When the appendix hides: the radiologist's guide to appendix variants and mimics

The 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. Similar content being viewed by others Data availability No datasets were generated or analysed during the current study.

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All authors contributed to manuscript revision, critically reviewed the content, and approved the final version of the manuscript. Corresponding authors Ethics declarations Competing interests The authors declare no competing interests. Additional information Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Rights and permissions Springer 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. About this article Cite this article Pavan 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 Received: Accepted: Published: Version of record: DOI: https://doi.org/10.1007/s00261-026-05665-0