Rectosigmoid Endometrioma Mimicking Rectal Hematoma: A Diagnostic Dilemma Managed Conservatively.

Endometriosis is a benign gynecological condition characterized by the presence of functional endometrial tissue outside the uterine cavity. Although it most commonly affects pelvic organs, bowel involvement is uncommon, and rectal endometriosis is particularly rare. Its presentation may mimic colorectal malignancy, inflammatory bowel disease, or rectal hematoma, often resulting in diagnostic delay. We report the case of a 38-year-old multiparous woman who presented with painless hematochezia, cyclical alteration of bowel habits, and lower abdominal cramping pain. Colonoscopy revealed a large intraluminal rectal lesion initially interpreted as a rectal hematoma. Computed tomography (CT) demonstrated a large intramural rectal mass with a concomitant left ovarian cystic lesion. Following multidisciplinary evaluation, a diagnosis of rectal endometrioma was favored. The patient was treated conservatively with gonadotropin-releasing hormone (GnRH) analogue therapy, resulting in the marked radiological regression of both rectal and ovarian lesions. Follow-up colonoscopy confirmed the near-complete resolution of the rectal lesion. The patient declined surgical intervention and remained clinically stable on maintenance hormonal therapy. This case highlights the diagnostic challenge posed by rectal endometriosis and underscores the importance of considering endometriosis in reproductive-aged women presenting with atypical rectal symptoms. Magnetic resonance imaging (MRI) was used to confirm the diagnosis and to monitor treatment response, demonstrating the significant regression of the rectal lesion following hormonal therapy, and selected patients may be successfully managed with medical therapy alone.