WCN26-2390 Tunnel Infections due to Multidrug-Resistant Mycobacterium abscessus Requiring Catheter Removal in a Peritoneal Dialysis Patient

Introduction: Morphological alterations of mesothelial cells are importantly associated with the pathogenesis of peritoneal dialysis (PD)-related peritoneal sclerosis and encapsulating peritoneal sclerosis.However, observation of mesothelial cells is often difficult with light microscopy (LM), whereas transmission electron microscopy lacks simplicity and comprehensiveness for routine assessment.Low-vacuum scanning electron microscopy (LVSEM) is a modified technique applicable to paraffin-embedded sections, allowing detailed morphological evaluation of tissue architecture with simple preparation.Although LVSEM has been applied to kidney pathology, it has never been used to evaluate the peritoneum.We applied LVSEM to peritoneal biopsy specimens from several pediatric PD patients to explore its feasibility, practicality, and potential advantages in peritoneal assessment.Methods: Peritoneal biopsy specimens from seven pediatric patients at PD initiation and four patients at PD catheter removal, including three evaluated at both time points, were examined using LVSEM.Sections were stained with periodic acid-methenamine (PAM) and elastica-Masson trichrome staining for both LM and LVSEM, and with platinum-blue for LVSEM, as heavy-metal staining required for LVSEM visualization.Platinum-blue was used to visualize cellular morphology, including mesothelial cells, whereas PAM was mainly used to highlight microvilli.Elastica-Masson trichrome was used for the evaluation of interstitial fibrous components.Morphological findings were compared between LM and LVSEM.Results: The median age at PD initiation among the seven patients was 13 years (range, 3-16).The median PD duration among the four patients evaluated at PD catheter removal was 21.7 months (range, 1.5-56.5).At PD initiation, mesothelial cell detachment was absent in all seven cases, and microvilli were clearly observed.At PD catheter removal, mesothelial cell detachment was observed in 81.5% (range, 53.3-100%) of the peritoneum, and microvilli were sparse and shortened.In patients who had undergone PD for more than one year, mesothelial cell detachment involved over 70% of the examined area.In the patient who underwent PD for 1.5 months, mesothelial cells appeared hypertrophic.Conclusion: This study demonstrates the feasibility of applying LVSEM to peritoneal specimens for the first time, allowing simple and detailed observation of mesothelial cells.Further investigations involving more cases are warranted to validate these findings and establish LVSEM as a novel tool in peritoneal pathology.I have no potential conflict of interest to disclose.I used generative AI and AI-assisted technologies in the writing process.During the preparation of this work, the authors used ChatGPT (OpenAI, San Francisco, CA, USA) in order to improve the English language and readability of this abstract.After using this service,