A small fluid-filled sac near the opening of the vagina.

A Bartholin's cyst likely is caused by a backup of fluid. Glands on each side of the vaginal opening release fluid that helps lubricate the vagina. The openings of these glands can become blocked, causing fluid to back up into the gland.

A Bartholin's cyst can cause a lump or mass to form near the opening of the vagina. Most often, the cyst is painless. If the cyst becomes infected, the infection may cause tenderness, pain or a fever.

Treatment for a Bartholin's cyst depends on the size of the cyst, how painful it is and whether it is infected. Treatment options can include sitz baths, surgery to drain the cyst and medicines to clear up an infection.