Diagnosing eosinophilic colitis: histopathological pattern or nosological entity?

Reports of  "eosinophilic colitis"-raised colonic mucosal eosinophil density in patients with lower gastrointestinal symptoms-have increased markedly over the last fifteen years, though it remains a rarity. There is no consensus over its diagnosis and management, and uncertainty is compounded by the use of the same term to describe an idiopathic increase in colonic eosinophils and an eosinophilic inflammatory reaction to known aetiological agents such as parasites or drugs. In patients with histologically proven colonic eosinophilia, it is important to seek out underlying causes and careful clinicopathological correlation is advised. Because of the variability of eosinophil density in the normal colon, it is recommended that histological reports of colonic eosinophilia include a quantitative morphometric assessment of eosinophil density, preferably across several sites. Few reported cases of "eosinophilic colitis" meet these criteria. As no correlation has been shown between colonic eosinophil density and symptoms in older children or adults, it is suggested that treatment should be directed towards alleviation of symptoms and response to treatment assessed clinically rather than by histological estimates of intramucosal eosinophils.