An unusual portosystemic shunt in a dog.

An unusual portosystemic shunt was diagnosed in a 4-month-old male Miniature Poodle examined because of stunted growth and episodes of dementia characterized by hysteria, ataxia, and staggering. Operative splenoportography revealed a portosystemic shunt. Exploratory surgery to identify and correct the shunt was attempted. Evidence of any portal circulation was not detected, and the dog was euthanatized. The possible embryologic basis for this vascular anomaly is discussed.