{"paper_id":"b319ac72-76c0-4054-b72d-1478727360a8","body_text":"Abstract\nPurpose\nTo evaluate intraobserver and interobserver agreement in the interpretation of subtle MRI findings classified as minimal endometriosis, to assess the impact of the Kappa paradox in low-prevalence compartments, and to compare blinded rereads with the original prospective reports.\nMaterials and methods\nIn this retrospective study, 100 pelvic MRI examinations (50 originally reported as minimal or incipient endometriosis and 50 originally reported as normal) were independently reviewed by three radiologists on two blinded occasions 4–8 weeks apart. Seven anatomical compartments were assessed. Agreement was measured with Cohen’s Kappa, Fleiss’ Kappa, PABAK, Gwet’s AC1, and positive/negative agreement. Original reports were used as a clinical reference for descriptive comparison, and exact McNemar tests assessed directional asymmetry of discordance.\nResults\nIntraobserver agreement for any finding was fair (mean Kappa = 0.36, 95%CI 0.16–0.54; AC1 = 0.49), and interobserver agreement was also fair (Fleiss Kappa = 0.28; AC1 = 0.40). Agreement was consistently stronger for negative than for positive classifications. Ovarian findings showed the highest reproducibility, whereas very low-prevalence compartments showed a marked Kappa paradox. Multicategory analysis of uterosacral ligament laterality reduced agreement, mainly because unilateral-versus-bilateral disagreement remained frequent among positive cases. Comparison with original reports showed slight-to-moderate agreement (Kappa 0.18–0.46), with specificity (76–86%) consistently exceeding sensitivity (32–66%), indicating a more restricted threshold on blinded rereads, particularly for uterosacral ligament involvement.\nConclusions\nAgreement for subtle MRI findings interpreted as minimal endometriosis was only fair and clearly lower than that usually reported for deep endometriosis. Low-prevalence compartments were strongly affected by the Kappa paradox, and the low-to-moderate discordance with original reports, driven primarily by lower sensitivity on blinded rereads, supports the need for clearer operational criteria and more standardized interpretation.\nSimilar content being viewed by others\nData availability\nThe datasets generated and analysed during the current study are available from the corresponding author on reasonable request.\nReferences\nGiudice LC, Kao LC (2004) Endometriosis. 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Acta Obstet Gynecol Scand 100:1165–1175. https://doi.org/10.1111/aogs.14099\nAcknowledgements\nThe authors thank Lucas Damiani and Renato Hideo Nakagawa Santos (Instituto de Pesquisa, Hospital do Coração - HCor, São Paulo, Brazil) for their assistance with the methodology and statistical analysis.\nAuthor information\nAuthors and Affiliations\nContributions\nH.L.F. conceived and designed the study, collected data, performed the image analysis, conducted the statistical analysis, and drafted the manuscript. M.F.A. and M.S.C. independently performed the blinded image analyses used for intra- and interobserver agreement assessment and contributed to data collection. A.S. provided institutional resources and supervision. H.L.F. revised the final version. All authors reviewed and approved the submitted manuscript and agree to be accountable for the accuracy and integrity of the work.\nCorresponding author\nEthics declarations\nConflict of interest\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.\nSupplementary Information\nBelow is the link to the electronic supplementary material.\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\nLeao Filho, H., Figueiredo Alves, M., Sousa de Castro, M. et al. Reproducibility of subtle MRI findings suggestive of minimal endometriosis: agreement, Kappa paradox, and interpretive variability. Abdom Radiol (2026). https://doi.org/10.1007/s00261-026-05661-4\nReceived:\nAccepted:\nPublished:\nVersion of record:\nDOI: https://doi.org/10.1007/s00261-026-05661-4","source_license":"public-domain-us","license_restricted":false}