Diagnostic Value of Pelvic and Transperineal Ultrasound in Girls with Central Precocious Puberty

Background: Central precocious puberty (CPP) requires early and accurate diagnosis to prevent adverse physical and psychological consequences. Although the GnRH stimulation test is the diagnostic gold standard, it is invasive, time-consuming, and not readily available in all settings. Pelvic ultrasonography offers a practical non-invasive adjunct, but sonographic criteria vary considerably across populations. Moreover, estrogen-related changes in the vaginal mucosa—despite their diagnostic potential—have been largely overlooked. This study uniquely incorporates transperineal ultrasonography to measure vaginal mucosal and muscular thickness as novel markers for CPP. Methods: In this case–control study conducted from 2021 to 2023, 32 girls with CPP and 32 age-matched controls (all under 8 years) underwent transabdominal pelvic ultrasonography to assess uterine and ovarian dimensions, and transperineal ultrasound to measure vaginal mucosal and wall muscle thickness. Baseline characteristics were compared using Chi-square and Mann–Whitney U tests. ROC curve analysis was performed to determine optimal diagnostic cut-off values. Results: Girls with CPP showed significantly higher uterine length and uterine volume compared with controls. Vaginal mucosal thickness measured via transperineal ultrasound was also significantly increased in the CPP group, highlighting its diagnostic potential. ROC analysis identified uterine length (AUC = 0.747; 26.5 mm) as the strongest discriminator, followed by uterine volume (AUC = 0.734), right ovary width (AUC = 0.724), and right ovary volume (AUC = 0.723). Conclusions: Both transabdominal and transperineal ultrasonography provide valuable non-invasive tools for evaluating girls suspected of CPP. The introduction of vaginal mucosal assessment via transperineal imaging represents a novel diagnostic approach that may improve early identification of CPP, particularly in settings with limited access to GnRH testing. Larger population-based studies are recommended to refine ultrasonographic cut-off values.