Medical management of congenital portosystemic shunts in 27 dogs — a retrospective study. (svsvet.com)
A few clinical signs of portosystemic shunt include abnormal behavior after eating, pacing and aimless wandering, head pressed against the wall or constant rubbing of his head (the blood not being filtered causes ammonia buildup, which makes his head feel funny), and constant illnesses (since the liver is not filtering the blood, it causes toxicity in the blood, making your dog constantly ill). (animalbehaviorcollege.com)
Yorkies also have some joint problems, like trick knees (luxating patellas) and Legg - Calves - Perthes disease (poor circulation to the head of the femur), eye problems (like cataracts, eyelash diseases, and retinal dysplasia), weakness and collapse of the trachea, a liver disease called portosystemic shunt, and several other problems. (pethelpful.com)