Today's Veterinary Practice

MAR-APR 2018

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PEER REVIEWED 68 IMAGING ESSENTIALS Hemangiosarcoma causes luminal narrowing and has been identified in the colon and rectum of cats. 18,19 Gastrointestinal stromal tumors arise from the interstitial cells of Cajal; these are cells that regulate intestinal motility and peristalsis. They have histologic features similar to that of intestinal smooth muscle tumors but can be distinguished by immunohistochemistry. 29 The predilection sites for these tumors are the cecum and colon, whereas, smooth muscle tumors are more likely to be affect the stomach and small intestine. 29 Gastrointestinal stromal tumor has been described in the feline jejunum as a hypoechoic mass with heterogeneous regions. 30 Benign Neoplasms Adenomatous polyps are infrequently seen lesions that have been identified in the rectum of dogs and small intestines of cats. 15,25 They appear as small, round to ovoid, mixed or varying echogenicity, pedunculated or broad based structures extending into the intestinal lumen; they can arise from the mucosal or submucosal surfaces. 31-34 There is a great potential for malignant transformation if they are large ( FIGURE 11 ). Nonneoplastic Wall Thickening Nonmalignant diseases, such as histiocytic, 35 granulomatous, 36 and fungal 37 colitis, can cause focal wall thickening or masses. Eosinophilic sclerosing fibroplasia has been described in the ileocecocolic junction and the colon of cats ( FIGURE 12 ); 38,39 these lesions appear as masses or focal wall thickening with a loss of normal wall layering, similar to neoplastic lesions. 39 Pythiosis can cause multifocal pyogranulomatous infections of the colon, causing focal wall thickening with a loss of wall layering, although an eccentric colonic mural mass was identified in one dog. 40 FIGURE 12. Short axis view of the ileum of a cat diagnosed with eosinophilic sclerosing fibroplasia. Note the circumferential thickening of the muscularis layer ( white arrowhead ) of the ileum. FIGURE 11. Long axis view of the descending colon and rectum of a dog diagnosed with an adenomatous polyp. Secondary to the mass protruding into the colonic lumen, note the focal thickening, loss of wall layering, and distortion of the hyperechoic gas interface. FIGURE 13. Long axis view of the colon of a cat diagnosed with severe pyogranulomatous colitis (A). Note the thickened wall and loss of wall layering. In cases with severe colitis, ultrasonographic appearances are indistinguishable from neoplastic infiltration. Long axis view of the colon of a dog diagnosed with epithelial hyperplasia and neutrophilic inflammation of the colon (B). Note the thickened but preserved layering of the wall. A B

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