Unicornuate Uterus With a Rudimentary Horn Adenomyoma, Ipsilateral Renal Agenesis, and Deep Infiltrating Endometriosis: A Case Report

Congenital uterine malformations are often difficult to classify, and an incorrect label can carry over for years across successive clinical records. We describe a 39-year-old woman, gravida 1 para 1, referred for chronic pelvic pain and intermenstrual bleeding, whose uterus had previously been recorded as didelphys. Pelvic magnetic resonance imaging, with T2-weighted sequences in three planes, T1-weighted and fat-saturated sequences, diffusion-weighted imaging, and post-gadolinium imaging, instead demonstrated a unicornuate uterus with a left, cavitated, non-communicating functional rudimentary horn (European Society of Human Reproduction and Embryology/European Society for Gynaecological Endoscopy (ESHRE/ESGE) class U4a; American Society for Reproductive Medicine (ASRM) unicornuate uterus with a non-communicating rudimentary horn). The rudimentary horn was almost entirely occupied by a 6 cm adenomyoma, with a small residual endometrial-lined cavity; the contralateral functional horn showed diffuse adenomyosis; a deep infiltrating endometriotic nodule extended to the left pelvic sidewall with neurovascular tethering and rectal tenting but no transmural invasion; the left ovary contained an endometrioma; and the left kidney was absent. Surgery and histopathology confirmed a single cervix with a rudimentary horn fused at the cervical level, together with the adenomyoma, extensive adenomyosis, and ovarian endometriosis; the patient recovered without complications and became asymptomatic. The case shows how imaging settled a long-standing classification error and how a single examination characterized the associated renal and endometriotic findings that follow from the shared embryology of the genital and urinary tracts.