A 13-year old girl came to the casualty with acute lower abdominal pain. She had a cyclical pain for the last 6 months. She has not yet attained her menarche. On examination, a tense bulge was seen in the region of the hymen. The most probable diagnosis is?

Imperforate hymen: congenital disorder where a hymen without an opening completely obstructs the vaginal outflow. Prevents the drainage of menstrual blood. This results in the accumulation of blood in the vagina leading to hematocolpos. This is visualised as the tense bulge. In long standing cases it can even lead to hematometra. Treatment involves a cruciate incision on the hymen with drainage of hematocolpos/ hematometra