An ovarian follicle that is larger than 2 centimeters is an ovarian cyst, an accumulation of fluid within an ovary surrounded by a very thin wall, explains Medical News Today. Ovarian cysts range greatly in size; some are as small as a pea, and others are larger than an orange.
A functional cyst that forms during ovulation is the most common type of cyst, according to WebMD. It occurs when either the egg is not released, or the follicle in which the egg forms does not dissolve after the egg is released. Sometimes the follicles in which the eggs normally mature fail to open and form cysts. This condition is called polycystic ovary syndrome. Endometriosis can cause tissue from the lining of the uterus to grown in the ovaries, causing pain and affecting fertility. Fluid-filled cystadenomas form out of cells on the surface of the ovary, and dermoid cysts contain tissue similar to that found in hair, skin and teeth.
Symptoms of ovarian cysts include painful menstruation and abnormal bleeding; difficulty urinating, or a frequent need to urinate; a dull ache in the lower back; and pain or bloating in the abdomen, states WebMD. Cysts are often diagnosed during routine pelvic exams. They are confirmed by imaging tests such as ultrasound, MRI or CT. Blood tests to determine hormone levels and look for CA-125 are also used to diagnose cysts, as well as laparoscopy.