An endoscopic and histologic perspective of diagnosis: when, where, and what to do.

Colon biopsies are critical in helping to diagnose diarrhea, to distinguish different forms of colitis, to determine the extent of disease, and to determine if neoplasia has arisen in the setting of chronic colitis. Colon biopsies in some instances can be definitive, but this usually requires the appropriate clinical scenario. For instance, to appreciate that segmental granulomatous colitis is CD and not the much rarer colonic sarcoidosis requires ancillary clinical information. Often colon biopsies may definitively reveal an abnormality, but the findings may be non-specific in regard to a definitive diagnosis. Thus, to utilize colon biopsies most appropriately in patient management usually requires frequent clinician-pathologist interaction, often repeat endoscopy with biopsies at a different time, and the assessment of any prior biopsies or resections. Once a patient has a firm diagnosis of CD he/she rarely converts to a disease that is indistinguishable from UC, and typically continue to behave like CD. Conversely, it is not too uncommon for patients with UC to develop features that strongly suggest that CD is the real underlying disease. These patients also tend to behave like those with CD. The ileum should be intubated whenever possible in cases of undiagnosed diarrhea and in cases of colitis to help distinguish if CD might be present. Gastric biopsies may reveal a pattern of focally active gastritis and this may serve as a clue for CD when the diagnosis is unknown or in doubt. [ABSTRACT FROM AUTHOR]