CASE 16913 Published on 27.07.2020

Multilocular peritoneal inclusion cyst: a diagnostic challenge


Genital (female) imaging

Case Type

Clinical Cases


Marco Di Serafino1, Filomena Pezzullo1, Francesca Iacobellis1, Valentina Angelini2, Luigi Barbuto1 and Luigia Romano1

1 Department of General and Emergency Radiology, “Antonio Cardarelli” Hospital, Naples, Italy

2 Department of Advanced Biomedical Sciences, "Federico II" University Hospital, Naples, Italy


48 years, female

Area of Interest Emergency, Genital / Reproductive system female, Pelvis, Peritoneum ; Imaging Technique CT, MR
Clinical History

A 48-year-old woman presented with left-sided pelvic pain gradually increasing in intensity over the past 12 hours. She was premenopausal with an anamnestic history of surgical partial cystic ovarian resection. 

Imaging Findings

Contrast-enhanced computed tomography (CECT) of the abdomen and pelvis revealed a low-density, thin-walled, multi-loculated, multi-cystic large pelvic mass of 14 cm in diameter extending into the lower abdomen (Fig. 1) without solid area, calcifications or free fluid, and without lymphadenopathy or peritoneal implants. The mass was not dissociable from the ovaries, suggesting a benign ovarian neoplasm or giant hydrosalpinx. Magnetic resonance imaging (MRI) showed a very large multilocular pelvic cystic mass adhering to the surrounding pelvic structures. The cysts had low signal intensity on T1-weighted images and high signal intensity on T2-weighted images, suggesting serous contents (Fig. 2). Contrast-enhanced T1-weighted images revealed a pseudocystic areas without their own walls and without papillary projections or mural nodules (Fig. 3); involvement of the adnexes was also excluded (Fig. 4). The excision laparoscopy confirmed the presence of a multi-cystic pelvic mass. Histological specimens reported peritoneal inclusion cysts characterized by multiple thin walls, lined by flattened and cuboidal mesothelial cells.


Multilocular peritoneal inclusion cysts (MPICs), also called benign multicystic peritoneal mesothelioma, inflammatory cysts of the peritoneum, postoperative peritoneal cysts, or benign papillary peritoneal cystosis, occur almost exclusively in premenopausal women with a history of abdominal or pelvic surgery, trauma, pelvic inflammatory disease or endometriosis that leads to the development of adhesions within the abdomen and pelvis. These progressively collect the fluid normally produced during ovarian functional phases or inflammatory exudates derived from peritoneal reactivity until a complex pelvic cystic mass develops [1-4]. A common clinical presentation is a progressive lower-abdominal and pelvic pain or a palpable mass [4]. Due to their rarity and non-specific clinical signs, the pre-operative diagnosis of MIPCs is challenging. Although the utility of ultrasound in diagnosing MPICs has been reported, as it can reveal multiple septa and anechoic cystic pelvic collections [5], CECT and MRI may provide more suggestive findings in detection, characterization, and differential diagnosis of MIPCs with the aim of providing an appropriate management work-up.

CECT of an MPIC usually demonstrates a low-density, thin-walled, multi-loculated, multi-cystic mass, providing accurate information about the location and extent of the mass in the pelvis; however, CECT is limited in that it cannot better define the fluid content and the potential involvement of the adnexes [5]. On MRI, an MPIC appears as an irregular mass with low signal intensity on T1-weighted images, and due to its multi-cystic serous content appears bright on the corresponding T2-weighted images, encircling a normal-appearing ovary clearly separate from the cystic locules, without its own walls, internal structure, papillary projection (vegetation) or solid vascularized areas on dynamic phases [5].

Ancillary findings to support the diagnosis also include the lack of metastasis elsewhere, and lymphadenopathy within the abdomen and pelvis as well.

Based on these imaging findings in the absence of adnexal involvement, as much better evidenced on MRI, in a premenopausal female with history of previous pelvic surgery, MIPCs is the most suggestive diagnosis among the options raised in the differential diagnosis.

Differential Diagnosis List
Multilocular peritoneal inclusion cysts
Multilocular peritoneal inclusion cysts
Paraovarian cysts
Ovarian cystadenoma
Final Diagnosis
Multilocular peritoneal inclusion cysts
Case information
ISSN: 1563-4086