Hypertension refers to persistently high blood pressure. A dog’s blood pressure relates to the volume of blood pumped out of its heart and the degree of resistance, or elasticity, of its blood vessels. Blood pressure is usually highest when the heart contracts and lowest when it relaxes and fills. Hypertension can be caused by many things, including genetics, hyperthyroidism, Cushing’s Disease, diabetes, endocrine abnormalities, administration of certain drugs, stress, pain and liver, kidney or lung disease. High blood pressure is difficult to detect in dogs, because many of them don’t show any signs of distress when their blood pressure is elevated. However, if it remains elevated for a long time, the dog probably will experience some degree of pain or discomfort. Other possible symptoms include acute onset of blindness, bleeding inside the eyeballs, dilated pupils, detached retina, abnormal eye movements, bloody urine, nose bleeds and general disorientation. Some hypertensive dogs develop seizures.