Imaging description

Peritoneal inclusion cysts are collections of ovulatory fluid that are trapped by peritoneal adhesions around the ovary. This pathophysiology leads naturally to the three features that suggest the diagnosis of a peritoneal inclusion cyst:

• The patient is of reproductive age (i.e., ovulating).

• The patient usually has known risk factors for adhesions, such as prior pelvic surgery, endometriosis, or pelvic inflammatory disease.

• A fluid-filled structure that surrounds or abuts an ovary is seen in the pelvis at cross-sectional imaging. The fluid typically conforms to the outline of the pelvic peritoneal cavity (Figure 73.1) [1,2]. Ultrasound may demonstrate a spiderweb pattern of fine internal septations (Figure 73.2) [3].

Importance

The cystic and solid appearance of a peritoneal inclusion cyst in combination with the surrounded ovary may result in consideration of adnexal malignancy, resulting in unnecessary surgery and patient anxiety. Correct identification of a peritoneal inclusion cyst should result in conservative therapy rather than salpingoophorectomy.

Typical clinical scenario

Peritoneal inclusion cysts are typically detected when pelvic imaging is performed in a woman of reproductive age with a history of prior pelvic surgery (Figure 73.3), endometriosis (Figure 73.4), or pelvic inflammatory disease.