The causes of vaginal cysts include vaginal wall injury, duct and structural remains of embryonic development, and fluid accumulation in the gland on the vaginal opening, according to WebMD. The cause of a cyst determines the type of the vaginal cyst.
Vaginal cysts that result from injury to the vaginal wall are called inclusion cysts and are the most common of all the vaginal cysts, says WebMD. Inclusion cysts are typically small-sized and target the vaginal wall's lower back. Episiotomy, is one possible cause of vaginal wall injury.
The duct remnants of embryonic development cause Gartner's duct cysts, reports WebMD. This type of vaginal cyst occurs when a developing embryo's ducts fail to disappear after childbirth, turning into vaginal cysts over time. When a developing baby leaves behind structures, the structures can form a type of vaginal cysts called Mullerian cysts. Typically, Mullerian cysts attack any part of the vaginal wall and are full of mucus.
Fluid buildup in the Bartholin's gland results in Bartholin's gland cysts, notes WebMD. The fluid accumulates due to blockage of the Bartholin's gland opening as a result of bacteria, such as sexually transmitted-disease-causing bacteria including, Neisseria gonorrhoeae, and intestinal tract bacteria, which include E. coli.