265 pediatric IBD patients were initially registered, with 22 later excluded for having incomplete demographic data. For the analysis, 91 Crohn’s disease (CD), 146 ulcerative colitis (UC), and 6 IBD-unclassified cases were eligible. For age at diagnosis, 20.9% of CD, 21.9% of UC, and 83.3% of IBD-unclassified cases were diagnosed before age 10 years. For CD location, 18.7%, 13.2%, 64.8%, 47.3%, and 20.9% were classified as involving L1 (ileocecum), L2 (colon), L3 (ileocolon), L4a (esophagus/stomach/duodenum), and L4b (jejunum/proximal ileum), respectively. For UC extent, 76% were classified as E4 (pancolitis). For CD behavior, B1 (non-stricturing/non-penetrating), B2 (stricturing), B3 (penetrating), and B2B3 were seen in 83.5%, 11.0%, 3.3%, and 2.2%, respectively. A comparison between Japanese and European children showed less L2 involvement (13.2% vs. 27.3%, P< 0.01) but more L4a (47.3% vs. 29.6%, P< 0.01) and L3 (64.8% vs. 52.7%, P< 0.05) involvement in Japanese CD children. Pediatric perianal CD was more prevalent in Japanese children (34.1% vs. 9.7%, P< 0.01).Conclusions: Upper gastrointestinal and perianal CD lesions are more common in Japanese children than in European children.

Six cavities of the same type (TESLA-like shape) made from six different niobium sources or types were produced at KEK using various materials and fabrication methods. Throughout these sequential in-house fabrications, comparisons of the properties of the various materials for use in superconducting radio-frequency cavities were conducted. The advantages and disadvantages of these properties, together with different fabrication methods, were examined. The cavities were fabricated primarily using existing facilities within KEK to control the fabrication quality. Vertical tests to evaluate single-cell cavity performances were conducted at the Superconducting RF Test Facility in KEK. The technical details of each fabrication method and the obtained high-gradient test results are described and discussed.

In this paper we study the (in)approximability of two distance-based relaxed variants of the maximum clique problem (Max Clique), named Max d-Clique and Max d-Club: A d-clique in a graph $$G = (V, E)$$ is a subset $$S\subseteq V$$ of vertices such that for every pair of vertices $$u, v\in S$$ , the distance between u and v is at most d in G. A d-club in a graph $$G = (V, E)$$ is a subset $$S'\subseteq V$$ of vertices that induces a subgraph of G of diameter at most d. Given a graph G with n vertices, the goal of Max d-Clique (Max d-Club, resp.) is to find a d-clique (d-club, resp.) of maximum cardinality in G. Since Max 1-Clique and Max 1-Club are identical to Max Clique, the inapproximabilty for Max Clique shown by Zuckerman in 2007 is transferred to them. Namely, Max 1-Clique and Max 1-Club cannot be efficiently approximated within a factor of $$n^{1-\varepsilon }$$ for any $$\varepsilon > 0$$ unless $$\mathcal{P} = \mathcal{NP}$$ . Also, in 2002, Marin $$\breve{\mathrm{c}}$$ ek and Mohar showed that it is $$\mathcal{NP}$$ -hard to approximate Max d-Club to within a factor of $$n^{1/3-\varepsilon }$$ for any $$\varepsilon >0$$ and any fixed $$d\ge 2$$ . In this paper, we strengthen the hardness result; we prove that, for any $$\varepsilon > 0$$ and any fixed $$d\ge 2$$ , it is $$\mathcal{NP}$$ -hard to approximate Max d-Club to within a factor of $$n^{1/2-\varepsilon }$$ . Then, we design a polynomial-time algorithm which achieves an optimal approximation ratio of $$O(n^{1/2})$$ for any integer $$d\ge 2$$ . By using the similar ideas, we show the $$O(n^{1/2})$$ -approximation algorithm for Max d-Clique for any $$d\ge 2$$ . This is the best possible in polynomial time unless $$\mathcal{P} = \mathcal{NP}$$ , as we can prove the $$\varOmega (n^{1/2-\varepsilon })$$ -inapproximability.

Background Although tacrolimus (TAC) can induce remission in children with refractory inflammatory bowel disease (IBD) or autoimmune gastroenteropathy (AGE), its use in maintenance therapy remains controversial. The aim of this study was to investigate the potential nephrotoxic nature of prolonged TAC use. Methods This retrospective study reviewed children with gastrointestinal disorder who underwent kidney biopsy for the evaluation of renal damage during TAC therapy for >1 year. The clinical and histological features of renal damage were evaluated in this single-institution cohort. Results Eighteen of 121 children with IBD and two children with AGE followed at a national children hospital in Tokyo, Japan, received TAC between August 2006 and April 2013. Among them, five (Crohn's disease, n = 3; autoimmune gastropathy, n = 1; autoimmune enteropathy, n = 1) received TAC for >1 year, and underwent kidney biopsy. All five had achieved remission on TAC, but had histological evidence of chronic nephrotoxicity. Renal damage in one patient with relatively low TAC trough level remained mild. Estimated glomerular filtration rate (eGFR) at the time of kidney biopsy was lower than at the initiation of TAC in all four available patients. Among them, eGFR improved in one patient after the decrease or discontinuation of TAC. Conclusions TAC appeared to be effective in children with refractory gastrointestinal disorder, but long-term use seems to cause irreversible renal damage. Rigorous monitoring of eGFR and kidney biopsy in selected cases should be considered for the proper adjustment of TAC.

Sialidase cleaves sialic acids on the extracellular cell surface as well as inside the cell and is necessary for normal long-term potentiation (LTP) at mossy fiber-CA3 pyramidal cell synapses and for hippocampus-dependent spatial memory. Here, we investigated in detail the role of sialidase in memory processing. Sialidase activity measured with 4-methylumbelliferyl-α-d-N-acetylneuraminic acid (4MU-Neu5Ac) or 5-bromo-4-chloroindol-3-yl-α-d-N-acetylneuraminic acid (X-Neu5Ac) and Fast Red Violet LB was increased by high-K+-induced membrane depolarization. Sialidase activity was also increased by chemical LTP induction with forskolin and activation of BDNF signaling, non-NMDA receptors, or NMDA receptors. The increase in sialidase activity with neural excitation appears to be caused not by secreted sialidase or by an increase in sialidase expression but by a change in the subcellular localization of sialidase. Astrocytes as well as neurons are also involved in the neural activity-dependent increase in sialidase activity. Sialidase activity visualized with a benzothiazolylphenol-based sialic acid derivative (BTP3-Neu5Ac), a highly sensitive histochemical imaging probe for sialidase activity, at the CA3 stratum lucidum of rat acute hippocampal slices was immediately increased in response to LTP-inducible high-frequency stimulation on a time scale of seconds. To obtain direct evidence for sialic acid removal on the extracellular cell surface during neural excitation, the extracellular free sialic acid level in the hippocampus was monitored using in vivo microdialysis. The free sialic acid level was increased by high-K+-induced membrane depolarization. Desialylation also occurred during hippocampus-dependent memory formation in a contextual fear-conditioning paradigm. Our results show that neural activity-dependent desialylation by sialidase may be involved in hippocampal memory processing.

In recent years, an introduction of the photovoltaic (PV) devices has been increasing by promoting the use of renewable energy. The magnitude of the receiving-end voltage is influenced by the PV output power and the impedance of the distribution line. In this paper, we focused leading power factor controls of the power conditioning system for suppression of the receiving end voltage rise. The influences of the controls on PV output power, line loss and power inflowing to substation were qualitatively analyzed by using vector diagrams. The leading power factor required to suppress the voltage rise to the specified value was quantitatively discussed.

Background To evaluate the role of colonoscopy in infants and young children and clarify the distribution of colonoscopy-requiring diseases in this age group. Methods Cohorts of colonoscopies performed at three children’s hospitals in Japan between April 2011 and March 2016 including infants and children younger than six years of age were retrospectively reviewed. Results In total, 453 colonoscopies were performed in 276 infants and young children. Of these 275 (60.8%) were for diagnostic purposes, 177 (39.2%) were performed as follow-up, and one case was performed for treatment. The median patient age at the time of diagnostic colonoscopy was 2.49 years, and there was a male-to-female ratio of 1.72:1. Abnormal macroscopic and/or histopathological findings were noted in 212 (77.1%) cases. Of these, definite diagnoses were established for the presence of eosinophilic gastrointestinal disorders (EGIDs), inflammatory bowel disease (IBD), and polyp/polyposis in 23, 18.5, and 14% of patients, respectively. Among 51 IBD cases, ulcerative colitis, Crohn’s disease, and IBD-unclassified were identified in 47.1, 33.3, and 7.8%, retrospectively via endoscopic examination. Of these, 11 (22%) were eventually diagnosed with monogenic diseases via genetic testing. Of those with rectal bleeding, EGIDs, polyps/polyposis, and IBD were found in 27, 19, and 18%, retrospectively. There were significantly more cases of EGIDs and fewer ones of IBD and polyps/polyposis in patients with rectal bleeding younger than two years of age. Furthermore, 68% of all follow-up colonoscopies were performed in children with IBD. There were no serious complications in our study cohort. Conclusion We determined the role of colonoscopy in infants and young children. Diseases diagnosed using colonoscopy in this age group included IBD, EGIDs, and polyps/polyposis. The increasing trend of patients with IBD and EGIDs worldwide means that the role of colonoscopy in infants and younger children will be more important in the future.