Cryptomenorrhea, also known as “hidden menstruation,” occurs when menstrual blood is produced but cannot exit the body due to an obstruction, such as an imperforate hymen or vaginal septum. Here’s a breakdown of the pathophysiology:

1. Menstrual Blood Production: The endometrium (lining of the uterus) sheds its lining during menstruation, producing menstrual blood.
2. Obstruction: A congenital obstruction, such as an imperforate hymen or vaginal septum, blocks the outflow of menstrual blood.
3. Accumulation: The menstrual blood accumulates in the vagina (hematocolpos) or uterus (hematometra), leading to symptoms.
4. Symptoms: Symptoms include cyclic lower abdominal pain, a bulging bluish membrane at the vaginal opening, and sometimes urinary retention.
5. Complications: If untreated, it can lead to complications like endometriosis, infertility, and urinary retention.

Treatment typically involves surgically removing the obstruction to allow menstrual blood to flow normally.