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To investigate the clinical manifestations, pathological features, and ultrasonographic characteristics of accessory cavitated uterine malformation (ACUM), and to improve the accuracy of its ultrasonographic diagnosis.

Three patients (patient 1, 2, 3) with ACUM who presented to the Guangzhou Women and Children′s Medical Center, Guangzhou Medical University, from 2015 to 2025 were enrolled. All patients were diagnosed with ACUM by ultrasonography (including transabdominal, transvaginal, and transrectal ultrasound; hereafter collectively referred to as ultrasonography) and subsequently confirmed by histopathological examination of surgically resected specimens. Their clinical manifestations, pathological findings, ultrasonographic features, treatment, and therapeutic outcomes were retrospectively analyzed. In addition, a literature review of studies related to ACUM published in Chinese and international databases from January 1, 2010 to March 1, 2025 was conducted to summarize the clinical characteristics of ACUM and the key points for ultrasonographic diagnosis.

① All 3 patients diagnosed with ACUM in our center sought medical attention because of severe dysmenorrhea refractory to medical treatment. Patient 1 also had endometrial polyps and endometriosis, and patient 3 had right ovarian cyst. Transvaginal or transrectal ultrasound revealed a mass adjacent to the uterus near the uterine horn, containing a cystic anechoic area with poor sound transmission; fine punctate echoes were visible within the anechoic area. Color Doppler flow imaging (CDFI) results showed strip-like blood flow signals around the mass. Histopathological examination results of the resected specimens of 3 patients showed that the lesions were located within the myometrium; the inner wall was lined by endometrial glands and interstitium, and the outer layer was surrounded by smooth muscle, forming a uterus-like structure. All 3 patients underwent laparoscopic excision of the accessory cavitated mass. Dysmenorrhea completely resolved in patient 2 and 3, whereas patient 1 continued to have obvious left lower abdominal pain, which was aggravated during menstruation. ② Literature review results: a total of 64 studies on ACUM were included, involving 176 ACUM patients. Comprehensive analysis of the clinical data of 179 patients with ACUM, including the 3 patients in the present study, showed that the patients ranged in age from 14 to 47 years, with a mean age of 24.6 years. The most common chief complaint was dysmenorrhea (82.4%, 108/131), followed by chronic pelvic or abdominal pain (36.4%, 47/129), and 3 patients reported infertility. ACUM located on the left side of the uterus accounted for 55.9% and on the right side accounted for 43.6%, and 1 case located on the posterior uterine wall. The diameter of all accessory cavities was ≤10 cm. Treatment methods of ACUM included laparoscopic mass excision (85.6%), laparoscopic hysterectomy (2.5%), open mass excision (7.6%), ethanol sclerotherapy (4.2%), and open hysterectomy (0.8%). Among patients who completed follow-up, 87.5% experienced complete resolution of clinical symptoms after surgery.

For young women with progressively worsening dysmenorrhea and pelvic pain that are refractory to medical treatment, ACUM should be considered if an isolated thick-walled cystic-solid structure with a regular shape is found in the myometrium by ultrasonography.