RESUMEN
A 2-year-old Miniature Dachshund was admitted to the hospital because of fever, frequent vomiting, and watery diarrhea. An intra-abdominal mass and a gastric ulcer were detected. At laparotomy, the omentum was yellow but not icteric, irregularly thickened, and fragile, and a large mass involving the root of the mesentery and the gastrosplenic ligament was found. The histopathologic diagnosis was steatitis, and the dog was treated with prednisolone and cyclosporine for 2.5 years. After 1.5 years, the abdominal mass was not detectable. The dog died suddenly from perforation of the small intestine caused by a foreign body. Necropsy revealed severe adhesions between portions of the small intestine, and cicatrization of the mesentery. Cause of the mesenteric and omental steatitis was not apparent.