Imaging Studies
Characterization of mesenteric tumors on the basis of imaging features can be accomplished by means of computed tomography (CT) and magnetic resonance imaging (MRI), which can provide important information regarding size, gross nature, and involvement of adjacent structures, as well as permitting inferences regarding the histopathologic nature of the tissue. [29, 30, 18, 20] Localization of a mass to mesentery is generally possible in this way. CT and MRI can distinguish between solid and cystic masses and can identify metastatic disease in the abdomen or chest in advanced disease.
Abdominal computed tomography
Abdominal CT can be strongly suggestive of the diagnosis of lipoma as opposed to other solid tumors, though liposarcoma cannot be completely excluded on the basis of appearance on CT, particularly with very large lesions. Benign fatty tumors are usually homogeneous and have the density of normal mesenteric fat (see the image below). Lack of homogeneity or infiltrative processes that surround mesenteric vessels and lymph nodes should increase suspicion of malignant disease. To some extent, tumor vascularity can also be characterized with the administration of intravenous (IV) contrast during imaging.
CT image of benign mesenteric lipoma. This discrete lesion (arrows) is homogeneous and has density of normal surrounding mesenteric fat.
Magnetic resonance imaging
MRI is sometimes used alone or in conjunction with other imaging methods to help characterize mesenteric masses. It provides information similar to that provided by CT but is better able to define tissue characteristics (eg, fatty vs fibrotic features) with high sensitivity. Direct comparisons of CT with MRI in the examination of mesenteric masses are lacking; however, MRI may be of great diagnostic value, particularly in patients with mesenchymal tumors. Diffusion-weighted sequencing, as compared with standard unenhanced MRI enterography, may improve visualization of mesenteric tissues and allow detection of both tumors and nonneoplastic masses. [31]
A study by Low et al found dynamic contrast-enhanced (DCE) MRI to yield better depiction of small-volume mesenteric tumors. [32] Ezhapilli et al described a systematic approach to characterization of mesenteric masses based on MRI characteristics that could provide a stepwise basis for defining possible diagnoses and aiding in the formulation of treatment plans. [20]
Arteriography
Arteriography is seldom used as a preoperative study in patients with mesenteric tumors unless there is a significant possibility that vascular involvement by the tumor may greatly complicate operative management. This procedure may define areas of mesenteric arterial blood supply that are compromised by tumor and may suggest the need for either extensive bowel resection with the mesenteric mass or arterial reconstruction.
Ultrasonography
The successful use of ultrasonography (US) to characterize mesenteric masses is well described, particularly as regards the ability of US to distinguish cystic from solid features. US is far less frequently employed for diagnostic characterization than CT and MRI, which provide significantly more anatomic information and are not as subject to operator-dependent technique and interpretation issues.
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Massive mesenteric cyst that proved to be multiloculated lymphangioma. This large but benign structure had developed on narrow attachment to base of small-bowel mesentery and was amenable to excision without endangering any other mesenteric structures.
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Cluster of enlarged lymph nodes (arrows) in small-bowel mesentery, which on laparoscopic biopsy proved to be B-cell (follicular) lymphoma.
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Mesenteric lymph node mass with metastatic involvement of small-bowel carcinoid. This was resected en bloc along with segment of small bowel within arterial blood supply distribution affected by removal of mass. This small intestine contained subcentimeter primary carcinoid tumor.
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Axial contrast-enhanced MRI of central hyperintense fatty mesenteric mass with preservation of fat around vessels and lymph nodes with "fat ring" or “halo” sign (arrows) consistent with mesenteritis. Courtesy of BioMed Central Ltd, Springer Nature [Arda K, Kizilkanat KT, Aydin H. CT and MRI aspect of mesenteric panniculitis. J Case Rep Med 7. 2018 Jun 30.]
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CT image of increased mesenteric tissue density or “misty mesentery” (between arrows), which laparoscopic incisional biopsy demonstrated was sclerosing mesenteritis.
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CT image of benign mesenteric lipoma. This discrete lesion (arrows) is homogeneous and has density of normal surrounding mesenteric fat.
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Laparoscopic view of simple mesenteric cyst before laparoscopic excision.
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Laparoscopic view of simple mesenteric cyst dissection bed after laparoscopic excision.
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Mesenteric GIST-like tumor with solid and cystic components. Diagnosis was established after resection with demonstration of absence of primary GI tumor.
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Resected mesenteric tumor. Operative treatment involved segmental small-bowel and colon resection. Large specimen size is evident.
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Section of malignant mesenteric fatty tumor resected en bloc with obstructed, encased small intestine.
