Gastric intramural hematoma and hemoperitoneum in a captive northern fur seal

A 18-yr-old adult male northern fur seal (Callorhinus ursinus) was found de ad in its outdoor pool in November 1995. The animal was maintained at Mysti c Aquarium (Mystic, Connecticut, USA) from March 1980 to November 1995. Cro ss necropsy findings included hemoperitoneum and locally extensive gastric intramural hemorrhage that involved the posterior fundic, antral, and pylor ic regions and extended into the duodenum. The gastric mural thickening gro ssly resembled hemangioma, and the gastric serosa was ruptured at the site of maximal mural expansion. In histologic sections of the stomach, a cribif orm network of fibrin, which encompassed numerous variably-sized aggregates of closely packed erythrocytes, markedly expanded the submucosa. No vascul ar endothelium was identified in serial histologic sections of the expanded gastric submucosa stained with hematoxylin and eosin or immunohistochemica lly with antibodies to vimentin and Factor VIII-related antigen. establishi ng an absence of hemangioma. Carstairs' and Weigert's histochemical stains confirmed that the framework expanding the submucosa was fibrin. Although t he appearance of the gastric wall resembled hemangioma, a population of neo plastic endothelial cells was not identified within the submucosal expansio n of hemorrhage and fibrin, and microscopic evidence was most consistent wi th the diagnosis of gastric intramural hematoma. This lesion is a rare path ologic event that has not been reported in marine mammals, but one that sho uld be included in diagnostic considerations of hemoperitoneum and gastric mural expansion.