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Histologically, which findings help differentiate infectious colitis and NSAID-associated colitis? Infectious colitis on histologic examination shows acute inflammation in the lamina propria with cryptitis, crypt abscesses, and lack of prominent chronic inflammatory infiltrate or basal plasmacytosis (as seen in IBD). Chronic architectural changes may not be pronounced. Causative organisms include Escherichia coli O157:H7, Salmonella, Shigella, Clostridium, Campylobacter, Yersinia, cytomegalovirus colitis, …

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Differential diagnosis of pseudomembranes Pseudomembranous colitis is a complication of antibiotic-associated colitis caused by C. difficile . Not all C. difficile infections produce pseudomembranous colitis. Grossly, discrete gray-white patches of pseudomembranes are identified. The histologic features include loosely adherent fibrinopurulent exudate on the luminal surface (pseudomembrane) with associated superficial mucosal necrosis. Features of Ischemic colitis damage include mucosal necrosis, hemorrhage with congestion …

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Differential diagnosis of focal active colitis Infectious colitis Crohn’s disease UC early or resolving Bowel preparation artifact

Colitis associated dysplasia in IBD Dysplasia can be flat or form a mass (dysplasia-associated lesion or mass [DALM]). Dysplasia in UC is graded as negative, indefinite, low grade, or high grade. The differential diagnosis of DALM is sporadic adenoma. The distinction between the two is difficult and requires clear communication between the pathologist and the endoscopist. If the …

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What are the histologic features of idiopathic inflammatory bowel disease (IBD)? Chronic ulcerative colitis (UC): Grossly, there is diffuse involvement of rectosigmoid and left-sided colon, and proximal extent of the disease varies. Infections such as Cytomegalovirus, Salmonella, Shigella, and Clostridium difficile can complicate UC. Toxic megacolon is a fulminant acute complication of the disease. Histologically, the features of acute disease …

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Neuroendocrine tumors Carcinoid tumor: The duodenum is the most common site of these well-differentiated neuroendocrine tumors. These can be functional or nonfunctional in the production of hormones. Serotonin production is common in ileal carcinoids. Gastrin production is common in duodenal carcinoids. Immunohistochemical stains cannot be used to predict the functional status of the tumor. All carcinoids …

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Causes of infectious enteritis Giardiasis: Giardia lamblia is seen as a pear-shaped organism, which resides in the upper small intestine (duodenum and jejunum) and exists in two forms—trophozoite and cyst. The trophozoite form (7 μm wide, 14 μm long) shows two symmetrical nuclei with nucleoli and four pairs of flagella. On longitudinal sections, it appears as …

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