Cervicovaginal adhesions causing obstructive hematocolpos and endometrial thickening after pelvic radiotherapy for rectal cancer: a case report with 12-month follow-up

Abstract Background Cervicovaginal adhesion with obstructive hematocolpos is an uncommon late complication after pelvic radiotherapy for rectal cancer. In young women with severely diminished ovarian reserve, apparent endometrial thickening on ultrasound is traditionally attributed to estrogen, but this explanation is less convincing in the setting of profound estrogen suppression. In this case, the 19 mm measurement likely reflected retained intracavitary blood (pseudothickening) rather than true proliferative endometrium, as histopathology confirmed only coagulated blood and necrotic debris. Case presentation A 36-year-old woman, treated with pelvic radiotherapy and gonadotropin-releasing hormone agonist for rectal cancer in 2024, presented in July 2025 with acute lower abdominal pain. Gynecological examination revealed dense adhesions approximately 2 cm above the hymen, with the cervix not visible. Transvaginal ultrasound showed a 72 × 42 × 50 mm mixed-echo mass and apparent endometrial thickening of 19 mm. The 19-mm measurement likely reflected retained blood and clots within the obstructed cavity rather than true endometrial proliferation. Serum estradiol was < 15 pg/mL and follicle-stimulating hormone was 13.32 IU/L. Multidisciplinary surgical exploration included adhesiolysis, evacuation of retained blood, cervical canal recanalization, hysteroscopy, and curettage. Postoperative immunohistochemistry (PAX-8-positive, CK7-positive; CK20-negative, CDX2-negative) was consistent with endometrial origin; definitive exclusion of metastasis was limited by fragmented specimen. A silicone vaginal mold was placed postoperatively as an individualized measure, with gradual tapering over 10 months. Menstruation resumed one month after surgery, with resolution of dysmenorrhea. Endometrial thickness decreased to 5 mm within 1.5 months and stabilized at 4 mm at 11 months. At 12-month follow-up, estradiol had risen to 44.67 pg/mL, but anti-Müllerian hormone was only 0.17 ng/mL, indicating severely diminished ovarian reserve despite partial endocrine recovery. Conclusions Apparent endometrial thickening in radiotherapy survivors may reflect retained intracavitary blood (pseudothickening) rather than true endometrial proliferation. Cervicovaginal obstruction should be considered in young female cancer survivors with pelvic pain or abnormal bleeding. Individualized vaginal mold therapy may help maintain genital tract patency, but optimal duration and patient selection require further study.