KEY FACTS
Terminology
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Synonyms: Peritoneal pseudocyst, benign cystic mesothelioma
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Not true cyst but peritoneal or ovarian fluid trapped by peritoneal adhesions
Imaging
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Unilocular or multilocular pelvic cystic lesion
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Boundaries defined by pelvic structures and walls
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Unilateral in 65%, bilateral in 35%, midline if large
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Normal ovary surrounded or displaced by fluid and septations; entrapped ovary: Spider in web appearance
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Fine septations most common
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Thick septations with nodules possible
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Blood flow can be seen in septations, especially if thick
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Transvaginal ultrasound 1st-line to localize ovary and exclude signs of malignancy
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MR most useful if peritoneal inclusion cyst (PIC) is large and normal ovaries cannot be found using ultrasound
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CT useful for large PIC and for excluding malignant peritoneal disease but less sensitive at locating ovaries
Top Differential Diagnoses
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Ovarian cystic neoplasm
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Hydrosalpinx
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Paraovarian cyst
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Endometriosis
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Lymphangioma/mesenteric cyst
Pathology
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Requires functioning ovary and peritoneal adhesions
Clinical Issues
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Almost exclusively premenopausal women
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Pelvic pain, palpable mass, abdominal distension, or pressure symptoms or incidentally noted on imaging
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Indolent course: May grow, remain stable, or regress
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Tend to recur after drainage
Scanning Tips
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Look for solid components and normal ovary using transabdominal and transvaginal probes
, and consists of simple fluid with thin septa 
.
. A thin adhesion is present 
. The left ovarian follicle 
is smaller; the right ovary has developed a larger cyst 
.
superior and posterior to the uterus 
. Internal echoes were from hemorrhage, confirmed at surgery.
