Case records from the small animal necropsy service of the University of Pennsylvania (Philadelphia, PA) from January 1981 through August 1990 were searched for reports of animals with grossly visible portal vein thrombi. Eleven dogs identified from their case materials as having portal vein thrombosis were used for this study. The age of the dogs ranged from 2 to 13 years, and there were five spayed females and six males-four intact and two castrated. Seven breeds were represented (Lhasa Apso, German Wire haired Pointer, Shetland Sheepdog, Dalmatian, Irish Wolfhound, Old English Sheepdog, and Siberian Husky), and the remaining four cases were identified as mixed breeds. The weight of the dogs ranged from 7.7 to 50 kg, and most of them were considered overweight. Dogs with microthrombi and tumor emboli in the portal vein were excluded. No age, sex, or breed predisposition was found. Thrombi were also detected in the pulmonary arteries in five of the dogs and both the pulmonary arteries and aorta in one dog. The portal thrombi extended into the mesenteric veins in three dogs, resulting in infarction of the jejunum. One of these dogs and two other dogs had chronic occlusion of the portal vein, with the formation of secondary portosystemic shunts. Conditions also present in dogs with portal vein thrombi included pancreatic necrosis (four dogs), peritonitis (two dogs), distant neoplasia (three dogs), and therapy with steroids (ten dogs).
