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Summary: Background: The involvement of Mediterranean fever (MEFV) gene mutations in patients with inflammatory bowel disease unclassified (IBDU) remains unclear. This study aimed to determine the clinical characteristics and responsiveness to colchicine in Japanese patients with IBDU carrying MEFV mutations. Methods: In this retrospective cohort study, we examined MEFV mutations using gene analysis, clinical information, and colchicine responsiveness. Furthermore, we examined cytokine production in exon 2-mutated THP-1 cells (a monocytic cell line) and microbiome analysis. Findings: Of the 396 patients diagnosed with IBDU, 60.1% had MEFV mutations. Exon 2 mutations were the most common (83.7%). Among patients with available clinical information, 43.3% of patients with IBDU had typical Familial Mediterranean fever (FMF). The efficacy of colchicine in patients with IBDU carrying MEFV mutations was 84.6%. Significant differences were noted in the production of inflammatory; cytokines between THP-1 cells with and without MEFV mutations. Microbial compositions differed between patients with IBDU carrying MEFV mutations and patients with IBD and healthy controls. Interpretation: Patients with IBDU carrying MEFV mutations responded well to colchicine treatment. A notable subset of patients met the criteria for typical FMF. Alterations in intestinal microbiota may contribute to disease pathogenesis. Funding: This work was supported by the Japan Agency for Medical Research and Development (21ek0410057h0003), a grant from the Uehara Memorial Foundation, and the Health and Labour Sciences Research Grants for research on intractable diseases from the Ministry of Health, Labour and Welfare (MHLW) of Japan (Investigation and Research for Intractable Inflammatory Bowel Disease; Grant Number 20316729).

Purpose: Few studies have reported the prevalence of inflammatory bowel disease unclassified (IBDU) among Korean pediatric IBD (PIBD) population. To address this gap, we used two tertiary centers and nationwide population-based healthcare administrative data to estimate the prevalence of Korean pediatric IBDU at the time of diagnosis. Methods: We identified 136 patients aged 2-17 years with newly diagnosed IBD (94 Crohn's disease [CD] and 42 ulcerative colitis [UC]) from two tertiary centers in Korea between 2005 and 2017. We reclassified these 136 patients using the revised Porto criteria. To estimate the population-based prevalence, we analyzed Korean administrative healthcare data between 2005 and 2016, which revealed 3,650 IBD patients, including 2,538 CD and 1,112 UC. By extrapolating the reclassified results to a population-based dataset, we estimated the prevalence of PIBD subtypes. Results: Among the 94 CD, the original diagnosis remained unchanged in 93 (98.9%), while the diagnosis of one (1.1%) patient was changed to IBDU. Among the 42 UC, the original diagnosis remained unchanged in 13 (31.0%), while the diagnoses in 11 (26.2%), 17 (40.5%), and one (2.4%) patient changed to atypical UC, IBDU, and CD, respectively. The estimated prevalences of CD, UC, atypical UC, and IBDU in the Korean population were 69.5%, 9.4%, 8.0%, and 13.1%, respectively. Conclusion: This study is the first in Korea to estimate the prevalence of pediatric IBDU. This prevalence (13.1%) aligns with findings from Western studies. Large-scale prospective multicenter studies on PIBDU are required to examine the clinical features and outcomes of this condition. [ABSTRACT FROM AUTHOR]

Abstract Background Approximately 10-15% of inflammatory bowel disease (IBD) patients with overlapping features of ulcerative colitis (UC) and Crohn’s disease (CD) are termed as inflammatory bowel disease unclassified (IBDU). This study aimed to describe the clinical features of IBDU and evaluate the potential associated factors of reclassification. Methods The clinical data of 37 IBDU patients were retrospectively analyzed from November 2012 to November 2020. 74 UC and 74 CD patients were randomly selected and age- and sex-matched with the 37 IBDU patients. Clinical characteristics were compared between the three patient groups. Potential factors associated with the IBDU reclassification were evaluated. Results 60% of IBDU patients displayed rectal-sparing disease, and 70% of them displayed segmental disease. In comparison to UC and CD, the IBDU group demonstrated higher rates of gastrointestinal bleeding (32.4%), intestinal perforation (13.5%), spontaneous blood on endoscopy (51.4%), and progression (56.8%). The inflammation proceeded relatively slowly, manifesting as chronic alterations like pseudopolyps (78.4%) and haustra blunt or disappearance (56.8%). 60% of IBDU patients exhibited crypt abscess, and 16.7% of them exhibited fissuring ulcers or transmural lymphoid inflammation. The proportions of IBDU patients receiving immunosuppressants, surgery, and infliximab were basically the same as those of CD patients. During the 79 (66, 91) months of follow-up, 24.3% of IBDU patients were reclassified as UC, while 21.6% were reclassified as CD. The presence of intestinal hemorrhaging was associated with CD reclassification, while hypoalbuminemia was associated with UC reclassification. Conclusions IBDU may evolve into UC or CD during follow-up, and hemorrhage was associated with CD reclassification. Different from the other two groups, IBDU exhibited a more acute onset and a gradual progression. When an IBD patient presents with transmural inflammation or crypt abscess but lacks transmural lymphoid aggregates or fissuring ulcers, the diagnosis of IBDU should be considered.

Background: Approximately 10-15% of inflammatory bowel disease (IBD) patients with overlapping features of ulcerative colitis (UC) and Crohn's disease (CD) are termed as inflammatory bowel disease unclassified (IBDU). This study aimed to describe the clinical features of IBDU and evaluate the potential associated factors of reclassification. Methods: The clinical data of 37 IBDU patients were retrospectively analyzed from November 2012 to November 2020. 74 UC and 74 CD patients were randomly selected and age- and sex-matched with the 37 IBDU patients. Clinical characteristics were compared between the three patient groups. Potential factors associated with the IBDU reclassification were evaluated. Results: 60% of IBDU patients displayed rectal-sparing disease, and 70% of them displayed segmental disease. In comparison to UC and CD, the IBDU group demonstrated higher rates of gastrointestinal bleeding (32.4%), intestinal perforation (13.5%), spontaneous blood on endoscopy (51.4%), and progression (56.8%). The inflammation proceeded relatively slowly, manifesting as chronic alterations like pseudopolyps (78.4%) and haustra blunt or disappearance (56.8%). 60% of IBDU patients exhibited crypt abscess, and 16.7% of them exhibited fissuring ulcers or transmural lymphoid inflammation. The proportions of IBDU patients receiving immunosuppressants, surgery, and infliximab were basically the same as those of CD patients. During the 79 (66, 91) months of follow-up, 24.3% of IBDU patients were reclassified as UC, while 21.6% were reclassified as CD. The presence of intestinal hemorrhaging was associated with CD reclassification, while hypoalbuminemia was associated with UC reclassification. Conclusions: IBDU may evolve into UC or CD during follow-up, and hemorrhage was associated with CD reclassification. Different from the other two groups, IBDU exhibited a more acute onset and a gradual progression. When an IBD patient presents with transmural inflammation or crypt abscess but lacks transmural lymphoid aggregates or fissuring ulcers, the diagnosis of IBDU should be considered. [ABSTRACT FROM AUTHOR]

Inflammatory bowel disease unclassified (IBDU) is referred to as colitis that has clinical characteristics related to inflammatory bowel disease, but cannot be clearly determined or classified as either ulcerative colitis (UC) or Crohn’s disease (CD) clinically. Over time, most patients with IBDU can be finally diagnosed as either UC or CD. Treatment of IBDU should follow a step-up strategy. This article describes the clinical characteristics, diagnosis and treatment of IBDU.

Familial Mediterranean fever (FMF) in gastrointestinal involvement has been considered rare, but resent reports suggest that FMF causes enterocolitis which is similar endoscopic findings to inflammatory bowel disease. The clinical characteristics and endoscopic findings of FMF with enterocolitis remain unclear. Here, we report a case of an FMF patient who had enterocolitis with stricture of the terminal ileum whose endoscopic and clinical features mimicked Crohn's disease. A 23-year-old man who was diagnosed with FMF 10 years ago presented with abdominal pain and diarrhea. Colonoscopy showed terminal ileitis and aphthous colitis; however, these findings, including the histopathology, did not confirm Crohn's disease. Therefore, we diagnosed FMF with enterocolitis and administered anti-interleukin-1β monoclonal antibody (canakinumab). The patient's symptoms improved with treatment, but after 1 year, lower abdominal pain recurred. Colonoscopy revealed a stricture of the terminal ileum. Endoscopic balloon dilation relieved his symptoms. At present, he has been followed up without surgical treatment by endoscopic balloon dilation every 6 month. Clinicians should be aware that FMF accompanied with enterocolitis may resemble Crohn's disease. [ABSTRACT FROM AUTHOR]

Background and Aims: Familial mediterranean fever (FMF), an autoinflammatory disease, is characterized by periodic fever and serositis. An MEFV gene mutation has been identified as the cause of FMF. Recently, patients with MEFV gene mutations and chronic gastrointestinal mucosal inflammation mimicking inflammatory bowel disease (IBD) have been reported. In this retrospective study, we analyzed the clinical characteristics of patients with IBD unclassified (IBDU) with MEFV gene mutations. Methods:MEFV gene analysis was performed on 8 patients with IBDU among 710 patients with IBD who had been treated at Kyorin University Hospital from April 2016 to December 2018. Clinical manifestations, endoscopic findings, and serological markers were also analyzed. Results: The average of the 8 patients with IBDU (3 men, 5 women) was 32.7 ± 6.4 years (range 26–76 years). Their symptoms comprised diarrhea (n = 8, 100%), hematochezia (n = 3, 37.5%), abdominal pain (n = 3, 37.5%), high fever (n = 2, 16.5%), and other periodic symptoms (n = 2, 16.5%). MEFV gene mutation was confirmed in 4/8 of these patients. Colonoscopy showed various mucosal lesions, rectal sparing, right side dominant colitis, pseudopolyposis, and granular protrusions. Colchicine was administered to 5 of the 8 patients (4 with and 1 without MEFV mutation) who were resistant to conventional treatment for ulcerative colitis. Clinical and endoscopic improvement was observed in all of 5 patients treated with colchicine. Conclusions: Some patients diagnosed as having IBDU have enterocolitis related to MEFV gene mutation and respond to colchicine therapy. [ABSTRACT FROM AUTHOR]

Objectives: This study aims to characterize pediatric inflammatory bowel disease (IBD) patients who change diagnosis and describe the characteristics of that change., Methods: A retrospective study was conducted on pediatric IBD patients from the ImproveCareNow (ICN) multicenter international cohort from 2007 to January 2019. Primary outcome was change in diagnosis after the first four visits. Other variables included demographics, diagnostics, disease characteristics, and timing., Results: 6.1% of 18,055 patients aged 1-20 years changed diagnosis. Median time between the baseline visit and first diagnosis change was 0.9 years. Change in diagnosis occurred in 257/12,178 (2.1%) patients with Crohn's disease (CD), 347/4758 (7.3%) patients with ulcerative colitis (UC), and 495/1119 (44.2%) patients with IBD-Unclassified (IBD-U). In multivariable analysis, initial diagnosis of IBD-U and longer follow-up times were associated with greater odds of a diagnosis change., Conclusion: IBD-U initial diagnosis and longer follow-up were associated with increased diagnosis change risk. The most common change was reclassification to CD. Disease activity, moderate malnutrition, and presence of EIMs were not associated with change in diagnosis., (© 2024 European Society for Pediatric Gastroenterology, Hepatology, and Nutrition and North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition.)

Background: Despite advancements in medical therapy for ulcerative colitis (UC), a significant proportion of children progress to colectomy with ileal pouch-anal anastomosis (IPAA). Procedural related complications between two- and three-stage operations in children have not been well described.Methods: We performed a retrospective review of patients who underwent a colectomy for UC or inflammatory bowel disease unclassified between 2008 and 2018.Results: Forty-nine children underwent an IPAA at the time of colectomy (two stage) or during a subsequent operation (three stage). Preoperative hemoglobin and albumin concentrations were lower among those undergoing three-stage procedures. The rate of early complications (≤30 days) was similar between the two groups (p = 0.46); however, late complications (>30 days) were more commonly associated with three-stage procedures (p = 0.03). Time with a stoma was 3.2 months longer among those who underwent a three-stage procedure. While three-stage procedures were more often performed during the first half of the study period (2008-2012), two-stage procedures became more common during the second half (2013-2018). During this transition to favor two-stage procedures, complication rates did not significantly change.Conclusion: Although three-stage procedures were thought to be associated with fewer complications, we found comparable complication rates as we transition to two-stage procedures. [ABSTRACT FROM AUTHOR]

Background and Aim: A definitive diagnosis of Crohn's disease (CD) or ulcerative colitis (UC) is not always possible, and a proportion of patients will be diagnosed as inflammatory bowel disease unclassified (IBDU). The aim of the study was to investigate the prognosis of patients initially diagnosed with IBDU and the disease course during the following 5 years. Methods: The Epi‐IBD study is a prospective population‐based cohort of 1289 IBD patients diagnosed in centers across Europe. Clinical data were captured prospectively throughout the follow‐up period. Results: Overall, 476 (37%) patients were initially diagnosed with CD, 701 (54%) with UC, and 112 (9%) with IBDU. During follow‐up, 28 (25%) IBDU patients were changed diagnoses to either UC (n = 20, 71%) or CD (n = 8, 29%) after a median of 6 months (interquartile range: 4–12), while 84 (7% of the total cohort) remained IBDU. A total of 17 (15%) IBDU patients were hospitalized for their IBD during follow‐up, while 8 (7%) patients underwent surgery. Most surgeries (n = 6, 75%) were performed on patients whose diagnosis was later changed to UC; three of these colectomies led to a definitive diagnosis of UC. Most patients (n = 107, 96%) received 5‐aminosalicylic acid, while 11 (10%) patients received biologicals, of whom five remained classified as IBDU. Conclusions: In a population‐based inception cohort, 7% of IBD patients were not given a definitive diagnosis of IBD after 5 years of follow‐up. One in four patients with IBDU eventually was classified as CD or UC. Overall, the disease course and medication burden in IBDU patients were mild. [ABSTRACT FROM AUTHOR]

Aim: To investigate inflammatory bowel disease (IBD) register-based subtype classifications over a patient's disease course and over time. Methods: We examined International Classification of Diseases coding in patients with ≥2 IBD diagnostic listings in the National Patient Register 2002-2014 (n = 44,302). Results: 18% of the patients changed diagnosis (17% of adults, 29% of children) during a median follow-up of 3.8 years. Of visits with diagnoses of Crohn's disease (CD) or ulcerative colitis (UC), 97% were followed by the same diagnosis, whereas 67% of visits with diagnosis IBD-unclassified (IBD-U) were followed by another IBD-U diagnosis. Patients with any diagnostic change changed mostly once (47%) or twice (31%), 39% from UC to CD, 33% from CD to UC and 30% to or from IBD-U. Using a classification algorithm based on the first two diagnoses ('incident classification'), suited for prospective cohort studies, the proportion adult patients with CD, UC, and IBD-U 2002-2014 were 29%, 62%, and 10% (43%, 45%, and 12% in children). A classification model incorporating additional information from surgeries and giving weight to the last 5 years of visits ('prevalent classification'), suited for description of a study population at end of follow-up, classified 31% of adult cases as CD, 58% as UC and 11% as IBD-U (44%, 38%, and 18% in children). Conclusions: IBD subtype changed in 18% during follow-up. The proportion with CD increased and UC decreased from definition at start to end of follow-up. IBD-U was more common in children. [ABSTRACT FROM AUTHOR]

Aim There has been at least a twofold increase in the incidence of paediatric inflammatory bowel disease ( PIBD) over the last 20 years; we report the presenting features from 2010 to 2013 and compare with previous data. Methods All patients diagnosed with PIBD at University Hospitals Southampton from 2010 to 2013 were identified from an in-house database. Data were obtained from paper and electronic notes. Height, weight and BMI SDS are presented as median values (95% CI). Results One hundred and seventy-two patients were included (median age at diagnosis 13.5, 115 male); Crohn's disease ( CD) - 107, UC - 50, inflammatory bowel disease unclassified ( IBDU) - 15. The most common presenting features of CD were abdominal pain (86%), diarrhoea (78.5%) and weight loss (56.1%); 42.1% of patients had all three. In UC blood in stool (92%), diarrhoea (92%) and abdominal pain (88%) were the most common; all three in 76% of patients. CD presented with ileocolonic disease in 52.5%. UC presented with pancolitis in 64%. There was growth delay in CD: height −0.37 (−0.60 to −0.14); weight −1.09 (−1.35 to −0.83). Growth was maintained in UC: height 0.53 (0.19 to 0.87); weight 0.14 (−0.20 to 0.48). Conclusion Paediatric inflammatory bowel disease phenotype remains as extensive despite increasing incidence. Although the classical phenotype is common, a reasonable proportion present with atypical features, normal growth and normal blood markers. [ABSTRACT FROM AUTHOR]

Objective. To compare prospectively the diagnostic accuracy of magnetic resonance imaging (MRI) without use of contrast medium orally or intravenously (plain MRI) with magnetic resonance follow-through (MRFT) in patients with inflammatory bowel disease (IBD). Material and methods. Plain MRI was carried out in addition to MRFT, to which the patients were referred. All patients underwent both examinations on the same day. For the evaluation, the bowel was divided into nine segments. Two radiologists, blinded to clinical findings, evaluated bowel wall thickness, diffusion weighted imaging (DWI), and other inflammatory changes in each bowel segments. Further, hyperenhancement of the bowel was also evaluated in MRFT. Results. A total of 100 patients (40 males and 60 females; median age: 38.5; range: 19-90) were enrolled; 44 with Crohn's disease (CD), 25 with ulcerative colitis (UC), 24 with IBD unclassified (IBD-U), and 7 had other diagnosis. Sensitivity, specificity, and accuracy in CD ranged 50-86%, 93-94%, and 91-92% for wall thickening and 49-82%, 85-93%, and 84-89% for DWI, respectively. Sensitivity, specificity, and accuracy in UC range 0-40%, 87-100%, and 80-100% for wall thickening and 0-52%, 83-94% and 76-92% for DWI, respectively. The κ values for bowel wall thickening, DWI, and mural hyperenhancement were detected with fair agreement (κ = 0.26-0.39) at both MRI examinations, whereas only bowel wall thickening in MRFT were detected with moderate agreement (κ = 0.47) Conclusion. Plain MRI cannot currently replace MRFT in the workup of patients with IBD. Further research on plain MRI is needed to improve the protocol. [ABSTRACT FROM AUTHOR]

Background: Recent studies have shown that patients with inflammatory bowel disease (IBD) are less likely to be infected with Helicobacter pylori compared with non-IBD patients. We aimed to study the prevalence of H. pyloripositive and H. pylori-negative gastritis in newly diagnosed children with IBD in comparison to those with non-IBD in Greece. Materials and Methods: All children who underwent first esophagogastroduodenal endoscopy between 2002 and 2011 were retrospectively included. Four groups were studied: patients with Crohn's disease (CD), ulcerative colitis (UC), IBD unclassified (IBDU), and non-IBD individuals (non-IBD). Helicobacter pylori infection was defined by positive culture or by positive histology and CLO test. Those children with negative or not available culture and only one positive test (histology or CLO) were further evaluated by urea breath test, and the positives were also included in the infected group. Results: We studied 159 patients with IBD (66 CD, 34 UC, and 59 IBDU) and 1209 patients in non-IBD individuals. Helicobacter pylori gastritis was less frequent in the IBD group (3.8% vs 13.2% in the control group, p < .001), whereas IBD patients were significantly older than non-IBD children (p < .001). Children with H. pylori-negative gastritis were 3.3 times more likely to belong in the IBD group compared with H. pylori-positive patients (p = .006). Conclusions: Occurrence of H. pylori gastritis is less frequent in children with IBD compared with controls. Our study confirms an inverse association between H. pylori and IBD. Future studies are needed to distinguish between a true protective role of H. pylori and a confounding effect due to previous antibiotic use in children with IBD. [ABSTRACT FROM AUTHOR]

Abstract: Background and aims: Focally enhanced gastritis (FEG) has been suggested as a diagnostic marker for patients with Crohn’s disease. In this study we evaluated the prevalence of FEG in children with inflammatory bowel diseases (IBD) and assessed the ability of FEG to distinguish IBD from non-IBD patients. Methods: A retrospective study of the children who underwent esophagogastroduodenal endoscopy (EGD) during 2004–2011 was performed, after excluding individuals with H. pylori infection and celiac disease. Two groups were studied: patients with IBD (IBD group, n=185) and non-IBD patients who underwent endoscopy of the upper gastrointestinal tract for various abdominal complaints (non-IBD group, n=684). Relation of FEG to age and gender was also assessed. Results: FEG was found significantly more frequently among children with IBD (35.7% vs 3.4%, respectively, p<0.001). Children with FEG were 15.4 times more likely to have IBD than to belong in the non-IBD group. All types of IBD had significantly higher frequencies of FEG compared to non-IBD individuals (Crohn's disease: 54.1%, ulcerative colitis: 21.6%, IBD unclassified: 18.4%, all three comparisons with the non-IBD group: p-values<0.001). FEG positivity was more common in females compared to males with Crohn's disease and ulcerative colitis and in children younger than 2years in the IBD-unspecified group. FEG achieved a sensitivity of 35.7% and specificity of 96.6% in distinguishing between IBD from non-IBD patients. Conclusions: FEG has significantly higher prevalence in children with IBD, particularly Crohn's disease and can be a valuable supporting finding in cases of indefinite diagnosis. [Copyright &y& Elsevier]

About 10% of patients with colitis due to inflammatory bowel disease have indeterminate colitis. Despite newer diagnostic tools, the frequency has not diminished over the past 33 years. The current preferred term among academicians is colonic inflammatory bowel disease unclassified (IBDU), although indeterminate colitis is the term endorsed for inclusion in the ICD-10 coding system. Indeterminate colitis is more frequent among children. The anti-Saccharomyces cerevisiae (ASCA) and perinuclear anti-cytoplasmic antibody (pANCA) are useful in distinguishing IBDU from ulcerative colitis and Crohn's disease. However, current serologic and genetic studies, as well as endoscopic and imaging studies lack sufficient positive predictive values to make a definite diagnosis of Crohn's colitis or ulcerative colitis. Patients with IBDU who undergo proctocolectomy with ileal pouch-anal anastomosis have more complications than patients with ulcerative colitis. Although some patients with indeterminate colitis eventually develop characteristic ulcerative colitis or Crohn's disease, a subgroup are durably indeterminate. [ABSTRACT FROM AUTHOR]

Objective: Inflammatory bowel diseases (IBDs) are idiopathic, chronic, and inflammatory intestinal disorders. The two main types, ulcerative colitis (UC) and Crohn's disease (CD), sometimes mimic each other and are not readily distinguishable. The purpose of this study was to present a series of hospitalized cases, which could not initially be classified as a subtype of IBD, and to try to note roles of the terms indeterminate colitis (IC) and inflammatory bowel disease unclassified (IBDU) when such a dilemma arises. Methods: Medical records of 477 patients hospitalized due to IBD, during the period of January 2002 to April 2009, were retrospectively studied in the present paper. All available previous biopsies from endoscopies of these patients were reanalyzed. Results: Twenty-seven of 477 IBD patients (5.7%) had been initially diagnosed as having IBDU. Of them, 23 received colonoscopy and histological examinations in our hospital. A total of 90% (9/10) and 66.7% (4/6) of patients, respectively, had a positive finding via wireless capsule endoscopy (CE) and double-balloon enteroscopy (DBE). The barium-swallow or small bowel follow-through (SBFT) was performed on 11 patients. Positive changes were observed under computer tomographic (CT) scanning in 89.5% (17/19) of patients. Reasonable treatment strategies were employed for all patients. Conclusions: Our data indicate that IBDU accounts for 5.7% of initial diagnoses of IBD. The definition of IBDU is valuable in clinical practice. For those who had no clear clinical, endoscopic, histological, or other features affording a diagnosis of either UC or CD, IBDU could be used parenthetically. [ABSTRACT FROM AUTHOR]

Background: The inflammatory bowel diseases cover a diverse range of conditions generally grouped into Crohn's disease (CD) or ulcerative colitis (UC) based on clinical, laboratory, radiological, endoscopic, and histological criteria. However, inflammatory bowel disease unclassified (IBDU) is used when there are clinical and endoscopic signs of chronic colitis without specific features of UC or CD but features of both. Conjecture exists regarding IBDU, especially in children, as to whether it represents a unique childhood phenotype or whether it reflects the difficulties in assigning an IBD subtype at an early age., Summary: This review examines the current understanding of pediatric IBDU and assesses the evidence supporting IBDU as a distinctive disease entity on the spectrum of inflammatory bowel disease., Key Messages: Pediatric-onset IBDU is more common than adult-onset IBDU. Therefore, an understanding of IBDU in this age group assumes more importance. However, there remains a paucity of information and a lack of exclusive longitudinal studies on pediatric IBDU. Subsequently there is significant disparity in the reported prevalence, clinical course, reclassification trends, and treatment responses around pediatric IBDU. Therefore, it remains challenging to chart the natural history of pediatric IBDU and consequently form an accurate understanding of where pediatric IBDU sits on the spectrum of disease., Competing Interests: The authors declare no conflict of interests.

Distinction between Crohn's disease of the colon-rectum and ulcerative colitis or inflammatory bowel disease (IBD) type unclassified can be of pivotal importance for a tailored clinical management, as each entity often involves specific therapeutic strategies and prognosis. Nonetheless, no gold standard is available and the uncertainty of diagnosis may frequently lead to misclassification or repeated examinations. Hence, we have performed a literature search to address the problem of differential diagnosis in IBD colitis, revised current and emerging diagnostic tools and refined disease classification strategies. Nowadays, the differential diagnosis is an untangled issue, and the proper diagnosis cannot be reached in up to 10% of patients presenting with IBD colitis. This topic is receiving emerging attention, as medical therapies, surgical approaches and leading prognostic outcomes require more and more disease-specific strategies in IBD patients. The optimization of standard diagnostic approaches based on clinical features, biomarkers, radiology, endoscopy and histopathology appears to provide only marginal benefits. Conversely, emerging diagnostic techniques in the field of gastrointestinal endoscopy, molecular pathology, genetics, epigenetics, metabolomics and proteomics have already shown promising results. Novel advanced endoscopic imaging techniques and biomarkers can shed new light for the differential diagnosis of IBD, better reflecting diverse disease behaviors based on specific pathogenic pathways.