MR findings of ruptured endometrial cyst: comparison with tubo-ovarian abscess

To evaluate the MR findings of ruptured endometrial cyst, focusing on the differentiation from tubo-ovarian abscess (TOA).

We reviewed the records of 21 patients who underwent preoperative MR examinations for TOAs (n=15) or ruptured endometrial cysts (n=6). We evaluated the presence of hyper-intense ascites and hyper-intense peritoneum in T1-weighted sequences, strong enhancement of the peritoneum, hyper-intense content and hyper-intense rim of the ovarian lesion in T1-weighted sequences, and strong wall enhancement of the ovarian lesion. χ2 test was used to assess the relationship between TOA cases versus cases with ruptured endometrial cysts, and the three MR peritoneal findings. We evaluated the relationship between TOA versus non-infected endometrial cysts, and the ovarian MR peritoneal findings, too.

Hyper-intense ascites was found in all of the patients with ruptured endometrial cyst and none with TOA (p<0.0001). Hyper-intense peritoneum was observed in only TOAs cases (4 of 8). Strong peritoneal enhancement was seen in 3 of the 3 patients with ruptured endometrial cyst and 7 of the 13 patients with TOA (p=0.1366). Hyper-intense content of the ovarian lesion was seen more often in the non-infected endometrial cysts than in the TOAs (p=0.001607), while hyper-intense rim was more frequent in TOAs (p=0.000402). Strong wall enhancement was observed only in TOAs (11 of 15) (p=0.001355).

MR images are useful to differentiate ruptured endometrial cyst from TOA.