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Case Report |
1
Russell H. Morgan Department of Radiology and Radiological Science, Johns
Hopkins University, 601 N. Caroline St., Rm. 3254, Baltimore, MD 21287.
2
Department of Pathology, Johns Hopkins Medical Institution, 600 N. Wolfe St.,
Baltimore, MD 21287.
Received February 7, 2001;
accepted after revision May 25, 2001.
Address correspondence to E. K. Fishman.
Introduction
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Dual-phase abdominal CT was performed. On a Plus 4 Volume Zoom multidetector CT scanner (Siemens Medical Systems, Iselin, NJ), the abdomen was imaged at 1-mm collimation and 1.25-mm slice thickness using 1-mm data reconstruction with a pitch of 6. Water (750 mL) was given orally as a negative contrast material with 125 mL of Omnipaque 350 ([iohexol] Nycomed Amersham, Princeton, NJ) administered IV at a rate of 3 mL/sec. Scanning delays were 25 and 50 sec for imaging of the arterial and venous phases, respectively. Three-dimensional volume rendering was subsequently performed on a prototype three-dimensional Virtuoso workstation (Siemens Medical Systems).
A single large, lobulated, minimally enhancing mass of homogeneous soft-tissue density was found in the root of the mesentery. Mesenteric stranding was seen (Fig. 1A), but no bowel involvement was present. The mass extended caudad and encased the superior mesenteric artery and vein for most of their respective lengths (Figs. 1B and 1C). The caliber of the superior mesenteric artery was reduced but patent, with preservation of the densitometric values of adipose tissue immediately adjacent to it (i.e., a fatty halo) (Figs. 1A and 1C), and the jejunoileal branches were encased (Fig. 1D). The superior mesenteric vein was occluded, and the splenic vein was nearly occluded at the portal confluence, with varices noted around the stomach and liver (Fig. 1B). A focus of coarse calcifications (Figs. 1B and 1C) was seen toward the caudad aspect of the mass. No adenopathy was seen. Carcinoid tumor and mesenteric lymphoma were among the differential considerations.
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Two separate sonographically guided fine-needle aspiration and core needle biopsies were nondiagnostic. Exploratory laparotomy was performed, and the mass was located in the mesentery and confirmed to be nonresectable. Excision biopsies were performed. The pathology findings were of a polyclonal lymphoplasmacytic population of cells with collagen, consistent with a diagnosis of sclerosing mesenteritis (Figs. 1E and 1F).
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Sclerosing mesenteritis is grouped among idiopathic fibrosclerotic disorders and inflammatory pseudoneoplasms, which include entities such as retroperitoneal fibrosis, sclerosing cholangitis, Riedel's thyroiditis, and orbital pseudotumor. The exact nosologic and pathologic relationships of sclerosing mesenteritis to these disorders are unknown. What unifies these conditions is that they are all masses leading to displacement of surrounding structures or to organ dysfunction caused by compressive growth, and all have histologic findings limited to chronic inflammation and fibrosis [3]. Clinical links may also exist, because many of the conditions coexist in a single patient or have familial trends. Suggested causes are many and varied, with autoimmunity commonly suggested.
Sclerosing mesenteritis, by definition, is a mass that is often obscured in the leaves of the mesentery. The clinical, imaging, and intraoperative findings are imperative to complement the diagnosis of the nonspecific histologic features that can also be seen in lymphomas or in soft tissue adjacent to infiltrating carcinomas. Frequently, as in our patient, surgery is required for excision biopsy, but vessel compromise will limit any further dissection of the mesentery for exposure or resection. Thus, imaging findings assume greater importance; when imaging is performed, the goals must be to define the mass location and extent, characterize it, and document the extent of vessel or bowel involvement. The end points are to provide guidance for biopsy and to provide gross findings to aid the pathologist and possibly to direct surgical plans for resection or relief of complications.
The axial CT imaging features of sclerosing mesenteritis and its differential diagnoses have been well described [4, 5]. Many CT features of this disorder are shared by mesenteric lymphoma, carcinoid, undifferentiated carcinoma, and desmoid tumor. Lymphadenopathy may prompt a consideration of lymphoma, but calcification occurs in both lymphoma and carcinoid. Desmoid tumors are usually related to some prior injury or trauma and are often found in association with Gardner's syndrome and colonic polyposis. Omental involvement may mimic carcinomatosis, tuberculosis, and primary mesenteric mesothelioma. A primary pancreatic neoplasm may present diagnostic difficulty unless a clear plane of separation is identified [6]. The CT "fat ring" sign has been suggested to imply the more acute subset of mesenteric panniculitis [4], although our case is at variance with this. Our patient had a clear preservation of adipose densitometric values in a halo distribution around the superior mesenteric artery on axial and volume-rendered images (Figs. 1A and 1B) and yet represents an older patient with a chronic history and a predominance of collagen fibrosis consistent with the chronic retractile mesenteritis form of the disease [1].
The growth pattern of sclerosing mesenteritis is limited only by a flimsy mesentery into which it variably insinuates, expands, and retracts, leading to vessel encasement and compromise. Thus, the gross features of sclerosing mesenteritis do not lend themselves easily to a single axial plane. With current multidetector technology, the near-isotropic data sets produced allow an infinite number of other imaging planes with high fidelity and comparable quality to the original axial images [7], helping "open up" tissue planes to clarify bowel or visceral involvement. In some cases, volume-rendered data can also be reformatted to produce images like those of enteroclysis or urography to complement the mesenteric study in which bowel or ureteric compromise are also a concern. Revealing the extent of pathology for the clinicians was facilitated by displaying the mass in its entirety on single sagittal and coronal images (Figs. 1B,1C,1D).
The angiograms generated by multidetector CT allow high-resolution images without compromising z-axis coverage in a single breathhold. Rapid infusion of IV contrast material and overlapping reconstruction enable three-dimensional visualization of vessel branches as far as the mesenteric border (Fig. 1D). Unlike the threshold techniques of shaded-surface display and maximum intensity projection, the volume-rendered technique uses all the acquired data, and the percentage-based classification preserves the Hounsfield attenuation of the various soft-tissue types so that the mass and its vascular relationship are depicted [8] (Figs. 1B,1C,1D). In this case, the mesenteric angiogram showed occlusion of the superior mesenteric vein and collateral development (Fig. 1B); and oblique coronal planes defined encroachment on the patent small, curving, axial in-plane jejunoileal branches that demarcated the actual leaves of the small bowel mesentery (Fig. 1D). No further vascular studies were required.
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