Acetaminophen (Tylenol) [ In Poisons and Overdoses ]
Acetaminophen (Tylenol) can cause liver damage in dogs. The toxic dose is 150 mg/kg.

Addison's disease [ In Endocrine Diseases ]
Addison's disease, also known as hypoadrenocorticism, is a reduction of production of glucocorticoids and mineralocorticoids by the adrenal glands. It is most commonly caused by destruction of adrenal tissue, probably by autoimmune disease. Signs include increased drinking and urination, vomiting, diarrhea, collapse, and weight loss. Hyperkalemia can develop and cause severe bradycardia. Treatment is with supplementation of mineralocorticoids in daily pills or a monthly injection. Glucocorticoids are usually supplemented with oral prednisone.

Anal fistulae [ In Gastrointestinal Diseases ]
Anal fistulae, known as perianal fistulae in dogs, are most common in German Shepherd Dogs. They are characterized by draining tracts in the skin around the anus. The cause is unknown. Surgical treatment is common, but recently use of cyclosporine in combination with ketoconazole has been shown to be effective.

Anal gland problems [ In Miscellaneous ]
Anal gland problems are a very common issue with dogs. Disease of the anal glands or anal sacs may include impaction, infection, or abscessation. The dog will periodically discharge a fishy-smelling substance from its anus when they get too full. These glands are normally expressed when the dog defecates.

Anal sac adenocarcinoma [ In Cancers ]
Anal sac adenocarcinoma is an uncommon and aggressive malignant tumor found in dogs that arises from the tissue of anal sac.

Antifreeze [ In Poisons and Overdoses ]
Antifreeze is very dangerous to dogs and causes central nervous system depression and acute renal failure. Treatment needs to be within eight hours of ingestion to be successful.

Aortic stenosis [ In Cardioascular and Circulatory ]
Aortic stenosis is a congenital disease in dogs characterized by left ventricular outflow tract obstruction. It is inherited in Newfoundlands, and also found in Golden Retrievers, Rottweilers, Boxers, Bulldogs, German Shepherd Dogs, and Samoyeds. Signs include fainting and exercise intolerance.

Aspergillosis [ In Fungal Infections ]
Aspergillosis is a fungal disease that in dogs is caused primarily by Aspergillus fumigatus. Infection is usually in the nasal cavity. Typical signs in dogs include sneezing, nasal discharge, bleeding from the nose, and ulcerations of the nose.

Asteroid hyalosis [ In Eyes ]
Asteroid hyalosis is a degenerative condition of the eye involving small white opacities in the vitreous humor. The cause is unknown.

Atopy [ In Skin ]
Atopy is an allergy to a substance with which the dog is not necessarily in direct contact. It is a type I hypersensitivity to a substance that is inhaled or absorbed through the skin. Up to 10 percent of dogs are affected. It is common in dogs, especially seen in breeds such as Labrador Retrievers, Golden Retrievers, and Shih Tzus. The most common symptom is itching. Affected areas include the underside, the face, the feet, and the ears.