RESUMEN
In this report, the late clinical, necropsy, and histopathological findings of idiopathic gastric stasis in an ostrich are described, with special attention to the proventriculus. An ostrich with clinical signs of gastric stasis was brought to our clinic in a state of impending death that could not be reversed with emergency medical care. At necropsy, the koilin layer of the gizzard was uneven without ulcerations. The proventriculus was distended with food items without impaction and mucosal lesions. None of the most typical aetiological factors including foreign objects, Macrorhabdus ornithogaster and parasitic infection with Libyostrongylus douglassii was present. Histologically, the proventriculus was characterised by hyperplastic mucosa with luminal buds and necrotic cells in the lumen. Immunochemistry for proliferating cell nuclear antigen (PCNA) revealed a high rate of proliferation in epithelial cells of the glandular and mucosal lining in the proventriculus neighbouring the affected gizzard: approximately 88.6% of the cells were immunoreactive as compared to 34.4% of the cells in control ostriches used for comparison. In conclusion, in the absence of gizzard contraction, the mucosal lining of the proventriculus is hyperplastic with a high rate of proliferation that may help compensate the distension due to the accumulation of food items.