Internal and external adenomyosis phenotypes: ultrasound features and association with clinical outcomes

Study question: What are the sonographic and clinical findings in women diagnosed with external and internal adenomyosis by ultrasound?

Summary answer: Patients with external and internal adenomyosis phenotypes, diagnosed by ultrasound, present differences in sonographic features of the disease and demographic characteristics including age, parity, and association with deep endometriosis (DE) and leiomyomas.

What is known already: Two different phenotypes of adenomyosis have been described based on the anatomical location of adenomyotic lesions in the myometrium, suggesting that adenomyosis affecting the inner myometrium and that affecting the external myometrial layer may have distinct origins.

Study design, size, duration: A cross-sectional study including 505 patients with a sonographic diagnosis of adenomyosis was performed between January 2021 and December 2022.

Participants/materials, setting, methods: Women sonographically diagnosed with adenomyosis in a tertiary referral hospital that serves as a national reference center for endometriosis were included over a 2-year period. Patients were divided into two groups (internal and external adenomyosis) according to the myometrial layer affected by adenomyosis. We compared sonographic and clinical outcomes including a multivariate analysis between the two groups.

Main results and the role of chance: According to ultrasound findings, 353 (69.9%) patients presented with internal adenomyosis, while 152 (30.1%) presented with external adenomyosis. Women with internal adenomyosis were significantly older and less frequently nulliparous compared to those with external adenomyosis. Sonographically, internal adenomyosis appeared diffusely, it had a greater number of adenomyosis features, it presented a globular morphology of the uterus more frequently, and it coexisted with leiomyomas more frequently, compared to external adenomyosis. Conversely, the presence of translesional vascularity and associated DE were more common among the external adenomyosis group. No significant differences were found between internal and external adenomyosis groups regarding pain, heavy menstrual bleeding, spotting, or infertility. In the multivariate analysis, nulliparity, the presence of leiomyomas, and the presence of DE were independently associated with adenomyosis phenotypes (the presence of DE and nulliparity increased the risk of external adenomyosis, whereas the presence of leiomyomas was a risk factor for internal adenomyosis). Considering the impact of hormonal treatment, we found that the number of ultrasound adenomyosis criteria was significantly greater in patients without hormonal treatment. Non-treated patients more commonly presented dysmenorrhea or bleeding-associated pain and heavy menstrual bleeding than women on hormonal treatment, although there were no significant differences according to adenomyosis phenotypes.

Limitations, reasons for caution: As the population was selected from the Endometriosis Unit of a tertiary center, there may be patient selection bias, given the high prevalence of individuals with associated endometriosis, previous endometriosis-related surgery, and/or receiving hormonal treatment.

Wider implications of the findings: Transvaginal ultrasound is the most available and cost-effective tool for the diagnosis of adenomyosis. Adenomyosis phenotypes based on ultrasound findings may be key in achieving an accurate diagnosis and in decision-making regarding the most adequate therapeutic strategy for the management of patients with adenomyosis. Determination of the sonographic features associated with symptoms could help in the evaluation of treatment response.

Study funding/competing interest(s): No funding was obtained for this study and there are no conflicts of interest to declare.

Trial registration number: N/A.