The circulatory system is comprised of the heart and blood vessels. Blood circulates throughout the body inside a connected series of blood vessels. Beginning in the right side of the heart, blood is pumped into the lungs, where it picks up oxygen and then returns through the left side of the heart into aorta. From the aorta the oxygen-rich blood enters arteries, which eventually branch into smaller arterioles and finally into even smaller capillaries which supply tissues with oxygen. The oxygen-depleted blood then returns to the heart for recirculation through tiny venules and then thicker veins, passing through the liver and kidneys along the way, where carbon dioxide and other waste products are removed. Circulatory disorders in general refer to defects in circulation of blood in the brain, liver, lungs, kidneys and abdominal organs. There are many diseases and disorders associated with circulatory problems, which exist when oxygenated blood canot make the complete circut of the body without restriction. There are many reasons why blood flow may be inhibited: clots, injuries, tumors, and inflammatory diseases of the blood vessels; congenital heart and liver defects, and various heart diseases and disorders.
Disorders of the Blood Vessels
Atherosclerosis (hardening of the vessels due to formation of atherosclerotic plaques).Incidence of atherosclerosis in dogs and cats is far less common than in humans, and is usually results from other diseases, namely hypothyroidism, diabetes mellitus, hypercholesterolemia or hypertriglyceridemia. Hypertension is associated with Cushing syndrome). Chronic kidney disease can be a cause, as well as a consequence of hypertension, which constitutes a major risk factor for the progression of kidney disease and vascular complications.4 Arterial thromboembolic disease and pulmonary thromboembolism have been associated with many conditions, including protein-losing nephropathy, Cushing syndrome, tumors, chronic nephritis, heartworm disease, hypothyroidism, bloat, pancreatitis, arteritis (inflammation of the arteries), and a number of cardiovascular diseases.5
Circulatory Disorders of the Liver
Circulatory disorders of the liver in dogs and cats can be categorized as congenital portosystemic shunts, disorders associated with outflow disturbances resulting in passive congestion of the liver, and disorders associated with portal hypertension. Chronic passive congestion of the liver is almost always the consequence of heart failure. Portal hypertension is the abnormal persistent increase in pressure in the portal venous system. Consequently, it is often accompanied by acites and acquired portosystemic shunting via collateral vessels. Portal hypertension is regularly seen in dogs but rare in cats.1 In the dog, it is usually the result of advanced liver disease. Disorders associated with portal hypertension include portal vein obstruction (thrombosis induced by local inflammatory processes, parasitic infestation, and tumors); primary hypoplasia of the portal vein, and Thrombophlebitis of the portal vein.
- WSAVA Standards for Clinical and Histological Diagnosis of Canine and Feline Liver Disease. World Small Animal Veterinary Association. Liver Standardization Group, Jan Rothuizen.
- M. Donald McGavin, James F. Zachary. Pathologic Basis of Veterinary Disease
- The New Harvard Guide to Women's Health. Karen J. Carlson, M. D., Stephanie A. Eisenstat, Terra Diane Ziporyn
- Renal oxidative stress, oxygenation, and hypertension
- Cardiovascular Disease in Small Animal Medicine. Wendy A. Ware