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HOME > J Pathol Transl Med > Volume 47(4); 2013 > Article
Case Study
A Giant Peritoneal Loose Body
Hyun-Soo Kim, Ji-Youn Sung1, Won Seo Park2, Youn Wha Kim1
Korean Journal of Pathology 2013;47(4):378-382.
DOI: https://doi.org/10.4132/KoreanJPathol.2013.47.4.378
Published online: August 26, 2013
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  • 17 Scopus

Department of Experimental Analysis, Aerospace Medical Center, Republic of Korea Air Force, Cheongju, Korea.

1Department of Pathology, Kyung Hee University School of Medicine, Seoul, Korea.

2Department of Surgery, Kyung Hee University School of Medicine, Seoul, Korea.

Corresponding Author: Youn Wha Kim, M.D. Department of Pathology, Kyung Hee University School of Medicine, 26 Kyunghee-daero, Dongdaemun-gu, Seoul 130-701, Korea. Tel: +82-2-958-8743, Fax: +82-2-958-8730, kimyw@khu.ac.kr
• Received: July 13, 2012   • Revised: September 25, 2012   • Accepted: October 8, 2012

© 2013 The Korean Society of Pathologists/The Korean Society for Cytopathology

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

  • Peritoneal loose bodies (PLBs) are usually discovered incidentally during laparotomy or autopsy. A few cases of giant PLBs presenting with various symptoms have been reported in the literature. Here, we describe a case of a giant PLB incidentally found in the pelvic cavity of a 50-year-old man. Computed tomography revealed a free ovoid mass in the pelvic cavity that consisted of central dense, heterogeneous calcifications and peripheral soft tissue. The mass was an egg-shaped, hard, glistening concretion measuring 7.5×7.0×6.8 cm and weighing 160 g. This concretion consisted of central necrotic fatty tissue surrounded by concentrically laminated, acellular, fibrous material. Small PLBs usually do not require any specific treatment. However, if PLBs cause alimentary or urinary symptoms due to their large size, surgical removal may be recommended. It is essential for clinicians to be aware of this entity and its characteristic features to establish the correct diagnosis.
Peritoneal loose bodies (PLBs) are usually discovered during laparotomy or autopsy. It is generally agreed that these bodies are derived from the epiploic appendices via sequential processes of torsion, infarction, saponification, and calcification.1 In most cases, PLBs are asymptomatic and are no larger than a pea; they have little or no clinical significance and do not require any specific treatment.2 However, they occasionally grow to larger dimensions and cause symptoms such as intestinal obstruction and urinary retention.3-5 Here, we describe a case of a giant PLB incidentally found in the pelvic cavity of a 50-year-old man and its associated problems, and discuss how such a large body could develop.
A 50-year-old man underwent a routine medical examination, at which time multiple gallstones and an incidental pelvic mass were detected on computed tomography (CT) scanning of the abdomen and pelvis. An ovoid, well-defined mass in the pelvic cavity was detected consisting of central dense, heterogeneous calcifications and peripheral soft tissue (Fig. 1A). The mass compressed the bladder wall (Fig. 1B). There was a distinct fat plane around the mass, which did not appear to originate from or invade any of the adjacent organs. The patient denied any symptoms and the presence of any past medical problems. Laboratory tests were all within the normal range. Based on the radiologic findings, a preoperative diagnosis of peritoneal calcifying fibrous pseudotumor was suggested. On laparoscopic exploration, a well-circumscribed, fist-sized, hard, and free mass was found in the pelvic cavity. In addition, some of the epiploic appendices attached to the sigmoid colon were calcified with constricted stalks and were on the verge of becoming detached. All other abdominal and pelvic viscera were unremarkable. Laparoscopic cholecystectomy and pelvic mass removal were performed.
Grossly, the pelvic mass measured 7.5×7.0×6.8 cm and weighed 160 g; it was a white-to-pale yellow, hard, glistening concretion that looked like a boiled egg with the shell removed (Fig. 2A). The cut surface of the concretion revealed a central 1.5 cm-diameter nucleus of a creamy, cheese-like material surrounded by white-to-yellow lamellar structures (Fig. 2B). Microscopically, the concretion consisted of central necrotic fatty tissue (Fig. 2C) surrounded by many layers of concentrically laminated, eosinophilic, acellular, fibrous material (Fig. 2D) with scattered blue-to-black lakes of microcalcifications (Fig. 2E). Masson's trichrome stained the fibrous material blue, indicating an abundance of collagen (Fig. 2F). There were variable-sized vacuoles and empty clefts interspersed among the laminated material that could have represented vestiges of aged fat necrosis. The surface was partially lined by mesothelial cells. No inflammatory or foreign body reactions, parasites, polarizable substances, or identifiable tumor tissues were present in the specimen. These histopathological findings were characteristic of a giant PLB. The patient had an uneventful recovery. He was discharged from the hospital five days after surgery.
Although many possible etiologic factors have been proposed to explain the appearance of PLBs, it is widely believed that the most common cause of PLB is the chronic torsion of the epiploic appendix.1,6 The appendix may be attached by a thin pedicle that undergoes torsion, leading to infarction or aseptic fat necrosis. Thereafter, saponification and calcification of the fatty contents occur and the pedicle then atrophies. The epiploic appendix finally detaches from the colon and becomes a PLB. Over the years, the PLB becomes enlarged due to peritoneal reactions to this freely moving epiploic appendix as well as the depositions of peritoneal serum upon it. The center of the PLB thus contains necrotic fatty tissue with outer concentric zones of microcalcification surrounded by densely laminated, hyalinized, acellular fibrous tissue. In support of this hypothesis, previous reports have demonstrated that the size of PLB gradually increases. Donald and Kerr7 generated "peritoneal mice" in the laboratory by taking periuterine fat from guinea pigs. The "peritoneal mice" were placed in the peritoneal cavity of the same animals and typical PLBs were generated. The fibrous capsule of the PLBs was thicker in animals killed after 6 months than in animals killed after 12 days, indicating the slow growth of calcified layers around the necrotic center. In addition, Mohri et al.8 reported that the size of the PLB increased from 7.3×7.0 cm to 9.5×7.5 cm in a patient in a span of 5 years.
The clinical features of previously published cases are summarized in Table 1. The patients with PLB ranged in age from 2 months to 79 years at the time of diagnosis. Although there was no predilection for the location, the PLBs were mostly found to be free-floating in the pelvic cavity and tended to gravitate to the most dependent part of the abdominal cavity. The clinical presentation of the PLBs included small bowel obstruction, urinary tract infection, acute urinary retention, intermittent constipation, pelvic pain, and abdominal discomfort. Although the majority of PLBs range from 0.5 to 2.5 cm in diameter and generally cause no symptoms,7 they can reach a diameter of 5 to 9.5 cm and are then termed "giant" PLBs. Because of the limited room in the pelvic bowl, giant PLBs can compress pelvic structures, resulting in intestinal obstruction, incomplete bowel emptying, and urinary retention.3-5,9 The most common radiological finding of a PLB is an oval-shaped mass with a central calcification and a low-intensity area. On plain abdominal films, the appearance of a PLB has been described as a round or oval calcified mass with a mobile nature.6 CT scanning often reveals a concentric, round or oval well-defined mass with a central calcificationand surrounded by peripheral soft tissue.10 The correct diagnosis was preoperatively suggested in only one case,8 possibly due to the rarity of this entity. All but one patient underwent laparoscopic or open surgery for mass removal, and none of the patients developed a recurrence of the the PLB during the follow-up period.
Obviously, it is important to distinguish PLBs from other mobile lesions of the pelvic cavity such as calcified uterine leiomyomas, peritoneal calcifying fibrous pseudotumors, foreign body granulomas, desmoid tumors, teratomas, metastatic lesions of ovarian cancer, spontaneously amputated ovaries, fecaliths, lymphatic glands in the mesentery, nodal calcifications, tuberculosis, ecchinococcal cysts, urinary stones, and gallstones. Calcified uterine leiomyomas and peritoneal calcifying fibrous pseudotumors are especially hard to differentiate from PLBs because they also appear as round or oval masses in the pelvic cavity with soft tissue density and irregular calcifications. Furthermore, on magnetic resonance imaging, a PLB appears as a low-intensity mass on both T1- and T2-weighted images, and has the same intensity as muscle tissue or collagen fiber.11,12 However, unlike PLBs, both leiomyomas and calcifying fibrous pseudotumors are enhanced with contrast, which can discriminate these lesions from PLBs. In addition, since PLBs are freely mobile, additional scanning with the patient in the prone position or a follow-up imaging study can demonstrate a change of mass location, facilitating the diagnosis with higher confidence. Surgical removal with histological examination can definitively confirm the diagnosis based on the characteristic morphological features of PLBs.
To date, a few cases of giant PLBs have been reported in the literature.2-5,8,9,11-13 Even though these patients were asymptomatic, surgery was performed to remove the suspected neoplasm. Considering the nature of the lesion, no specific treatment is required in asymptomatic patients. However, if there is a pelvic mass of obscure origin, or if it becomes associated with alimentary or urinary symptoms due to its large size, surgical exploration and removal may be recommended. It may be better to treat these patients laparoscopically.
In summary, we describe a case of a giant PLB found incidentally and discuss its diagnostic features. Even though giant PLBs are extremely rare, they should be considered in the differential diagnosis of a mobile lesion in the pelvis and abdomen. If they cause alimentary or urinary symptoms due to their large sizes, surgical removal may be recommended. It is important for radiologists and clinicians to be aware of this rare entity and its characteristic features to establish the correct diagnosis.
The views and opinions expressed in this article are those of the authors and do not reflect the official policy or position of the Republic of Korea Air Force or Republic of Korea Ministry of National Defense.

No potential conflict of interest relevant to this article was reported.

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Fig. 1
Abdominopelvic computed tomography findings. (A) Axial image shows a large, oval-shaped mass (arrow) consisting of peripheral soft tissue and central dense, heterogeneous calcifications. There is a distinct fat plane separating the mass from the adjacent organs. (B) Sagittal image reveals that the mass (arrow) compresses the bladder wall.
Fig. 2
Gross and histologic findings. (A) Grossly, the mass is an egg-shaped, white-to-pale yellow, hard, glistening concretion, measuring 7.5×7.0×6.8 cm, weighing 160 g, and resembling a boiled egg. (B) The cut surface of the concretion reveals a 1.5 cm diameter central portion of gray-to-yellow, creamy material surrounded by concentrically lamellar structures. (C) Microscopically, the central portion (inset) of the concretion consists of necrotic fatty tissue. (D) The peripheral portion consists of many layers of laminated, acellular, fibrous material. (E) Scattered blue-to-black lakes of microcalcifications are also identified in the peripheral portion. (F) Masson's trichrome staining shows intensely staining collagen at the periphery.
Table 1.
Summary of the clinical information of patients with PLB
Authors Age/Sex Presenting symptoms or signs Imaging findings Preoperative diagnosis Maximal diameter (cm) Location Surgical approach
Burns and Rogers [14] 33 yr/F Pelvic pain Calcified mass Not available 1.8 LUQ Open
Bhandarwar et al. [5] 65 yr/M Acute uninary retention Concentric radio-opaque shadow Not available 9.0 RVP Open
Takada et al. [2] 79 yr/M Incidental Calcified mass Leiomyoma 7.0 RVP Open
Nomura et al. [12] 63 yr/M Incidental Egg-shaped mass with calcification Leiomyoma 5.0 PC Laparoscopy
Asabe et al. [15] 2 mo/F Uninary tract infection Cystic mass with calcification Not available 3.0 PC Laparoscopy
Ooyagi et al. [16] 65 yr/M Abdominal discomfort Egg-shaped mass with calcification Not available 4.0 RLQ Not available
Takabe et al. [3] 68 yr/M Small bowel obstruction Oval-shaped stone with calcification Gallstone ileus 4.2 RLQ Open
Ghosh et al. [4] 63 yr/M Small bowel obstruction Oval-shaped stone with calcification Gallstone ileus 5.8 PC Open
Mohri et al. [8] 73 yr/M Abdominal pain Oval-shaped stone with calcification Peritoneal loose body 9.5 RVP Open
Takayama et al. [11] 63 yr/M Abdominal discomfort Egg-shaped mass with central low-intensity area Not available 4.5 PC Laparoscopy
Koga et al. [17] 33 yr/F Infertility Oval-shaped filling detect Not available 3.0 VUP Laparoscopy
Hedawoo and Wagh [13] 65 yr/M Intermittent constipation Heterogeneously enhancing mass with calcification Duplication cyst 9.5 RLQ Open
Gayer and Petrovitch [10] 59 yr/M Incidental Round mass with calcification Metastatic tumor 3.0 PC Not available
Sewkani et al. [9] 64 yr/M Small bowel obstruction Not available Not available 7.0 PC Open
Jang et al. [18] 60 yr/M Incidental Oval-shaped mass with calcification Leiomyoma 4.5 PC Laparoscopy
Nozu and Okamura [19] 67 yr/M Incidental Well-defined mass with a central low-intensity area Pancreatic cancer 4.0 PC Not available
Present case 50 yr/M Incidental Oval-shaped mass with calcification Calcifying fibrous pseudotumor 7.5 PC Laparoscopy

F, female; LUQ, left upper quadrant; M, male; RVP, rectovesical pouch; PC, pelvic cavity; VUP, vesicouterine pouch; RLQ, right lower quadrant.

Figure & Data



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