2 Figure 1: T2-weighted (fat-suppressed) sagittal image of the pelvis reveals a 5.5 cm retrovesical lesion lying anterior to the rectum. It is well circumscribed. There is no pelvic sidewall lymphadenopathy. Figure 2: A cream-coloured ovoid mass is seen anterior to the rectum with the tip of the urethral catheter visible anterior to it. They can mimic acute appendicitis among other causes of acute abdominal pain. In cases of chronic torsion, ischemia ensues leading to saponiﬁcation, calciﬁcation of the fat contents, and atrophy of the pedicle. The appendix epiploica detaches from the colon and becomes a peritoneal loose body or “peritoneal mouse”. It is not uncommon to ﬁnd small loose bodies during laparotomy [4]. Normally, they have little or no pathological signiﬁcance, and their prevalence is not clearly documented. However, giant loose bodies (>5 cms) are very rare, and the process of their development has not yet been fully elucidated [5]. Recent reports have identiﬁed a peritoneal loose body in the presence of a unilateral absence of adnexal structures, thereby postulating childhood adnexal torsion with autoamputation and gradual calciﬁcation [1]. The current case describes a giant peritoneal loose body case masquerading as a pelvis lesion causing signiﬁcant Case Reports in Medicine rectal symptomatology related to extrinsic compression. A pelvic MRI depicted the lesion with features consistent with leiomyoma. There was low signal on the T1- and T2- weighted images with central low signal consistent with central calciﬁcation. It is important to diﬀerentiate leiomy- omas from other lesions such as ﬁbromata, desmoid tumors, teratomas, metastatic lesions of ovarian cancer, calciﬁcation of lymph nodes, and mesenteric cysts [6]. All of these lesions tend to enhance with contrast except peritoneal loose bodies. It was critical to further evaluate the current case with endorectal ultrasonography, palpation, and biopsy to outrule a malignant process in view of the progressive nature of the symptoms. This evaluation resulted in a cranial migration of the lesion such that it remained impalpable and not amenable to ultrasonographic visualisation. Endoscopic examination of the rectum revealed normal rectal mucosa. After the informed consent was obtained, the patient underwent laparoscopic evaluation. This revealed a mobile cream-coloured egg lying anterior to the rectum. This was removed. The rest of the peritoneal contents were normal. Microscopy of the lesion revealed hyalinised ﬁbrocartilagi- nous tissue lined with mesothelial tissue. This lamellar pattern of ﬁbrous tissue with a scarcity of cellular tissue is typical of what is seen histologically in a peritoneal body [7]. 4. Conclusion Giant peritoneal loose bodies are rare clinical entities. Imag- ing is often inconclusive when symptomatic laparoscopic retrieval is recommended to alleviate symptoms and outrule malignancy. Consent Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal. Competing Interests The authors declare that they have no competing interests. Authors’ Contributions Dara O. Kavanagh performed the surgery mentioned in the paper. DC collected the images and made a comprehensive literature review. RF proofread the paper. PC contributed signiﬁcantly to the writing of the paper. All authors read and approved the ﬁnal paper. References [1] K. Koga, H. Hiroi, Y. Osuga, M. Nagai, T. Yano, and Y. Taketani, “Autoamputated adnexa presents as a peritoneal loose body,” Fertility and Sterility, vol. 93, no. 3, pp. 967–968, 2010. [2] T. Mohri, T. Kato, and H. Suzuki, “A giant peritoneal loose body: report of a case,” American Surgeon, vol. 73, no. 9, pp. 895–896, 2007.