Hematocolpos is a medical condition in which the vagina

Vagina

The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

 fills with menstrual blood. It is often caused by the combination of menstruation with an imperforate hymen.

A related disorder is hematometra

Hematometra

Hematometra is a medical condition involving collection of blood in the uterus. It can rarely be caused by a proximal transverse vaginal septum, as can hematosalpinx.A collection or retention of blood in the uterine cavity. Also called hemometra....

, where the uterus fills with (menstrual) blood. This can be caused by a congenital stenosis

Stenosis

A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure.It is also sometimes called a stricture ....

 of the cervix

Cervix

The cervix is the lower, narrow portion of the uterus where it joins with the top end of the vagina. It is cylindrical or conical in shape and protrudes through the upper anterior vaginal wall...

, or by a complication of a surgical treatment, with stenosis of the cervix.