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Background: Very few risk factors for postoperative recurrence (POR) of Crohn's Disease (CD) after ileocecal resection have been identified. The aim of the present study was to verify the association between an a priori defined list of intraoperative macroscopic findings and POR., Methods: This was a prospective observational study including patients undergoing primary ileocecal resection for CD. Four intraoperative factors were independently evaluated by 2 surgeons: length of resected ileum, mesentery thickness, presence of areas of serosal fat infiltration, or abnormal serosal vasodilation on normal bowel proximal to the resected bowel. The primary end point was early endoscopic POR at month 6 and defined as modified Rutgeerts score ≥i2b. Secondary end points were clinical and surgical recurrence., Results: Between September 2020 and November 2022, 83 consecutive patients were included. Early endoscopic recurrence occurred in 45 of 76 patients (59.2%). Clinical and biochemical recurrence occurred in 17.3% (95% confidence interval, [CI], 10.4%-28.0%) and 14.6% of the patients after 12 months. The risk of developing endoscopic and clinical recurrence was 1.127 (95% CI, 0.448;2.834, P = .799) and 0.896 (95% CI, 0.324-2.478, P = .832) when serosal fat infiltration was observed, and 1.388 (95% CI, 0.554-3.476, P = .484), and 1.153 (95% CI, 0.417;3.187, P = .783) when abnormal serosal vasodilation was observed. Similarly, length of the resected bowel and mesentery thickness showed no association with POR. A subgroup analysis on patients who received no postoperative medical prophylaxis did not identify any risk factor for endoscopic POR., Conclusions: The macroscopic appearance of the bowel and associated mesentery during surgery does not seem to be predictive of POR after ileocecal resection for CD., (© The Author(s) 2023. Published by Oxford University Press on behalf of Crohn’s & Colitis Foundation. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Background & Aims: Clinical evidence substantiates a link between inflammatory bowel disease, particularly Crohn's disease (CD), and metabolic dysfunction-associated steatotic liver disease (MASLD). This study aims to explore the underlying molecular mechanisms responsible for this association., Methods: MASLD was induced by administering high-fat and western diets, while inflammatory bowel disease was induced using DSS (dextran sulfate sodium) and the Il10 knockout (KO) mouse model. The investigation into the role of secondary bile acids (SBAs) in ileitis involved employing metagenomic sequencing, conducting metabolomics detection, performing fecal microbiota transplantation, and constructing CD8 + T cell-specific gene knockout mice., Results: In MASLD+DSS and Il10 KO MASLD mice, we observed ileitis characterized by T-cell infiltration and activation in the terminal ileum. This condition resulted in decreased bile acid levels in the portal vein and liver, inhibited hepatic farnesoid X receptor (FXR) activation, and exacerbated MASLD. Metagenomic and metabolomic analysis of ileal contents revealed increased Clostridium proliferation and elevated SBA levels in MASLD-associated ileitis. Experiments using germ-free mice and fecal microbiota transplantation suggested an association between SBA and MASLD-related ileitis. In vitro, SBAs promoted CD8 + T-cell activation via the TGR5, mTOR, and oxidative phosphorylation pathways. In vivo, TGR5 KO in CD8 + T cells effectively alleviated ileitis and reversed the MASLD phenotype. Clinical data further supported these findings, demonstrating a positive correlation between ileitis and MASLD., Conclusion: MASLD-induced changes in intestinal flora result in elevated levels of SBAs in the ileum. In the presence of a compromised intestinal barrier, this leads to severe CD8 + T cell-mediated ileitis through the TGR5/mTOR/oxidative phosphorylation signaling pathway. Ileitis-induced tissue damage impairs enterohepatic circulation, inhibits hepatic FXR activation, and exacerbates the MASLD phenotype., Impact and Implications: Our study provides a comprehensive investigation of the interplay and underlying mechanisms connecting ileitis and metabolic dysfunction-associated steatotic liver disease (MASLD). Secondary bile acids produced by intestinal bacteria act as the critical link between MASLD and ileitis. Secondary bile acids exert their influence by disrupting liver lipid metabolism through the promotion of CD8 + T cell-mediated ileitis. In future endeavors to prevent and treat MASLD, it is essential to thoroughly account for the impact of the intestinal tract, especially the ileum, on liver function via the enterohepatic circulation., (Copyright © 2024 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.)

Background: Pediatric inflammatory bowel disease (IBD) has been known to be a disease predominant in the west. There is scarcity of data on pediatric IBD (P-IBD) from northern India. The objective of our study was to analyze the clinical spectrum of P-IBD in northern India., Methods: A retrospective analysis of 126 children (<18-year old) diagnosed with IBD from January 1999 to December 2019 was done on a pre-designed proforma. It was systematically entered in a MS Excel spreadsheet and analyzed using Statistical Package for the Social Sciences (SPSS) version 21.0. The descriptive phenotypes of Ulcerative colitis (UC) and Crohn's disease (CD) were revised according to the Paris classification., Results: Of 126 children, UC was diagnosed in 76 (60.3%), CD in 44 (34.9%) and IBD-unclassified (IBD-U) in six (4.76%) patients. The mean age at diagnosis was 11.3 years; 38.8% were < 10 years with the male: female ratio of 1.6:1. Sixteen children (12.7%) had very early onset IBD (VEOBD). Overall, the median time to diagnosis in IBD was 12 months (interquartile range [IQR]: 3.25-24), which was as high as 52.5 months (IQR: 11-98) in CD. Pancolitis with bleeding per rectum and ileocolonic involvement with pain in abdomen were the commonest presentations in UC and CD, respectively. Stricturing disease was seen in 27% of CD cases. Relapses were seen in 46% (35/76) of U.C and 23% (10/44) of CD kids. Step-up treatment protocol was employed in them with the use of biologicals in 12% of cases. There was a 2.75-fold rise in the IBD cases in the last 10 years (2010-20). There was reduction in time to diagnosis (21 months vs. 90 months; p - 0.012) and empirical anti-tubercular therapy use (90% vs. 5.8%) in CD over two decades., Conclusion: From our experience in a tertiary care centre in northern India, P-IBD is on the rise. UC is more common than CD. Pancolitis and ileocolonic disease are the commonest disease sites in UC and CD, respectively There is a significant delay in the time to diagnosis in CD. Stricturing disease was seen in a quarter of children with CD., (© 2023. Indian Society of Gastroenterology.)

Crohn's disease (CD) is one of the 2 main phenotypes of inflammatory bowel diseases (IBDs); CD ischaracterized by a discontinuous, spontaneously recurring, transmural immunopathology that largely affects the terminal ileum. Crohn's disease exhibits both a relapsing and progressive course, and its prevalence is on the rise globally, mirroring the trends of industrialization. While the precise pathogenesis of CD remains unknown, various factors including immune cell dysregulation, microbial dysbiosis, genetic susceptibility, and environmental factors have been implicated in disease etiology. Animal models, particularly ileitis mouse models, have provided valuable tools for studying the specific mechanisms underlying CD, allowing longitudinal assessment and sampling in interventional preclinical studies. Furthermore, animal models assess to evaluate the distinct role that bacterial and dietary antigens play in causing inflammation, using germ-free animals, involving the introduction of individual bacteria (monoassociation studies), and experimenting with well-defined dietary components. An ideal animal model for studying IBD, specifically CD, should exhibit an inherent intestinal condition that arises spontaneously and closely mimics the distinct transmural inflammation observed in the human disease, particularly in the terminal ileum. We have recently characterized the impact of disease-relevant, noninfectious microbiota and specific bacteria in a mouse model that replicates CD-like ileitis, capturing the intricate nature of human CD, namely the TNF∆ARE mouse model. Using germ-free mice, we studied the impact of different diets on the expansion of disease-relevant pathobionts and on the severity of inflammation. In this review article, we review some of the currently available ileitis mouse models and discuss in detail the TNF∆ARE model of CD-like Ileitis., (© The Author(s) 2023. Published by Oxford University Press on behalf of Crohn’s & Colitis Foundation. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

There is ongoing debate whether the type of anastomosis following intestinal resection for Crohn's disease (CD) can impact on complications and postoperative recurrence. The aim of the present study is to describe the outcomes of side-to-side (S-S) vs end-to-end (E-E) anastomosis after ileocecal resection for CD. A retrospective comparative study was conducted in consecutive CD patients who underwent primary ileocecal resection between 2005 and 2013. All patients underwent colonoscopy 6 months postoperatively to assess endoscopic recurrence, defined as Rutgeerts' score (RS) ≥ i2. Surgical recurrence implied reoperation due to CD activity at the anastomotic site. Modified surgical recurrence was defined as the need for reoperation or balloon-dilation. Perioperative factors related to recurrence were evaluated. Of the 127 patients included, 51 (40.2%) received an E-E anastomosis. Median follow-up was longer in the E-E group (8.62 vs 13.68 years). Apart from the microscopic resection margins, patient, disease and surgical characteristics were similar between both groups. Anastomotic complications were comparable (S-S 5.3% vs E-E 5.8%, p = 1.00)0. Postoperatively, biologicals were used in 55.3% and 62.7% (p = 0.47) in S-S and E-E patients, respectively. Endoscopic recurrence did not differ between S-S and E-E patients (78.9 vs 72.9%, p = 0.37), with no significant difference in RS values between both groups (p = 0.87). Throughout follow-up, a higher surgical (p = 0.04) and modified surgical recurrence (p = 0.002) rate was observed in the E-E anastomosis group. Type of anastomosis was an independent risk factor for modified surgical recurrence. The type of anastomosis did not influence endoscopic recurrence and immediate postoperative disease complications. However, the wide diameter and the morphologic characteristic of the stapled S-S anastomosis resulted in a significant reduced risk for surgical and endoscopic reintervention on the long term., (© 2023. Italian Society of Surgery (SIC).)

Background: Crohn's disease (CD) represents a significant public health challenge. We identified a combination of beneficial probiotic strains (Saccharomyces boulardii, Lactobacillus rhamnosus, Lactobacillus acidophilus, and Bifidobacterium breve) and amylase that may antagonize elevated bacterial pathogens in the inflamed gut. Our aim was to characterize the effect(s) of this novel probiotic supplement in SAMP1/YitFc (SAMP) mice with CD-like ileitis., Methods: Three groups of 7-week-old SAMP mice were used in this study. The first experimental group was administered 1 dose of the probiotic supplement (probiotic strains + amylase) diluted in sterile phosphate-buffered saline (PBS) (0.25 mg in 100 µL of PBS) every day for 56 days through the gavage technique, the second group had a probiotic supplement (probiotic strains without amylase), and the third group was a control group in which animals were administered sterile PBS. At the end of the treatment, mice were sacrificed and ilea were collected for histological scoring of ileitis and NanoString analysis. Stool samples were evaluated by 16S ribosomal RNA and gas chromatography-mass spectrometry analyses., Results: Histology scores showed that mice treated with probiotics + amylase had a significant decrease of ileitis severity compared with the other 2 groups. 16S ribosomal RNA and gas chromatography-mass spectrometry analysis showed that abundance of species belonging to genus Lachnoclostridium and Mucispirillum schaedleri were significantly increased compared with the other 2 groups, and this increase was associated with augmented production of short-chain fatty acids. NanoString data showed that 21 genes involved in B memory cell development and T cell infiltration were significantly upregulated in probiotic-treated mice and that 3 genes were significantly downregulated., Conclusions: Our data provide experimental proof for a beneficial effect of the designed probiotic formulation on the severity of CD-like ileitis in the SAMP mouse model, involving both alteration of intestinal genetic pathways and microbial rearrangements. Thus, we propose that this novel probiotic mixture should be further tested as an adjuvant therapy in the treatment of biofilm-associated disorders such as CD, in which it has been proven that polymicrobial imbalance plays a critical role in dysbiosis and gut inflammation., (© The Author(s) 2023. Published by Oxford University Press on behalf of Crohn’s & Colitis Foundation. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Endoplasmic reticulum (ER) stress is associated with Crohn's disease (CD), but its impact on host-microbe interaction in disease pathogenesis is not well defined. Functional deficiency in the protein disulfide isomerase anterior gradient 2 (AGR2) has been linked with CD and leads to epithelial cell ER stress and ileocolitis in mice and humans. Here, we show that ileal expression of AGR2 correlates with mucosal Enterobactericeae abundance in human inflammatory bowel disease (IBD) and that Agr2 deletion leads to ER-stress-dependent expansion of mucosal-associated adherent-invasive Escherichia coli (AIEC), which drives Th17 cell ileocolitis in mice. Mechanistically, our data reveal that AIEC-induced epithelial cell ER stress triggers CD103 + dendritic cell production of interleukin-23 (IL-23) and that IL-23R is required for ileocolitis in Agr2 -/- mice. Overall, these data reveal a specific and reciprocal interaction of the expansion of the CD pathobiont AIEC with ER-stress-associated ileocolitis and highlight a distinct cellular mechanism for IL-23-dependent ileocolitis., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: Yersinia infection affects terminal ileum and lymph nodes and could therefore mimic the symptoms of appendicitis. We aimed to systematically characterise the suspected or confirmed abdominal diseases and/or surgeries associated with Yersinia infection., Materials and Methods: This systematic review and meta-analysis was reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A protocol (CRD42016053252) was uploaded to PROSPERO. The searches were conducted in PubMed and EMBASE on October 2, 2020. Original reports on patients with abdominal surgical diseases were included. The primary outcome was to characterise suspected or confirmed abdominal surgical diseases and/or surgeries associated with Yersinia infection, while the secondary outcomes were the positive rate of Yersinia species for each disease and surgery, and to investigate the rate of Yersinia spp. in different geographic regions. We calculated the weighted mean prevalence of positive tests for Yersinia spp. for the different diseases and surgeries according to the detection method and for subgroups based on geographic region., Results: From the search, 33 studies were included in the systematic review and 18 in the meta-analysis. Across geographic regions, the weighted mean prevalence for Yersinia spp. was 51% (95% CI 34%-69%) in mesenteric lymphadenitis, 65% (95% CI 45%-85%) in terminal ileitis, and 8% (95% CI 2%-15%) in normal appendices., Conclusions: Around half of the patients with mesenteric lymphadenitis and terminal ileitis were serologically positive for infections with Yersinia spp. Yersinia infection may cause unnecessary surgery for suspected appendicitis due to symptoms from mesenteric lymphadenitis or terminal ileitis., (Copyright © 2021. Published by Elsevier Inc.)

Lymphangitis and the formation of tertiary lymphoid organs (TLOs) in the mesentery are features of Crohn's disease. Here, we examined the genesis of these TLOs and their impact on disease progression. Whole-mount and intravital imaging of the ileum and ileum-draining collecting lymphatic vessels (CLVs) draining to mesenteric lymph nodes from TNF ΔARE mice, a model of ileitis, revealed TLO formation at valves of CLVs. TLOs obstructed cellular and molecular outflow from the gut and were sites of lymph leakage and backflow. Tumor necrosis factor (TNF) neutralization begun at early stages of TLO formation restored lymph transport. However, robustly developed, chronic TLOs resisted regression and restoration of flow after TNF neutralization. TNF stimulation of cultured lymphatic endothelial cells reprogrammed responses to oscillatory shear stress, preventing the induction of valve-associated genes. Disrupted transport of immune cells, driven by loss of valve integrity and TLO formation, may contribute to the pathology of Crohn's disease., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Patients with inflammatory bowel disease (IBD) are particularly susceptible to behavioral diagnoses, and the microbiome has been repeatedly implicated in the pathogenesis of IBD. The intestinal microbiome's ability to affect behavior has become increasingly recognized and studied. The so-called 'psychobiome' has been linked to a plethora of neurological and psychological diagnoses, including autism and Parkinson's disease. Despite the ability of many bacterial species within the human intestinal microbiome to synthesize neurotransmitters, it has never been previously reported that a single bacterial species is sufficient to induce depression. Here, we demonstrate that our mouse model of Crohn's disease (CD)-like ileitis, the SAMP1/YitFc (SAMP1), does not exhibit baseline behavioral abnormalities. By comparison, SAMP6 mice develop depressive-like behavior that is associated with a rise in the GABA-producing bacterial genus Parabacteroides. We finally demonstrate that administration of Parabacteroides distasonis into our SAMP1 mice induces depressive-like behavior. Colonization with P. distasonis was not associated with increased intestinal inflammation or alterations in other measures of behavior. The intestinal environment of CD may be particularly conducive to colonization with P. distasonis and subsequent induction of depressive-like behavior. To our knowledge, this is the first report of a bacterial species specifically inducing depressive-like behavior., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Purpose: The optimal surgical approach to extensive Crohn's disease (CD) terminal ileitis is debated. To date, no studies have directly compared the short- and long-term outcomes of modified side-to-side isoperistaltic strictureplasty over the valve (mSSIS) to traditional ileocecal resection., Methods: A retrospective, observational, comparative study was conducted in consecutive CD patients operated for extensive involvement of the terminal ileum (≥ 20 cm). Ninety-day postoperative morbidity was assessed using the comprehensive complication index (CCI). Surgical recurrence was defined as the need for any surgical intervention related to CD during the follow-up period. Endoscopic remission was defined as ≤ i2a, according to the modified Rutgeerts score. Deep remission was defined as the combination of endoscopic remission and absence of clinical symptoms. Perioperative factors related to clinical recurrence were evaluated., Results: Eighty-seven patients were included (47 (54%) ileocecal resection and 40 (46%) mSSIS). Median follow-up was 56 (IQR 34.7-94.4) and 72 (IQR 48.3-87.2) months for resection and mSSIS, respectively (p < 0.001). No mortality occurred. Mean CCI was 9.1 vs 8.5 for ileocecal resection and mSSIS, respectively (p = 0.48). Throughout the follow-up, 8 patients in the resection group (17%) and 5 patients in the mSSIS group (12.5%) experienced surgical recurrence (p = 0.393). Thirty-seven (92.5%) of patients kept the mSSIS. No difference in deep remission was observed (41% vs 22.5%, p = 0.34)., Conclusions: Modified SSIS seems to be non-inferior in terms of safety, recurrence, and durability to traditional resections with the advantage of mitigating the risk of a short bowel syndrome. Larger prospective studies are required to confirm these findings.

Objective: We aim to analyze the diagnostic yield, diagnostic accuracy, and delayed diagnosis of patients with terminal ileum lesions, providing follow-up suggestions for suspected patients., Methods: We carried out an analysis of 1099 patients who had terminal ileum lesions in our hospital from 2009 to 2019. The endoscopy reports and histopathology reports of terminal ileal biopsies were recorded. Clinical diagnosis and management were reviewed to determine whether there was a need to correct after a follow-up endoscopy result., Results: A total of 1099 patients were found to have terminal ileum lesions, among which 959 in 1099 patients (87.26%) were diagnosed as benign, 17 in 1099 patients (1.55%) were diagnosed as malignant, and 123 in 1099 patients (11.19%) were diagnosed as suspected. The diagnostic accuracies of terminal ileal polyp, cyst, cancer, eosinophilic enteritis, parasite, lymphofollicular hyperplasia, and amyloidosis were 100%. The diagnosis was delayed in 9.93% of Crohn's disease (CD) and 12.5% of lymphoma. Among the definite cases, the diagnosis was corrected during the follow-up in 12.5% of the patients, while the clinical treatment was corrected during the follow-up in 17.86% of the patients. Among the suspected cases, the diagnosis and treatment was corrected in 61.11% of the patients during the follow-up., Conclusion: Coincident diagnosis of ileitis and ileum ulcer is low. Delayed diagnosis of Crohn's disease and lymphoma were observed in a certain proportion of patients with terminal ileum lesions. A follow-up endoscopy was strongly recommended for these suspected patients with terminal ileum lesions., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2020 Qinglian Zhong et al.)

C57Bl6 (B6) mice devoid of glutathione peroxidases 1 and 2 (Gpx1/2-DKO) develop ileitis after weaning. We previously showed germ-free Gpx1/2-DKO mice of mixed B6.129 background did not develop ileocolitis. Here, we examine the composition of the ileitis provoking microbiota in B6 Gpx1/2-DKO mice. DNA was isolated from the ileum fecal stream and subjected to high-throughput sequencing of the V3 and V4 regions of the 16S rRNA gene to determine the abundance of operational taxonomic units (OTUs). We analyzed the role of bacteria by comparing the microbiomes of the DKO and pathology-free non-DKO mice. Mice were treated with metronidazole, streptomycin, and vancomycin to alter pathology and correlate the OTU abundances with pathology levels. Principal component analysis based on Jaccard distance of abundance showed 3 distinct outcomes relative to the source Gpx1/2-DKO microbiome. Association analyses of pathology and abundance of OTUs served to rule out 7-11 of 24 OTUs for involvement in the ileitis. Collections of OTUs were identified that appeared to be linked to ileitis in this animal model and would be classified as commensals. In Gpx1/2-DKO mice, host oxidant generation from NOX1 and DUOX2 in response to commensals may compromise the ileum epithelial barrier, a role generally ascribed to oxidants generated from mitochondria, NOX2 and endoplasmic reticulum stress in response to presumptive pathogens in IBD. Elevated oxidant levels may contribute to epithelial cell shedding, which is strongly associated with progress toward inflammation in Gpx1/2-DKO mice and predictive of relapse in IBD by allowing leakage of microbial components into the submucosa., (© 2020 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.)

Crohn's disease (CD) patients can be grouped into patients suffering from ileitis, ileocolitis, jejunoileitis, and colitis. The pathophysiological mechanism underlying this regional inflammation is still unknown. Although most murine models of inflammatory bowel disease (IBD) develop inflammation in the colon, there is an unmet need for novel models that recapitulate the spontaneous and fluctuating nature of inflammation as seen in CD. Recently, mice with an intestinal epithelial cell-specific deletion for Caspase-8 (Casp8ΔIEC mice), which are characterized by cell death-driven ileitis and disrupted Paneth cell homeostasis, have been identified as a novel model of CD-like ileitis. Here we uncovered that genetic susceptibility alone is sufficient to drive ileitis in Casp8ΔIEC mice. In sharp contrast, environmental factors, such as a disease-relevant microbial flora, determine colonic inflammation. Accordingly, depending on the microbial environment, isogenic Casp8ΔIEC mice either exclusively developed ileitis or suffered from pathologies in several parts of the gastrointestinal tract. Colitis in these mice was characterized by massive epithelial cell death, leading to spread of commensal gut microbes to the extra-intestinal space and hence an aberrant activation of the systemic immunity. We further uncovered that Casp8ΔIEC mice show qualitative and quantitative changes in the intestinal microbiome associated with an altered mucosal and systemic immune response. In summary, we identified that inflammation in this murine model of CD-like inflammation is characterized by an immune reaction, presumably directed against a disease-relevant microbiota in a genetically susceptible host, with impaired mucosal barrier function and bacterial clearance at the epithelial interface., (© 2019 Crohn’s & Colitis Foundation. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background & Aims: Interferon lambda (IFNL) is expressed at high levels by intestinal epithelial cells (IECs) and mucosal immune cells in response to infection and inflammation. We investigated whether IFNL might contribute to pathogenesis of Crohn's disease (CD)., Methods: We obtained serum samples and terminal ileum biopsies from 47 patients with CD and 16 healthy individuals (controls). We measured levels of IFNL by enzyme-linked immunosorbent assay and immunohistochemistry and location of expression by confocal microscopy. Activation of IFNL signaling via STAT1 was measured in areas of no, mild, moderate, and severe inflammation and correlated with Paneth cell homeostasis and inflammation. IFNL expression and function were studied in wild-type mice and mice with intestinal epithelial cell-specific (ΔIEC) disruption or full-body disruption of specific genes (Mlkl -/- , Stat1 ΔIEC , Casp8 ΔIEC , Casp8 ΔIEC Ripk3 -/- , Casp8 ΔIEC Tnfr -/- , Casp8 ΔIEC Mlkl -/- , and Nod2 -/- mice). Some mice were given tail vein injections of a vector encoding a secreted form of IFNL. Intestinal tissues were collected from mice and analyzed by immunohistochemistry and immunoblots. We generated 3-dimensional small intestinal organoids from mice and studied the effects of IFNL and inhibitors of STAT-signaling pathway., Results: Patients with CD had significant increases in serum and ileal levels of IFNL compared with controls. Levels of IFNL were highest in ileum tissues with severe inflammation. High levels of IFNL associated with a reduced number of Paneth cells and increased cell death at the crypt bottom in inflamed ileum samples. Intestinal tissues from the ileum of wild-type mice injected with a vector expressing IFNL had reduced numbers of Paneth cells. IFNL-induced death of Paneth cells in mice did not occur via apoptosis, but required Mixed Lineage Kinase Domain Like (MLKL) and activation of Signal transducer and activator of transcription 1 (STAT1). In organoids, inhibitors of Janus kinase (JAK) signaling via STAT1 (glucocorticoids, tofacitinib, or filgotinib) reduced expression of proteins that mediate cell death and prevented Paneth cell death., Conclusions: Levels of IFNL are increased in serum and inflamed ileal tissues from patients with CD and associated with a loss of Paneth cells. Expression of a secreted form of IFNL in mice results in loss of Paneth cells from intestinal tissues, via STAT1 and MLKL, controlled by caspase 8. Strategies to reduce IFNL or block its effects might be developed for treatment of patients with CD affecting the terminal ileum., (Copyright © 2019 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Purpose of Review: Not all injuries of the terminal ileum are Crohn's disease. It is the purpose of this review to consider the differential diagnosis of other acute and chronic ileal lesions., Recent Findings: The recognition of a granulomatous disease of the terminal ileum, distinct from tuberculosis, dates back over 85 years and perhaps much farther, but over the past decades, many other clinical pathologic entities have been described that are neither tuberculosis nor Crohn's eponymous regional enteritis. In recent years, the catalog of lesions mimicking Crohn's disease of the small bowel and proposals for differential diagnosis and treatment have expanded to include newly reported appendiceal pathology, primary cancers and lymphomas of the intestine, unexpected metastases from distant organs, unusual infections, vasculitides and other ischemic conditions, Behçet's disease, endometriosis, and drug reactions. A diagnosis of Crohn's disease should not be a reflex action in the face of small bowel structural or inflammatory lesions without consideration of pathology in adjacent organs, primary and metastatic lesions of the small intestine, infections, vascular diseases, infiltrative diseases, drug injury, or other "idiopathic" conditions.

Death receptor 3 (DR3), a member of the tumor necrosis factor receptor (TNFR) superfamily, has been implicated in regulating T-helper type-1 (T H 1), type-2 (T H 2), and type-17 (T H 17) responses as well as regulatory T cell (T reg ) and innate lymphoid cell (ILC) functions during immune-mediated diseases. However, the role of DR3 in controlling lymphocyte functions in inflammatory bowel disease (IBD) is not fully understood. Recent studies have shown that activation of DR3 signaling modulates T reg expansion suggesting that stimulation of DR3 represents a potential therapeutic target in human inflammatory diseases, including Crohn's disease (CD). In this study, we tested a specific DR3 agonistic antibody (4C12) in SAMP1/YitFc (SAMP) mice with CD-like ileitis. Interestingly, treatment with 4C12 prior to disease manifestation markedly worsened the severity of ileitis in SAMP mice despite an increase in FoxP3 + lymphocytes in mesenteric lymph node (MLN) and small-intestinal lamina propria (LP) cells. Disease exacerbation was dominated by overproduction of both T H 1 and T H 2 cytokines and associated with expansion of dysfunctional CD25 - FoxP3 + and ILC group 1 (ILC1) cells. These effects were accompanied by a reduction in CD25 + FoxP3 + and ILC group 3 (ILC3) cells. By comparison, genetic deletion of DR3 effectively reversed the inflammatory phenotype in SAMP mice by promoting the expansion of CD25 + FoxP3 + over CD25 - FoxP3 + cells and the production of IL-10 protein. Collectively, our data demonstrate that DR3 signaling modulates a multicellular network, encompassing T regs , T effectors, and ILCs, governing disease development and progression in SAMP mice with CD-like ileitis. Manipulating DR3 signaling toward the restoration of the balance between protective and inflammatory lymphocytes may represent a novel and targeted therapeutic modality for patients with CD.

Background/aim: Pediatric ileocolonic Crohn disease (CD) may be difficult to distinguish from ulcerative colitis (UC) with backwash ileitis (BWI). The primary aim of the study was to determine the probability of CD in children with a confluent colitis and ileitis when newly diagnosed with inflammatory bowel disease (IBD)., Methods: A retrospective observational study of 100 newly diagnosed patients with IBD was performed. Two pathologists reviewed ileal biopsy specimens for 8 histological features. Biopsy and clinical features were evaluated for predictive ability of a final diagnosis of CD., Results: The presence of crypt distortion, lamina propria (LP) expansion, and acute LP inflammation combined with 4 clinical variables in multivariate regression analysis had adequate discriminative validity when comparing the mean probability of a final CD diagnosis between CD and not-CD groups (0.90 vs. 0.59, p value <0.001). When crypt distortion, LP expansion, and acute LP inflammation are present in any combination, the sensitivity and specificity for presence of CD ranges 38.4-57% and 92.9-100%, respectively., Conclusions: Combining histological features of ileitis and clinical variables can adequately discriminate between the presence and absence of Crohn disease in children who present with confluent colitis and ileitis. Combined presence of certain histological features has high specificity for CD., (Copyright © 2017 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.)

Background: Approximately 10% of Crohn's disease (CD) patients have this disease affecting the small bowel (SB) beyond the reach of Ileo-colonoscopy. Capsule endoscopy (SBCE) is the recommended investigation for SB disease. An accurate and inexpensive biomarker would help identify at-risk patients., Aim: To examine the efficacy of faecal calprotectin (FC) and C-reactive protein (CRP) as predictors of SBCE findings in suspected and known CD., Methods: A prospective observational study. Consecutive patients referred for SBCE gave FC and CRP samples. The diagnostic accuracy for SB CD based on SBCE result was calculated for both FC and CRP., Results: Of 100 invitees, FC and SBCE results were available in 64 cases. Correlation between FC >50 µg/g and SBCE result was poor К = 0.163; sensitivity, specificity, positive predictive value (PPV) and negative predictive values for ileitis were 60, 61, 32 and 83% respectively. PPV and specificity improved at FC >100 µg/g, 76 and 40%, correlation remained fair, К = 0.259. Receiver operating characteristic analysis had a sensitivity of 47% and specificity of 90% for FC >194 µg/g. CRP alone or in combination was an inaccurate predictor of ileitis., Conclusion: Our study suggests that FC level >194 µg/g may be a useful SBCE filter test, identifying patients at risk of SB CD., (© 2018 S. Karger AG, Basel.)

CD4 + T cells are tightly regulated by microbiota in the intestine, but whether intestinal T cells interface with host-derived metabolites is less clear. Here, we show that CD4 + T effector (Teff) cells upregulated the xenobiotic transporter, Mdr1, in the ileum to maintain homeostasis in the presence of bile acids. Whereas wild-type Teff cells upregulated Mdr1 in the ileum, those lacking Mdr1 displayed mucosal dysfunction and induced Crohn's disease-like ileitis following transfer into Rag1 -/- hosts. Mdr1 mitigated oxidative stress and enforced homeostasis in Teff cells exposed to conjugated bile acids (CBAs), a class of liver-derived emulsifying agents that actively circulate through the ileal mucosa. Blocking ileal CBA reabsorption in transferred Rag1 -/- mice restored Mdr1-deficient Teff cell homeostasis and attenuated ileitis. Further, a subset of ileal Crohn's disease patients displayed MDR1 loss of function. Together, these results suggest that coordinated interaction between mucosal Teff cells and CBAs in the ileum regulate intestinal immune homeostasis., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Purpose: It is not clear whether aspecific ileitis may represent an early manifestation or a milder variant of Crohn's disease or not. The aim of this study was to evaluate the clinical outcomes of aspecific ileitis., Methods: Subjects with at least one of the following signs at retrograde ileoscopy: erythema, nodularity, aftae, erosions, and ulcers were considered. They should not have had defined gastrointestinal disease, biochemical signs of inflammation, use of drugs, celiac disease, and intestinal infectious disease., Results: We enrolled 51 subjects (22 men), mean age (± SD) at colonoscopy of 41.1 ± 13.1 years. Indications to colonoscopy were overt or occult intestinal bleeding (18), diarrhoea (15), systemic signs (10), IBS-like symptoms (5), other (3). Ileal lesions were ulcers (9), erosions (26), aftae (10), nodularity (3), and erythema (3). At histological evaluation aspecific findings were observed. Forty-four out of 51 (86.3%) subjects underwent further investigations of small bowel. Second colonoscopy was performed in 31 (60.8%) persisting symptomatic subjects: ileitis was confirmed in 14 (46.6%). Ten out of 51 (19.6%) were eventually diagnosed as affected by Crohn's disease., Conclusions: A substantial proportion of subjects with endoscopic and histological findings of aspecific ileitis is eventually diagnosed as affected by Crohn's disease. In these subjects, a strict follow-up is strongly recommended.

Background: Capsule endoscopy (CE) has proven to be highly effective at detecting small bowel lesions, but studies regarding the diagnostic impact of CE on ileitis are rare., Aims: We evaluated the diagnostic value of small bowel CE for isolated ileitis observed during ileocolonoscopy., Methods: The CE results in 137 patients initially diagnosed with ileitis without colonic mucosal abnormalities on ileocolonoscopy at one of eight tertiary referral centers between October 2002 and June 2015 were retrospectively analyzed., Results: Among the 137 patients with isolated ileitis observed on ileocolonoscopy, 117 (85.4%) revealed positive small bowel CE findings (85.4%). The rate of positive small bowel CE findings was 92.9% in cases of ileal aphthous ulcer or erosion, and 90.9% in cases of ileal ulcer. Among 117 positive CE cases, the most common final diagnosis by CE was Crohn's disease (CD) (n = 44, 32%). No findings were identified in 20 (14.6%) of 137 cases. Ileal erosion/ulcer, rather than findings such as nodularity and erythema or elevated erythrocyte sedimentation rate (ESR) (>10 mm/h), was significant predictive factors for positive CE findings in multivariate analysis., Conclusions: Small bowel CE showed a high diagnostic yield (85.4%) in symptomatic patients with isolated ileitis on ileocolonoscopy. Erosion or ulcer of the small bowel was a common finding on CE (66.4%), and approximately one-third of patients were diagnosed with CD. In patients with isolated ileitis on ileocolonoscopy, CE should be considered to evaluate small bowel lesions when the patient shows an elevated ESR or when the ileitis manifests as ileal ulcer or erosion rather than a nodular or erythematous lesion.

Background: Primary sclerosing cholangitis (PSC) is associated with ulcerative colitis and extensive colonic involvement or ileocolitis in Crohn's disease (CD). To our knowledge, no specific report of isolated ileitis associated with PSC in CD patients has been published in CD patients., Aim and Methods: We report three cases of patients with isolated Crohn's ileitis associated with PSC and in whom colonic inflammation was never documented., Results: Patients were followed up 10-23 years and each patient underwent 6-7 ileocolonoscopies: inflammation was located only in the terminal ileum, which was confirmed on surgical specimens in two patients. Small-duct PSC led to diagnosis of CD ileitis in one patient, while small and large-ducts PSC were evidenced after CD diagnosis in the other 2. PSC were regularly followed for 9-10 years., Conclusions: Our three cases of PSC with isolated CD ileitis and long-term follow-up without any sign of colonic involvement argue against the concept that colonic mucosal inflammation is critical for the pathogenesis of PSC in inflammatory bowel disease.

Aims: Histological features of chronic active ileitis in the small intestine neighbouring a Meckel's diverticulum raise the possibility of concurrent Crohn's disease. Several studies have reported a significant association between Meckel's diverticulum and Crohn's disease, whereas some case reports have proposed that the ileitis is attributable to acid-secreting gastric heterotopia. The aim of this study was to evaluate the incidence, histomorphology and clinical follow-up of Meckel's diverticulum-associated ileitis., Methods and Results: Medical records and slides from 48 consecutive surgical resections performed for Meckel's diverticulum were reviewed. Nine of 48 adults had significant inflammatory changes in the small intestine neighbouring the diverticulum. Two were transmural ulcers attributable to ingestion of a sharp object. Two patients had established Crohn's disease, both with long segments (>95 mm) of transmural inflammation located >100 mm from the diverticulum. The remaining five patients had inflammatory changes (ulceration, pseudopyloric metaplasia, submucosal fibrosis, and muscularis mucosa hyperplasia) confined to a short segment (<20 mm) of mucosa/submucosa within 50-60 mm of the diverticulum. Two had gastric heterotopia in the diverticulum. None of these five patients used non-steroidal anti-inflammatory drugs (NSAIDs). On follow-up, none had symptoms, imaging or pathology suggestive of Crohn's disease., Conclusions: Ileitis affecting a short segment of mucosa and submucosa in the small intestine near a Meckel's diverticulum is relatively common, and is not necessarily related to Crohn's disease., (© 2015 John Wiley & Sons Ltd.)

Tumor necrosis factor α (TNFα) is a key pathogenic factor in Crohn's disease and rheumatoid arthritis. TNF(ΔARE) mice express high levels of TNFα and present Crohn's-like ileitis and arthritis. Alterations in the chemokine network could underline the TNF-driven ileitis. The aim of this study was to evaluate the role of TNF and chemokines in ileitis using ectromelia virus cytokine response modifier D (CrmD), a protein that binds TNFα and a limited number of chemokines. We generated transgenic mice expressing CrmD in intestinal epithelial cells (vCrmD mice) and crossed them with the TNF(ΔARE) mice to test whether CrmD could affect TNF-driven inflammatory processes. During homeostasis, only the number of B cells in the lamina propria was reduced by CrmD expression. Interestingly, CrmD expression in the intestine markedly attenuated the inflammatory infiltrates in the ileum of TNF(ΔARE) mice, but did not affect development of arthritis. Our results suggest that CrmD affects development of ileitis by locally affecting both TNF and chemokine function in the ileum.

Background: Surveillance of intestinal cancer in Crohn's disease (CD) has often been advocated. To date, no clear evidence exists whether CD patients are at special risk for intestinal cancer. An increased incidence of small bowel adenocarcinoma is suggested. However, recent figures also suggest an increased risk of CD associated colorectal cancer. We report our experience with 10 cases of CD complicated by intestinal adenocarcinoma., Materials and Methods: Our institutional database included 330 patients treated for CD between 1988-2005. Data of patients that developed carcinoma within Crohn's lesions of either small or large bowel were analyzed., Results: Ten patients were diagnosed with CD complicated by carcinoma. In nine patients, cancer was present in the colorectum and in one, in Crohn's ileitis. Tumors were in conjunction with fistulae in three and developed within strictures in five patients. Mean age at the time of diagnosis of CD was 43 years. Mean duration of CD until diagnosis of cancer was 14 years. Only five patients were diagnosed for cancer preoperatively. Staging revealed advanced tumors in almost all patients. Mean survival after surgery was 29 months (2-149 months)., Conclusions: Cancer risk in CD and especially in Crohn's colitis may still be underestimated. Delayed diagnosis resulted in a poor prognosis. The value of colonoscopy as surveillance tool is questioned by the fact that in our patients, carcinoma was diagnosed in some patients preoperatively by routine colonoscopy. Therefore, additional markers should be identified to detect CD patients at risk.

Background: There have been conflicting results regarding the effect of Crohn's disease on the neurochemical composition of the enteric nervous system., Aims: To examine the effect of Crohn's disease on the neurochemical composition of enteric nerve fibres and cell bodies using whole mount preparations of human ileum., Methods: Whole wall ileum from seven normal subjects and nine patients with Crohn's disease was used to investigate the neurochemical composition of neurones and nerve fibres in the myenteric plexus, circular muscle, and serosa layer of ileum using immunohistochemical techniques., Results: Increased tyrosine hydroxylase, 5-hydroxytryptamine, and neuropeptide Y immunoreactivity was exclusively seen in the myenteric plexus. There was increased neurofilament immunoreactivity in the myenteric plexus and nerve fibres of the circular muscle layer, and thick bundles of immunoreactive nerve fibres in the serosa layer. Increased vasoactive intestinal polypeptide, nitric oxide synthase, and pituitary adenylate cyclase activating peptide immunoreactivity was seen in the myenteric plexus and nerve fibres of the circular muscle layer, and aggregates of inflammatory cells in the serosa layer of the afflicted segment of Crohn's ileum. In addition, there was a chaotic display of nerve fibres containing some of the neuroactive substances with a high frequency of enlarged varicosities in the myenteric ganglia and/or nerve fibres of the circular muscle layer of Crohn's ileum., Conclusion: Results show quantitative as well as qualitative changes in the neurochemical composition of enteric nerve fibres and nerve cell bodies of Crohn's ileum. These changes and the presence of nitric oxide synthase and peptides immunoreactive inflammatory cells in the serosa layer suggest that nerve-immune interactions may have a significant role in the process of the inflammatory changes seen in Crohn's ileitis.

Seventeen children with active Crohn's disease of the small intestine were entered into a randomised control trial comparing the efficacy of an elemental diet with that of a high dose steroid regimen. Eight children received an elemental diet (Flexical) through a nasogastric tube for six weeks, followed by reintroduction of food over six weeks during which the Flexical was stopped. Seven children were given intramuscular adrenocorticotrophic hormone followed by oral prednisolone with sulphasalazine. Two children were withdrawn from the trial. The elemental diet was equally effective in inducing an improvement in Lloyd-Still disease activity index, erythrocyte sedimentation rate, C reactive protein and albumin concentrations, and body weight as the high dose steroid regimen. Linear growth, assessed from height velocity over six months, was significantly greater in the children receiving an elemental diet.