Microaggregate of immunostained macrophages in noninflamed gastroduodenal mucosa: a new useful histological marker for differentiating Crohn's colitis from ulcerative colitis

OBJECTIVE: In 10% of cases it may be difficult to differentiate Crohn's colitis from ulcerative colitis. Distinguishing the two conditions is important because they are distinct entities with different therapeutic implications. Noncaseating granulomas are usually considered diagnostic of Crohn's disease. We previously reported that the presence of a microaggregate of immunostained macrophages within the noninflamed gastroduodenal mucosa was a characteristic finding of Crohn's disease. The aim of this study was to determine whether a microaggregate of immunostained macrophages can be a reliable marker for differentiating Crohn's colitis from ulcerative colitis. METHODS: We investigated the presence of microaggregates of immunostained macrophages and epithelioid cell granulomas in biopsy specimens taken from the noninflamed gastroduodenal mucosa of 22 known Crohn's colitis patients and 23 established ulcerative colitis patients. The incidence of microaggregates and granulomas was compared between these two groups. RESULTS: Microaggregates and granulomas were detected only in the Crohn's colitis patients. In addition, the presence of microaggregates was more frequent than that of granulomas in Crohn's colitis patients (54.5% and 18.2%, respectively, 95% confidence interval for the difference: 10.0-62.7%). CONCLUSION: Detecting a microaggregate of immunostained macrophages in a biopsy specimen taken from noninflamed gastroduodenal mucosa seems to be a useful method for differentiating Crohn's colitis from ulcerative colitis.