The spectrum of eosinophilic infiltration of the cecum and its relationship to other disorders of multiple granulomas and arteritis in Sprague-Dawley rat.

Spontaneous multiple granulomas were present in the animal under the SPF condition and without chemical treatment, in a 19-week-old male Sprague-Dawley control-group rat. Here we describe multiple granulomas and prominent diffuse infiltration by eosinophils in the cecal submucosa, and arteritis in the mesenteric arteries. The multiple granulomas were characterized by central eosinophilic degeneration or necrosis, prominent eosinophils, many multi-nucleated giant cells and abundant fibroblasts. They were restricted to the cecal submucosa. The mesenteric arteritis consisted of fibrinoid necrosis of the intima and media, intense inflammatory cell infiltration and fibrosis in the arterial wall. An affected artery in the cecum was continuous with the mesenteric artery. The foregoing tissue changes in this rat correlate with the high absolute blood eosinophil count found in this animal.