The Pivotal role of hysteroscopy in diagnosing subtle uterine lesions in infertile patients: Seeing the unseen can make the difference

•Subtle uterine lesions can impair fertility without major anatomical changes.•These lesions include T-shaped uterus, cystic lesions, adenomyosis and cervicitis.•Other lesions include cervical and tubal endometriosis, chronic endometritis, thin endometrium, and calcifications.•Identifying these lesions via hysteroscopy is challenging and lacks clear guidelines.•Accurate detection and treatment are crucial to improve reproductive outcomes. Subtle uterine lesions are abnormal intracavitary conditions that, while not causing significant anatomical changes, can adversely impact fertility. Identifying these “subtle” lesions is challenging due to arbitrary interpretation, varied management strategies, unclear clinical significance, and insufficient clinician training in recognizing them. Hysteroscopy offers direct visualization and the capacity to obtain targeted biopsies, making it an invaluable tool for the diagnosis and treatment of these often overlooked conditions. The lack of standardized and universally accepted terminology complicates the diagnosis and treatment of subtle uterine pathologies. A thorough understanding of how to identify and effectively manage these lesions is essential for the treatment of infertile patients. This review summarizes the critical and evolving subtle uterine lesions that clinicians frequently overlook during hysteroscopic procedures, highlighting the importance of accurate identification and its potential to improve reproductive outcomes. This literature review followed the Scale for the Quality Assessment of Narrative Review Articles (SANRA) guidelines. All articles discussing infertility-related issues and subtle lesions diagnosable with hysteroscopy were deemed eligible for inclusion. We identified several subtle uterine lesions that are often overlooked during routine hysteroscopic evaluations but can adversely impact fertility. These include morphological abnormalities such as the T-shaped uterus, cystic lesions of the uterine wall, adenomyosis, cervicitis, cervical and tubal endometriosis, and endometrial conditions such as chronic endometritis, thin endometrium and endometrial calcifications. Effective diagnosis and treatment of subtle uterine lesions is essential to fertility care. Knowing which lesions are commonly missed and understanding their endoscopic features and potential clinical implications, is crucial for enhancing the diagnostic capacity of hysteroscopy. This, in turn, may improve reproductive outcomes a