Characteristic Appearance of Ruptured Endometriotic Cyst Fluid
When an endometriotic cyst ruptures in the abdomen, the fluid is characteristically described as "chocolate brown" or "dark chocolate colored" due to degenerated blood products from hemorrhage of ectopic endometrial tissue. 1, 2, 3
Fluid Characteristics
The fluid released from a ruptured endometrioma has several distinctive features:
- Color: Dark chocolate brown or chocolate-colored fluid is the hallmark appearance 1, 3
- Composition: The fluid consists of degenerated blood products from repeated hemorrhage of ectopic endometrial tissue 2
- Associated findings: The fluid may be accompanied by hemorrhagic (bloody) pelvic free fluid when visualized on imaging 4
Clinical Presentation and Imaging Findings
When endometriotic cysts rupture, they present with specific clinical and radiological features:
- Imaging appearance: CT or ultrasound may demonstrate an irregular peripherally enhancing adnexal cyst accompanied by hemorrhagic pelvic free fluid 4
- Free fluid characteristics: Echoes within the free intraperitoneal fluid are often due to blood, and more than a trace amount of free fluid or echoes within the fluid raises concern for rupture 4
- Clinical severity: Ruptured endometriomas can cause acute peritonitis, hemoperitoneum, and present with severe generalized abdominal pain 5, 2
Important Clinical Pitfalls
Several critical considerations when evaluating suspected ruptured endometriomas:
- Mimics malignancy: The combination of complex cystic masses, hemorrhagic ascites, and peritoneal deposits can mimic ovarian malignancy with carcinomatosis 2
- Falsely elevated tumor markers: Cancer antigen-125 (CA-125) and CA 19-9 can be falsely elevated in the setting of ruptured endometrioma, potentially leading to misdiagnosis of malignancy 2
- Rare but serious complication: Rupture occurs in less than 3% of women with endometriosis but can lead to sepsis, septic shock, and can be lethal if infected 5
- Infection risk: Although rare, endometriotic cysts can become infected and rupture, causing acute diffuse peritonitis with purulent fluid mixed with the characteristic chocolate-colored content 5, 6