Pelvic MRI is the most accurate imaging modality for diagnosing a vaginal septum because it provides high-resolution, multiplanar images that clearly delineate soft tissue structures. This allows precise visualization of the septum’s location, thickness, and length, which is crucial for preoperative planning. Unlike ultrasound or CT, MRI offers superior contrast between different tissues without radiation exposure. Identifying the exact anatomy helps guide surgical excision or reconstruction to restore normal vaginal anatomy and function. Hence, Pelvic MRI is the gold standard for confirming a vaginal septum.

Reference: Clinical Gynecologic Oncology, Philip J. DiSaia, 9th Edition.