An ovarian cyst is a fluid-filled sac within the ovary. They usually cause no symptoms, but occasionally they may produce bloating, lower abdominal pain, or lower back pain. The majority of cysts are harmless. If the cyst either breaks open or causes twisting of the ovary, it may cause severe pain. Wikipedia
Symptoms: None, bloating, lower abdominal pain, lower back pain
Treatment: Conservative management, pain medication, surgery
Complications: Rupture, twisting of the ovary
Frequency: 8% symptomatic before menopause
Prevention: Hormonal birth control
Prognosis: Usually good