Abstract
BACKGROUND: Hematocolpos due to imperforate hymen is an important differential diagnosis of abdominal pain in early adolescent stage. However, hematocolpos due to lower vaginal agenesis must be considered because the management differs. CASE PRESENTATION: A healthy 11-year-old girl presented with a 2-day left lower abdominal pain history. Her breast development had begun, but she had not reached menarche. Computed tomography showed high absorptive value liquid filling the upper vaginal to uterine cavity, a pale highly absorptive fluid component suggestive of hemorrhagic ascites in the abdominal cavity on both sides of the uterus, and normal bilateral ovaries. Magnetic resonance imaging diagnosed hematocolpos due to lower vaginal agenesis. The blood clot was aspirated with a transabdominal ultrasound-guided transvaginal puncture. CONCLUSION: History-taking, imaging tests, and appropriate collaboration with obstetrician/gynecologist with awareness of secondary sexual characteristics were crucial in this case.