Addison's disease, also known as hypoadrenocorticism, and liver shunt are two vastly different conditions. You're unlikely to confuse the symptoms of one with the other in your pet, with one exception: Both disorders can cause seizures. Without treatment, both conditions can prove fatal.
Addison's disease results when a dog's adrenal glands don't produce enough cortisol, a hormone that aids in handling stress. Symptoms include appetite loss, lethargy, seizure, vomiting and diarrhea, excessive drinking and urination, hair loss and blood in the stool. Many dogs start showing symptoms after a stressful situation, such as a move or stay in a boarding facility. Dogs experiencing a sudden "Addisonian crisis" might collapse and require emergency veterinary treatment to survive.
Most dogs with liver shunt are born with it, although a small percentage later develop shunt because of a liver disease, such as cirrhosis. In utero, the mother dog's liver does the work for her fetuses. Once the puppies are born, the shunts rerouting blood to the mother's liver should close and the puppies' livers kicking in. In some dogs, that doesn't occur. Blood isn't filtered by their livers because of the shunts, so toxins build up in the dog's system. Since the condition is congenital, dogs show symptoms at a young age. They don't grow properly and might display behavioral oddities. These include circling, seizures, pressing their heads into solid objects and seeming generally "out of it." Many puppies with liver shunt become blind. Without treatment, toxins circulating throughout their bodies eventually cause organ failure and the dogs die.
Addison's disease primarily affects young to middle-aged dog, with females more likely to come down with the condition than males. While any dog might suffer from hypoadrenocorticism, bearded collies, Rottweilers, West Highland white terriers and standard poodles appear to have a genetic predisposition. Liver shunt primarily affects small breeds; the Yorkshire terrier is far and away the most common breed born with a shunt. Other breeds prone to congenital liver shunt include the toy and miniature poodle, the Maltese, the cocker spaniel, the Lhasa apso, the Shih Tzu, the dachshund and the cairn terrier. Larger breeds prone to liver shunt include the Irish wolfhound and the Labrador retriever.
Addison's Disease Treatment
Dogs experiencing Addisonian crisis require intravenous fluids and steroids. Dogs diagnosed with the disease either receive fludrocortisone acetate in pill form twice daily or a monthly injection of desoxycorticosterone pivalate.
Liver Shunt Treatment
Depending on test results, your vet might start out treating your dog medically, with dietary changes and administration of lactulose, a sugar that makes the intestines less likely to produce toxic bacteria. While medical management does help some dogs, most require surgery in order to live a relatively normal life span. Surgery involves placement of a metal ring "lined by a material that slowly expands and causes shunt narrowing over three to 14 days postoperatively," according to the American Kennel Club Canine Health Foundation.