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IntroductionAppendicitis is one of the most common causes of acute abdominal surgery in children. The clinical course of appendicitis ranges from simple to complex appendicitis. The mechanisms underlying the heterogeneity of appendicitis in children remain largely unclear. Dysregulated T cell responses play an important role in several inflammatory diseases of the intestine, but the extend of T cell dysregulation in appendicitis in children is less well known.MethodsTo characterize appendiceal T cells in simple and complex appendicitis we performed in-depth immunophenotyping of appendiceal-derived T cells by flow cytometry and correlated this to appendiceal-derived microbiota analyses of the same patient.ResultsAppendix samples of twenty children with appendicitis (n = 8 simple, n = 12 complex) were collected. T cells in complex appendicitis displayed an increased differentiated phenotype compared to simple appendicitis, including a loss of both CD27 and CD28 by CD4+ T cells and to a lesser extent by CD8+ T cells. Frequencies of phenotypic tissue-resident memory CD69+CD4+ T cells and CD69+CD8+ T cells were decreased in children with complex compared to simple appendicitis, indicating disruption of local tissue-resident immune responses. In line with the increased differentiated phenotype, cytokine production of in particular IL-17A by CD4+ T cells was increased in children with complex compared to simple appendicitis. Furthermore, frequencies of IL-17A+ CD4+ T cells correlated with a dysregulation of the appendiceal microbiota in children with complex appendicitis.ConclusionIn conclusion, disruption of local T cell responses, and enhanced pro-inflammatory Th17 responses correlating to changes in the appendiceal microbiota were observed in children with complex compared to simple appendicitis. Further studies are needed to decipher the role of a dysregulated network of microbiota and Th17 cells in the development of complex appendicitis in children.

Abstract Background and Aims Although appendicitis is rare in young infants, the reported mortality is high. Primary aim of this systematic review was to provide updated insights in the mortality and morbidity (postoperative complications, Clavien‐Dindo grades I–IV) of appendicitis in infants ≤3 months of age. Secondary aims comprised the evaluation of patient characteristics, diagnostic work‐up, treatment strategies, comorbidity, and factors associated with poor outcome. Methods This systematic review was reported according to the PRISMA statement with a search performed in Pubmed, Embase and Web of Science (up to September 5th 2022). Original articles (published in English ≥1980) reporting on infants ≤3 months of age with appendicitis were included. Both patients with abdominal appendicitis and herniated appendicitis (such as Amyand's hernia) were considered. Data were provided descriptively. Results In total, 131 articles were included encompassing 242 cases after identification of 4294 records. Overall, 184 (76%) of the 242 patients had abdominal and 58 (24%) had herniated appendicitis. Two‐hundred (83%) of the patients were newborns (≤28 days) and 42 (17%) were infants between 29 days and ≤3 months of age. Either immediate, or after initial conservative treatment, 236 (98%) patients underwent surgical treatment. Some 168 (69%) patients had perforated appendicitis. Mortality was reported in 20 (8%) patients and morbidity in an additional 18 (8%). All fatal cases had abdominal appendicitis and fatal outcome was relatively more often reported in newborns, term patients, patients with relevant comorbidity, nonperforated appendicitis and those presented from home. Conclusion Mortality was reported in 20 (8%) infants ≤3 months of age and additional morbidity in 18 (8%). All patients with fatal outcome had abdominal appendicitis. Several patient characteristics were relatively more often reported in infants with poor outcome and adequate monitoring, early recognition and prompt treatment may favour the outcome.

The aim of this study was to evaluate the annual, seasonal and monthly trends in children with simple and complex appendicitis and their correlation to common viral pathogens in the Netherlands. A consecutive multicenter retrospective cohort study was performed between 2010 and 2019 including children (p < 0.001). An overall decline was demonstrated for both simple and complex appendicitis between 2010 and 2019. No seasonal variation was found for simple appendicitis. For complex appendicitis, the highest number of patients was found in spring, and lowest in summer (N = 372, spring 28.2 ± 5.1% versus summer 21.0 ± 5.8%, p = 0.011), but the variance was regarded as not relevant (p = 0.026) and simple appendicitis with Adenovirus NON 40.41 (R = 0.332, 95%CI 0.019–0.586, p = 0.039), but these correlations did not remain significant after a Bonferroni correction (p < 0.003). In conclusion, we found no relevant seasonal variation for simple or complex appendicitis, nor positive correlation with common viral pathogens.

IntroductionRecent studies have shown that specific cases of post-appendectomy abscess (PAA) in children could be treated conservatively. However, due to the lack of high-quality evidence, choice of treatment still depends on preferences of the treating surgeon, leading to heterogeneity in clinical practice. Therefore, we aimed to provide an update of recent literature on the management of PAA in children and subsequently evaluate the outcomes of a large multicenter cohort of children treated for PAA.MethodsA literature search was performed in Pubmed and Embase, selecting all randomized controlled trials, prospective and retrospective cohort studies, and case series published from 2014 and onward and reporting on children (