Accessory and Cavitated Uterine Malformation (ACUM): Thinking Outside the Box, and Inside the Myometrium, When Working up Chronic Pelvic Pain

INTRODUCTION: Accessory and cavitated uterine malformations (ACUM) are a rare cause of cyclic pelvic pain in young reproductive-aged females. An ACUM is a cavitated cystic lesion within the myometrium that classically presents in the anterolateral uterus inferior to the insertion of the round ligament, which can be excised to relieve the associated pain. Treatment of this curable condition is often delayed as the characteristic lesion is commonly misdiagnosed as either a leiomyoma, adenomyoma, or rudimentary uterine horn. OBJECTIVE: This video aims to diminish misdiagnosis, and expedite treatment of ACUM, by raising awareness regarding this uncommon condition—its definition, clinical presentation, diagnostic workup, and treatment approach. Furthermore, this video aims to distinguish how the presentation of ACUM varies from similar conditions clinically, sonographically, and on MRI, to further enable viewers to expedite appropriate workup and management. METHODS: An educational video on the topic of ACUM, which utilizes a case presentation of a 22-year-old female with 6 years of cyclic pelvic pain worsened with menses, and previously attributed to what was thought to be a uterine leiomyoma. This video clarifies the definition, clinical presentation, imaging findings, diagnostic approach, and treatment of this condition. RESULTS: The video provides a comprehensive overview of ACUM, including critical review of ultrasound and MRI images to enable viewers to appreciate the hallmark characteristics of ACUM compared to those of differential diagnoses. It highlights a straightforward approach to ensure that ACUM is appropriately identified and treated. CONCLUSIONS: This video offers a structured approach to the identification of ACUM, as one of several lesions within the myometrium that may contribute to chronic pelvic pain. By mastering understanding of the clinical and diagnostic features of ACUM, gynecologic surgeons can provide prompt, definitive treatment.