MR Findings in a Rare Case of Sclerosing Mesenteritis of the Mesocolon

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Jemimah Watts
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1 JOURNAL OF MAGNETIC RESONANCE IMAGING 21: (2005) Clinical Note MR Findings in a Rare Case of Sclerosing Mesenteritis of the Mesocolon Nadir Ghanem, MD,* Gregor Pache, MD, Thorsten Bley, MD, Elmar Kotter, MD, and Mathias Langer, MD Sclerosing mesenteritis is a rare, usually benign disorder of the mesentery. Depending on the predominant tissue component (inflammation, fat, or fibrosis), it is known as mesenteric panniculitis or retractile mesenteritis. We present a rare case of retractile mesenteritis of the mesocolon as a cause of severe abdominal pain. US, CT, and MRI were the imaging modalities used. We emphasize the MR finding of a fibrous capsula in retractile mesenteritis, as this is to our knowledge the first study to describe this entity. This finding may be valuable for establishing a diagnosis of sclerosing mesenteritis, as well as for differentiating this disease from other mesenteric diseases. Key Words: MRI; CT; abdominal pain; sclerosing mesenteritis; mesocolon J. Magn. Reson. Imaging 2005;21: Wiley-Liss, Inc. SCLEROSING MESENTERITIS is a rare, usually benign disorder that affects the mesenteric adipose tissue (1 4). Two forms of the disease are known: mesenteric panniculitis (if the lesion is histologically characterized more by inflammation and fat necrosis than by fibrosis), and retractile mesenteritis (when the lesion is characterized by predominant fibrosis) (3,5). The disease usually involves the mesentery of the small bowel, particularly at its root, but can rarely involve the mesocolon (1,3). CT has proven to be helpful in suggesting a diagnosis of sclerosing mesenteritis and distinguishing it from other mesenteric diseases; however, biopsy is still often necessary to exclude malignancy (3,4). In this report, we present the radiologic findings in an interesting rare case of a female patient with a retractile mesenteritis located in the mesocolon. We emphasize the MR finding of a fibrous capsula in retractile mesenteritis, which may be valuable for making a differential diagnosis. Department of Diagnostic Radiology, University Hospital Freiburg, Freiburg, Germany *Address reprint requests to: N.G., Department of Diagnostic Radiology, Hugstetter Strasse 55, Freiburg, Germany. gha@mrsl.ukl.uni-freiburg.de Received April 26, 2004; Accepted December 16, DOI /jmri Published online in Wiley InterScience ( CASE REPORT A 20-year-old female with a medical history of hepatitis C consulted our hospital with progressively worsening abdominal pain located in the mid-epigastric region, vomiting, and diarrhea for 3 days. Except for oral contraceptives, she took no medication. Her history was negative concerning previous operations or severe trauma. On physical examination her abdomen was soft, but there was pain on pressure in the left middle and upper abdomen. Peristaltic bowel movement was normal. Admission laboratory data showed an inflammatory reaction with a white blood cell count of 12,200/ l (normal: ,000/ l) and a C-reactive protein of 21.8 mg/dl (normal: 0.5 mg/dl); however, chemical values, and liver and pancreatic enzymes were within the normal range. Ultrasound (US) depicted a cm ovoid mass of regular shape located in the mesenterium, which showed intermediate echogenity (Fig. 1). Contrast-enhanced CT with orally administered contrast media demonstrated an ovoid tumorous formation ( cm) in the left upper abdomen (CT attenuation values ranged from 12 to 68 HE), with no signs of invasiveness or displacement of the bowel loops. The lesion showed a hyperdense rimlike enhancement. No lymphadenopathy was found (Fig. 2). Enteroclysis showed a slight distension of the proximal jejunal loops with no signs of a tumorous lesion (not shown). A colonoscopy showed no pathologic findings. A gynecological examination revealed free fluid in the pouch of Douglas, with no further pathologic findings. The patient recovered rapidly under an antibiotic therapy with cefotiam and metronidazole for 7 days; however, a control US again showed the mesenterial mass. For further evaluation, an MRI of the abdomen (1.5 Tesla MR unit, Magnetom Symphony; Siemens Medical Solutions, Erlangen, Germany) was conducted, which revealed a 4-cm tumor in the left upper abdomen. With the use of an unenhanced T1-weighted gradient recalled echo (GRE) sequence (TR-148, TE-4.8, matrix size , SL-6 mm), the tumorous lesion showed a central signal increase indicative of intratumoral bleeding (Fig. 3a). The T2-weighted images (TR-3165, 2005 Wiley-Liss, Inc. 632

The tumor was resected in toto out of the mesocolic layer. The postoperative course was unremarkable, and the patient was dismissed on day 6.

2 Sclerosing Mesenteritis of the Mesocolon 633 after her first admission. A laparotomy identified a tumor, 3 cm in diameter, in the mesocolon next to the medial colic artery, with a fibrous cord leading to the upper jejunum. The tumor was resected in toto out of the mesocolic layer. The postoperative course was unremarkable, and the patient was dismissed on day 6. A histologic examination revealed a cm specimen completely covered by a capsula, representing a fibrous fat tissue necrosis showing signs of previous hemorrhage and localized inflammation, with no signs of malignant growth. Up to now, the clinical follow-up has been uneventful. Figure 1. Ultrasound depicted a cm ovoid mass of regular shape located in the mesenterium, which showed intermediate echogenity and an adjacent small cystic lesion. TE-120, matrix size , SL-6 mm) revealed a hyperintense signal alteration in the central portion of the tumor, surrounded by an intermediate signal and a hypointense capsula (Fig. 3b), which showed strong enhancement after i.v. contrast administration of Gd- DTPA (Magnevist ; Schering, Berlin, Germany) with a T1-weighted GRE fat-suppressed sequence (TR-168, 4.8, matrix size , SL-6 mm) (Fig. 3c). A CT-guided biopsy was performed to rule out malignancy. Unfortunately, the biopsy findings were unclear, and therefore an operation was performed two weeks DISCUSSION Sclerosing mesenteritis is a rare, usually benign disorder that affects the mesenteric adipose tissue (1 4). The acute form is defined as mesenteric panniculitis, and is histologically characterized more by inflammation and fat necrosis than by fibrosis. The chronic form, which is referred to as retractile mesenteritis, is characterized by predominant fibrosis. Sclerosing mesenteritis is the accepted term because fibrosis is always present to some extent (3,4). The disease usually involves the mesentery of the small bowel, particularly at its root, but can rarely involve the mesocolon (1,4). A review of 20 patients with mesocolic lesions indicated that the sigmoid colon was most often involved (65%) (1). The presence of the lesion in the transverse colon, as in the current case, has been described in only a very few studies in the literature (1 3). The etiology of this disease remains unknown; however, possible causative factors have been suggested, including ischemia, infection, previous trauma, and autoimmune disorders (1,3,4). Sabate et al (3) found an association with previous abdominal surgery in nine of 17 patients with sclerosing mesenteritis. In a study by Daskalogiannaki et al (5), 34 of 49 patients (69.3%) had a coexisting malignancy, mostly urogenital or gastrointestinal lymphomas. Figure 2. Contrast-enhanced CT with orally administered contrast media demonstrated an ovoid tumorous formation ( cm) in the left upper abdomen (CT attenuation values ranged from 12 to 68 HE). The lesion showed a hyperdense rimlike enhancement (arrow).

Figure 3. a: An unenhanced T1- weighted GRE sequence (TR-148/TE- 4.8) shows a subtle, central signal increase within the tumorous lesion indicative of intratumoral bleeding (arrow).

3 Figure 3. a: An unenhanced T1- weighted GRE sequence (TR-148/TE- 4.8) shows a subtle, central signal increase within the tumorous lesion indicative of intratumoral bleeding (arrow). The ring-like focus of increased signal represents fibrous and fatty tissue, indicating reactions of mesenteritis (arrowheads). b: An unenhanced T2- weighted image (TR-3165/TE-120) in the coronal plane reveals a hyperintense signal alteration in the central portion of the tumor (star) surrounded by an intermediate signal and a hypointense capsula (arrow). c: A T1-weighted image (TR-168/TE 4.8) shows strong enhancement of the capsula and the adjacent inflammatory tissue after i.v. contrast administration of Gd-DTPA (arrow).

4 Sclerosing Mesenteritis of the Mesocolon 635 The clinical presentation includes abdominal pain, vomiting, diarrhea, an abdominal mass, or rectal bleeding. However, patients can also be completely asymptomatic (3,4). Only a very few cases with US evaluation of sclerosing mesenteritis have been reported (6). As in the current case, US depicted an echogenic mass with hypoechoic areas. Sato et al (6) described three patients in whom the mass was poorly margined. This is in contrast to previous reports and to the current case, in which a well defined mass was found (6). The CT findings of the two major disease forms of sclerosing mesenteritis were previously described by Sabate et al (3). Mesenteric panniculitis usually presents as a heterogeneous mass with a large component of fat, whereas retractile mesenteritis has a more homogeneous appearance with a greater proportion of soft-tissue density, as we found in our case (Fig. 2). Sabate et al (3) stressed the importance of two imaging findings in mesenteric panniculitis: the fat ring sign and the presence of a tumoral pseudocapsula. The latter is caused by a peripheral band of soft-tissue attenuation that separates the normal mesentery from the the inflammatory process and it was found in 50% (n 12) of the patients with mesenteric panniculitis, but in none of the patients with retractile mesenteritis (n 5). Our CT findings showed a peripheral band of soft-tissue attenuation almost entirely around the lesion. The preservation of fat around the mesenteric vessels is called the fat ring sign. Sabate et al (3) observed this feature exclusively in patients with mesenteric panniculitis (75% of the cases). In the current case, we did not detect a fat ring sign. The MRI features of mesenteric panniculitis were previously described by Kobayashi et al (7) and Fujiyoshi et al (8). These authors stressed that mesenteric panniculitis is characterized by a high signal intensity in comparison with the concomitant subcutaneous and peritoneal fat. This may indicate that mesenteric panniculitis consists mainly of a waterequivalent substance rather than pure fatty tissue. This is in concordance with our MRI findings in T2- weighted images that demonstrated a well-surrounded hyperintense lesion (Fig. 3b). Kronthal et al (9) reported a case of sclerosing mesenteritis in which they found low signal intensity on T2-weighted images, which is most compatible with fibrosis. Interestingly, we found a hypointense capsula on T2- weighted images that showed strong enhancement after i.v. contrast administration of Gd-DTPA (Fig. 3b and c), which is suggestive of a fibrotic capsula. The centrally located hyperintense area on the T1- weighted images indicates blood. The histologic finding of a fibrous cord and a surrounding fibrotic capsula indicates a later, chronic stage of the disease. This correlates well with the finding of a mass with more soft-tissue density on CT. Of particular note is the finding of a fibrous capsula in retractile mesenteritis in our patient. The fibrous capsula was detected on MRI, whereas on CT the real fibrous capsula could not be differentiated from a tumoral pseudocapsula. In contrast to our findings, Sabate et al (3) indicated that the tumoral pseudocapsula disappears when mesenteric panniculitis evolves into retractile mesenteritis (3). This raises the question as to whether the change from a pseudocapsula into a real fibrous capsula, separating the lesion from healthy tissue, is one way of marking the transition from mesenteric panniculitis into retractile mesenteritis, thereby affecting the clinical prognosis. Although with medical treatment sclerosing mesenteritis usually has a benign course and favorable outcome, progressive fibrosis may result in scarring, with retraction of the mesentery that can lead to ischemia or obstruction and consequently surgery (3,10). It has been suggested that colonic forms have a more aggressive course and require surgical treatment more often than other forms (11). Infiltrating fibrosis may lead to thrombosis of the mesenteric vessels with secondary varicel bleeding (10). This may explain the central hemorrhage seen on the CT, MRI, and histologic findings. The differential diagnosis of mesenteric panniculitis includes inflammatory pseudotumor, Crohn s disease with fibrofatty proliferation, and fatty tumors such as lipoma or liposarcoma (3,10). Occasionally, epiploic appendices can be involved in colonic lesions (1). Several conditions can mimic the CT appearance of retractile mesenteritis, including carcinoid and desmoid tumors, carcinomatosis, and lymphoma (10). Therefore, histological sampling, which often requires open surgical biopsies, is currently needed for a definitive diagnosis. Our MR findings of a fibrotic capsula may be instrumental in clarifying a mesenterial mass, and may help to avoid biopsy or surgery. Concerning the etiology of the sclerosing mesenteritis in the case presented, we can only speculate. The patient had no history of trauma or surgery, but she did suffer from a chronic hepatitis C infection. Additionally, since we did find a fibrous duct connecting the mass of the mesocolon with the upper jejunal wall, previous strangulation of the mesocolon by a bride may be a possible explanation for a localized necrosis. CONCLUSIONS In summary, we have presented a very rare case of retractile (sclerosing) mesenterits of the mesocolon as a cause of severe abdominal pain. To our knowledge this is the first study to describe the MR finding of a peripheral, fibrous capsula in retractile mesenteritis. This finding may be valuable for differentiating the two forms of sclerosing mesenteritis, and distinguishing sclerosing mesenteritis from mesenteric neoplasms. REFERENCES 1. Adachi Y, Mori M, Enjoji M, Ueo H, Sugimachi K. Mesenteric panniculitis of the colon. Review of the literature and report of two cases. Dis Colon Rectum 1987;30:

5 636 Ghanem et al. 2. Durst AL, Freund H, Rosenmann E, Birnbaum D. Mesenteric panniculitis: review of the literature and presentation of cases. Surgery 1977;81: Sabate JM, Torrubia S, Maideu J, Franquet T, Monill JM, Perez C. Sclerosing mesenteritis: imaging findings in 17 patients. AJR Am J Roentgenol 1999;172: Horton KM, Lawler LP, Fishman EK. CT findings in sclerosing mesenteritis (panniculitis): spectrum of disease. Radiographics 2003;23: Daskalogiannaki M, Voloudaki A, Prassopoulos P, et al. CT evaluation of mesenteric panniculitis: prevalence and associated diseases. AJR Am J Roentgenol 2000;174: Sato M, Ishida H, Konno K, et al. Mesenteric panniculitis: sonographic findings. Abdom Imaging 2000;25: Kobayashi S, Takeda K, Tanaka N, Hirano T, Nakagawa T, Matsumoto K. Mesenteric panniculitis: MR findings. J Comput Assist Tomogr 1993;17: Fujiyoshi F, Ichinari N, Kajiya Y, et al. Retractile mesenteritis: small-bowel radiography, CT, and MR imaging. AJR Am J Roentgenol/1997;169: Kronthal AJ, Kang YS, Fishman EK, Jones B, Kuhlman JE, Tempany CM. MR imaging in sclerosing mesenteritis. AJR Am J Roentgenol 1991;156: Sheth S, Horton KM, Garland MR, Fishman EK. Mesenteric neoplasms: CT appearances of primary and secondary tumors and differential diagnosis. Radiographics 2003;23: Ikoma A, Tanaka K, Komokata T, Ohi Y, Taira A. Retractile mesenteritis of the large bowel: report of a case and review of the literature. Surg Today 1996;26:

Curious case of Misty Mesentery

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