Objectives: Adenomyosis is challenging to diagnose with transvaginal ultrasound (TVUS) and requires operator expertise to recognize its sonographic features; however, little is known about the learning curve for trainees. This study aimed to assess the learning curve of inexperienced residents in diagnosing adenomyosis and identifying its key ultrasound signs using the learning curve–cumulative summation test (LC-CUSUM) method. Methods: This prospective cohort study was conducted in 2 tertiary care centers specializing in endometriosis and adenomyosis. Women aged 18–50 undergoing routine outpatient gynecological visits and ultrasound examinations between April 2023 and February 2024 were included. TVUS exams were initially performed by residents without prior formal training in adenomyosis diagnosis. Each scan was subsequently repeated by an expert sonographer, who provided immediate feedback to the trainee. Concordance between residents and experts was assessed for the presence of adenomyosis, its classification, and specific sonographic features. LC-CUSUM analysis was used to construct learning curves and determine when proficiency was achieved. Results: A total of 150 patients were evaluated by 3 residents (50 each), with the sample size predetermined based on prior studies. All residents achieved diagnostic proficiency by the end of their training, requiring 16, 17, and 23 scans, respectively. LC-CUSUM analysis indicated that approximately 20 scans are needed to reach proficiency. While most key features were correctly identified, subendometrial lines/buds and diffuse inner myometrial involvement were more difficult to recognize consistently. Conclusions: Residents without prior experience can achieve proficiency in diagnosing and classifying adenomyosis after approximately 20 TVUS exams, though some features remain more challenging to detect.
