Pathology of emphysematous reticulitis in cattle: report of two cases and comparative overview of similar or identical conditions

Inflammatory forestomach disorders other than those of viral, bacterial, mycotic, parasitic, chemical, or plant poisoning origin are uncommon in the bovine species. Spontaneous focal emphysematous lesions were grossly identified in the reticulum—the second part of the forestomach—of two adult Holstein-Friesian cattle (one 2-year-old steer, the other 3-year-old dairy cow). Both cattle, which appeared to be clinically normal without evidence of apparent forestomach dysfunction or other significant abnormalities on physical examination, were slaughtered conventionally for human consumption. At postmortem inspection of these two cattle, the reticulum wall showed focal spongy areas due to the occurrence of numerous minute gas bubbles (<1.0 mm in diameter). On histopathology, this emphysematous lesion was characterized by the presence of multicystic emphysematous lymphangiectasis in the submucosa. Affected lymphatics were prominently inflamed, being infiltrated to a significant degree with eosinophils and granulomas consisting of macrophages and multinucleated foreign-body giant cells in the lumen. Submucosal connective tissues surrounding the areas of lesional lymphatics exhibited varying degrees of cellular infiltrates, including eosinophils, mast cells, macrophages, plasma cells, and lymphocytes. Additionally, edema, hemorrhage, fibrin-clot formation, or collagen fiber deposition was observed throughout the lesional submucosa. There was no evidence of bacterial, mycotic, protozoal, or parasitic infection elsewhere in the lesions. Although the precise cause and pathogenesis of this emphysematous reticulitis remain unknown, there was the likelihood that a hypersensitivity reaction might have played a certain role in the development and progression of the lesions. Histopathological features of the reticulum were consistent in many respects with those documented previously in a bovine condition referred to as emphysematous eosinophilic lymphangitis in the ruminal submucosa. From the viewpoint of comparative pathology, this article provides a brief overview of similar or identical conditions involving other organs, which have previously been described in human beings and animals.