Ruptured Endometrial Cysts as a Rare Cause of Acute Pelvic Pain: Can We Differentiate Them From Ruptured Corpus Luteal Cysts on CT Scan?

Purpose: To evaluate the usefulness of CT in the differentiation of ruptured endometrial cysts and corpus luteal cysts. Methods: Sixteen patients (mean age, 26 years) with a surgically proven ruptured endometrial cyst and 19 patients (mean age, 28 years) with a surgically proven corpus luteal cyst were included in this study. All patients had undergone portal phase contrast-enhanced computed tomographic (CT) scans. We retrospectively analyzed the CT findings on the ovarian cysts for the size and shape of the ovarian cyst, the thickness of the cyst wall, the attenuation of the cyst content, the presence of a discontinuity of the cyst wall, and on the peritoneum for the amount and attenuation of the ascites and the presence of hazy infiltration in the peritoneal fat. We compared the CT imaging characteristics in patients with ruptured endometrial cysts and corpus luteal cysts, using the Mann-Whitney U test. Results: Ruptured endometrial cysts tend to show larger, multilocular cysts with a thicker wall compared to ruptured corpus luteal cysts (P < 0.05). A distorted shape of the cyst was more commonly seen in ruptured endometrial cyst, but direct CT findings that can suggest a rupture of an ovarian cyst, such as a discontinuity of the cyst wall and hemoperitoneum, were more commonly seen in ruptured corpus luteal cysts than in endometrial cysts (P < 0.05). Conclusions: Computed tomography is useful in the differentiation of ruptured endometrial cysts and corpus luteal cysts in a patient with acute pelvic pain.