Lesson 25

Infectious catarrhal colitis, microscopic

Infectious agents such as Shigella, Salmonella, and Campylobacter can produce an acute self-limited colitis with cryptitis, crypt ulcers, and extensive infiltrates of neutrophils and lymphocytes between crypts, as shown here. Additional findings can include edema, abscesses, and small granulomas. The crypt architecture and goblet cells are preserved, unlike in inflammatory bowel disease. Resolution typically occurs within 2 to 3 weeks.

Pseudomembranous colitis, microscopic

The underlying colonic mucosa is intact, so grossly bloody diarrhea is unlikely, but there is a  marked overlying exudate with necrotic epithelial cells admixed with inflammatory cells. The exudate within crypts may be so extensive that it erupts from the surface in volcano-like fashion. C. difficile toxins disrupt the epithelial cytoskeleton, with loss of tight junction barrier function, and promote cytokine release and apoptosis. Recurrent infection may occur.

Typhoid ileitis, "clear" ulcer, microscopic

Ulceration of mucosa with fibrinoid necrosis of epithelial layer provoked by the release of the potent endotoxin. Exactly under the debris there is one clearly visible typhoid nodule (granuloma) composed of the macrophages with abundant clear cytoplasm. In underlying Payer's patch the replacement of lymphocytes by monocytic derivatives has found.