{"paper_id":"2df2ce1b-64a2-4b66-922d-6604a7bdf515","body_text":"Abstract\nThe identification of the appendix often presents a diagnostic challenge due to its significant anatomical variability, compounded by the frequency with which appendiceal pathologies manifest as atypical clinical presentations that mimic diverse abdominal and pelvic conditions. Beyond acute appendicitis, a wide spectrum of inflammatory, infiltrative, and neoplastic processes can involve the appendix, necessitating the rigorous recognition of their distinct imaging signatures. This pictorial essay reviews the normal anatomy of the appendix, its positional variations, and the spectrum of diseases that may affect it, including acute appendicitis, endometriosis, epiploic appendagitis, appendiceal diverticulitis, mucocele, and primary tumors. While computed tomography (CT) remains the gold standard for primary diagnostic evaluation, magnetic resonance imaging (MRI) serves as a critical complementary modality in specific clinical scenarios, providing superior soft-tissue characterization and improving diagnostic confidence in challenging cases. Recognition of anatomical variants and the primary mimics of the appendix is essential for the accurate interpretation of abdominal imaging studies.\nSimilar content being viewed by others\nData availability\nNo datasets were generated or analysed during the current study.\nReferences\nWhitley S, Sookur P, McLean A, Power N. The Appendix on CT. Clin. Radiol. 2009. p. 190–9. https://doi.org/10.1016/j.crad.2008.06.015\nConstantin M, Petrescu L, Mătanie C, Vrancianu CO, Niculescu AG, Andronic O, et al. The Vermiform Appendix and Its Pathologies. Cancers (Basel). Multidisciplinary Digital Publishing Institute (MDPI); 2023. https://doi.org/10.3390/cancers15153872\nWakeley CPG. 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Rev bras Coloproct. 2011. https://doi.org/10.1590/S2237-93632011000300008\nMohamed A, Wu S, Hamid M, Mahipal A, Cjakrabarti S, Bajor D, et al. Management of Appendix Neuroendocrine Neoplasms: Insights on the Current Guidelines. Cancers (Basel). MDPI; 2023. https://doi.org/10.3390/cancers15010295\nAuthor information\nAuthors and Affiliations\nContributions\nA.H.P.A. and D.L.M. conceived and designed the study. A.H.P.A., C.B.N.B., and M.C.M. performed the literature review and article selection. M.A.M.R., D.L.M., E.A.F.M., and G.B.N. selected the clinical cases and imaging studies. A.H.P.A. drafted the initial manuscript. D.L.M. supervised and guided the project. All authors contributed to manuscript revision, critically reviewed the content, and approved the final version of the manuscript.\nCorresponding authors\nEthics declarations\nCompeting interests\nThe authors declare no competing interests.\nAdditional information\nPublisher’s Note\nSpringer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.\nRights and permissions\nSpringer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.\nAbout this article\nCite this article\nPavan Amaral, A., Bonetto Nicolau Bignotto, C., Alves Ferreira Martins, E. et al. When the appendix hides: the radiologist’s guide to appendix variants and mimics. Abdom Radiol (2026). https://doi.org/10.1007/s00261-026-05665-0\nReceived:\nAccepted:\nPublished:\nVersion of record:\nDOI: https://doi.org/10.1007/s00261-026-05665-0","source_license":"public-domain-us","license_restricted":false}