To evaluate presence and characteristics of endometriosis/adenomyosis in premenopausal women with inflammatory bowel diseases (IBD) and to compare symptoms, endometriosis /adenomyosis type and distribution between patients with and without IBD.

This retrospective observational study included premenopausal women with IBD who underwent transvaginal ultrasound at the Gynaecological Ultrasound Unit, University of Rome “Tor Vergata” between January 2021 and January 2025. Women with IBD and ultrasound-confirmed endometriosis/adenomyosis (Study Group) were compared with two control groups: (A) IBD patients without endometriosis/adenomyosis, and (B) women with endometriosis/adenomyosis but without IBD, matched 1:3 for age and BMI.

Among 111 IBD patients, endometriosis/adenomyosis was diagnosed in 65 (58.6%). Dysmenorrhea (90.8% vs 65.2%, p = 0.0009), dyspareunia (63.1% vs 32.6%, p = 0.001), and heavy menstrual bleeding (61.5% vs 37.0%, p = 0.01) were significantly more frequent in the Study Group than in Group A. Compared with the Group B, patients in the Study Group reported more bowel symptoms (32.3% vs 15.9%, p = 0.004), especially diarrhoea, and had a higher prevalence of adenomyosis (75.4% vs 61.5%, p = 0.04) and left uterosacral ligament involvement (66.2% vs 51.3% p = 0.03), whereas ovarian endometriosis and posterior deep infiltrating lesions were more common in Group B.

IBD should be suspected in women with endometriosis, particularly those with bowel symptoms and diarrhoea. Whereas endometriosis is highly present in IBD women with typical

gynaecological pain symptoms. The frequent coexistence of adenomyosis and site-specific pelvic involvement suggests shared inflammatory pathways. Multidisciplinary evaluation is crucial to reduce diagnostic delay and improve reproductive health outcomes in this population.