Patient's question:
What causes chocolate cysts?Doctor's answer:
(1) Simple ovarian cyst: Follicular cysts or corpus luteum cysts are more common on one side. The cyst wall is thin and distinct, with no adhesions around the cyst. The cyst varies in size and shape with the menstrual cycle. Chocolate cysts of the ovary are more common on both sides. The cyst wall is thicker and less distinct, with extremely low signal shadows on T2WI, surrounded by a low signal ring. They often adhere to surrounding tissues and organs due to repeated bleeding within the cyst, and clinical history of dysmenorrhea is common.(2) Ovarian cystadenoma: Ovarian cystadenomas are more common on one side, with clear cyst wall margins. Clinically, they are often asymptomatic. However, when the cystadenoma ruptures, adhesions may also occur around it. It is necessary to combine clinical history (such as history of dysmenorrhea or acute rupture) for differentiation.
(3) Pelvic abscess: On enhanced scans, the wall of a pelvic abscess shows ring-like enhancement, with a relatively thick enhancement ring. Clinically, there are often signs of inflammation.
(4) Ovarian cancer: When a chocolate cyst of the ovary has fresh bleeding, it may resemble a solid-cystic mass and needs to be differentiated from ovarian cancer. After enhancement, the solid part of ovarian cancer shows significant enhancement or wall nodules, while the hemorrhagic part of chocolate cysts appears solid but shows no enhancement or wall nodules on enhanced scans.
(5) Ovarian cystic teratoma: Cystic teratomas appear as homogeneous high signals on T1WI and T2WI, with chemical shift changes. On fat-suppression sequences, they show low signals, which is the best method for differentiation. Cystic teratomas often contain calcifications and generally do not adhere to surrounding tissues.