A Rare Case of Descending Colon Endometriosis

Endometriosis is the presence of functional endometrial glands and stroma outside the uterine cavity, most commonly affecting the ovaries, uterosacral ligaments, and rectosigmoid colon. Descending colon involvement is exceptionally rare, likely due to coelomic metaplasia. We present a 40-year-old woman with cyclical left flank pain and menorrhagia. MRI revealed adenomyosis and a T1 hyperintense lesion along the descending colon wall, further characterized on CT as a heterogeneously enhancing serosal lesion. Surgical excision confirmed endometriotic involvement. This case highlights the importance of considering bowel endometriosis in reproductive-age women with cyclical abdominal pain and atypical bowel lesions.