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Chocolate cyst

  • this is a blood filled ovarian cyst in which the blood has become thickened and dark. Chocolate cysts are most commonly ovarian endometriotic cysts. They are frequently painful and fixed due to surrounding inflammation.

ovarian endometriotic cysts (endometriomas)

Ovarian endometriomas are ovarian cysts lined by endometriotic tissue. In longstanding disease, fibrotic tissue eventually replaces the endometrial tissue leaving no histological evidence of endometriosis (1).

There are three main theories for the development of endometriomas:

  • the invagination theory
    • most widely expected theory
    • endometrioma begins as endometriosis on the ovarian surface and with adhesions to the adjacent peritoneum, blood and menstrual debris accumulate on the ovarian surface leading to progressive invagination of the ovarian cortex forming a pseudo-cyst
  • the ovarian cyst theory
    • endometriomas begins as a functional ovarian cyst with gradual infiltration of endometriotic tissue
  • metaplasia theory
    • occurs from coelomic metaplasia of invaginated epithelial inclusions on the ovarian surface (1)

Endometriomas can be unilateral or bilateral

  • size may vary from <1 cm to >10 cm in diameter
  • usually contain thick chocolate coloured fluid (which differentiates them from simple haemorrhagic cysts) due to recurrent chronic bleeding
  • the affected ovaries are often adherent to the pelvic side wall, back of the uterus and the broad ligament, but around 10% the ovaries are free from adhesion

Transvaginal ultrasound (TVS) is useful both to make and to exclude the diagnosis of an ovarian endometrioma. In ovarian endometriomas of greater than 3 cm in diameter, histology should be obtained to identify endometriosis and to exclude rare instances of malignancy (2).

Endometriomas do not usually respond to medical therapy (although there can be some temporary clinical relief) (1). Surgery is the treatment of choice.

  • surgical options include laparoscopic excision of the cyst wall or drainage and coagulation of the cyst bed (3).
  • excisional surgery which is associated with less recurrence and more spontaneous pregnancies in subfertile women have been shown to be superior than draining and abalation of the endometrioma (1)
  • a trial comparing immediate laparoscopic ovarian cystectomy with a three step protocol (which involved endometrioma drainage, 3 months of subsequent GnRH agonist therapy and a second laparoscopy for laser coagulation of the cyst wall) have shown that ovarian function is better preserved following the three step surgical procedure than the traditional single step approach (4)


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