Adenomyosis and Endometrial Polyps: A Systematic Review of Coexistence Patterns and Diagnostic Contexts

PURPOSE: Adenomyosis (AM) and endometrial polyps (EPs) are frequently identified in women evaluated for abnormal uterine bleeding, pelvic pain, infertility, and peri- or postmenopausal symptoms. However, coexistence estimates arise from heterogeneous clinical and diagnostic pathways. We synthesized bidirectional AM-EP coexistence and examined how source population and ascertainment influenced reported prevalence. PATIENTS AND METHODS: This PROSPERO-registered systematic review (CRD420261304541) followed PRISMA 2020. PubMed, Embase, the Cochrane Library, and Scopus were searched from the earliest date available in each database to July 14, 2026. Studies reporting either direction of AM-EP prevalence were included. Methodological quality was assessed using the Joanna Briggs Institute prevalence checklist. Given clinically heterogeneous populations, denominators, and diagnostic pathways, study-specific estimates were synthesized narratively without pooling. RESULTS: Sixteen observational studies involving 14,917 women were included. EP prevalence among women with AM ranged from 4.3% to 34.6% across 12 studies. AM prevalence among women with EPs ranged from 3.9% to 91.9% across 11 studies and showed substantially greater dispersion. Among seven studies reporting both directions, six yielded higher estimates for AM among women with EPs than for EP among women with AM. In hysteroscopic polypectomy cohorts, AM prevalence was 3.9-14.5%, while hysterectomy-based estimates were more variable and the two highest values, 55.9% and 91.9%, arose from selected surgical or pathology-enriched populations. This asymmetry was consistent with denominator structure, surgical selection, and intensity of myometrial assessment. CONCLUSION: AM and EPs are repeatedly identified together across diverse gynecological pathways, but the observed likelihood of identifying the alternative lesion is strongly pathway-dependent. Identification of one lesion should not end diagnostic consideration when symptoms, imaging findings, infertility, or treatment response remain incompletely explained. Current evidence supports targeted consideration of the alternative lesion, with further evaluation guided by symptoms and clinical pathway, rather than universal dual-pathology screening.