| Summary: | Histopathology can play an important role in diagnosing infictious
colitis for several reasons. First, colonic mucosal biopsy can often reliably
differentiate acute self limited colitis (ASLC). or infectious type colitis, from
idiopathic inflammatory bowel disease (IBD). In ASLC, crypt architecture is
normal and the inflammatory infiltrate in the lamina propria predominantly
acute, ie, polymorphonuclear cells. In IBD, in contrast, crypt architecture is often
abnormal nd the inflammatory infiltrate in the lamina propria in both acute and
chronic, ie, polymorphonuclear cells, plasma cells ,and lymphocyte are present
in increased numbers. Second, biopsy may give a clue to the specific infection.
Biopsy may reveal the presence of specific parasites such as Entamoeba histolytica,
cryptosporidia or schistosomiasis. Viral inclusions are seen when cytomegalovirus or herpes simplex type II virus infect the colon. Granulomas usually indicate
Crohn's disease but can he seen with infections due to Chlamydia trachomatis,
Treponema pallidum and Mycobacterium tuberculosis. Both chlamydial and
syphilitic proctitis are rare and usually seen in homosexually active men. Finally,
pseudomembranes, when present, suggest pseudomembranous colitis due to an
overgrowth of toxigenic Clostridium difficile. In summary, mucosal biopsy is
helpful in differentiating ASLC from IBD in most cases. Sometimes, it provides a clue to the specific infection.
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