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Hypertension (high blood pressure) is associated with about half of the cases of Cushing’s disease. It can cause blindness due to detachment of the sight receptors in the eyes (retina) and bleeding. Kidney problems are related to protein loss due to damage of the filtering system by the high blood pressure. Loss of the protein antithrombin III, which prevents clots, can cause thromboembolism (clots). Heart problems are associated with hypertrophy (thickening of the heart muscle) and failure due to the pumping of the heart against the increased pressure.
Glomerulopathy is damage to the filtering system of the kidney, causing protein loss. Up to 75% of dogs with Cushing’s have some protein loss, although most do not have severe complications. Proteins, especially albumin, are important in holding fluid within the blood vessels, and excessive loss can cause fluid accumulation in body cavities, underneath the skin, and the lungs. There are other proteins, such as antithrombin III, which are important in helping the body to prevent clotting within the blood vessels. Loss of this protein can predispose the animal to the development of thromboembolism (clots). A clot within an important organ, such as the lungs, can lead to the animal’s death. Ultimately, progressive glomerulopathy can lead to kidney failure, and predisposes the animal to hypertension, further damaging the kidneys. This vicious cycle can be the cause of the animal’s death.
Congestive heart failure is damage to the heart resulting in a decreased ability to pump blood forward through the blood vessels. Eventually, fluid accumulates in the lungs, chest & abdominal cavities, and can lead to the animal’s death. Excess fluid in the blood vessels due to too much fluid ingestion can lead to hypertension. Hypertension causes the heart to pump too hard, resulting in failure. Also, since many of these dogs are older animals, chronic valve disease may also be present, predisposing them to heart problems. This is a rare complication.
Pancreatitis is inflammation of the pancreas, the organ that produces enzymes to help digest food. With inflammation, the enzymes are excreted into the bloodstream and abdominal cavity instead of the gastrointestinal tract, resulting in a severe illness associated with vomiting, abdominal pain, peritonitis (inflammation of the abdominal cavity), and loss of protein into the abdominal cavity. If the disease is severe enough, the animal can have fatal complications. Controversy exists as to whether excess cortisol causes pancreatitis, since this complication is rare in dogs.
Thromboembolism is the formation of a clot within a blood vessel. If the clot forms within an important organ, the animal requires intensive care, and can have fatal complications. Cushing’s animals have thromboembolic disease due to glomerulopathy and antithrombin III loss, vascular stasis (blood pooling) due to an increase in blood cell numbers, damage to blood vessels due to hypertension, and an increase in clotting factors in the bloodstream.
Infections are common in Cushing’s patients, since excess cortisol suppresses the immune system. Urinary tract infections, skin infections, and rarely systemic infections (sepsis) can occur. Since cortisol also decreases inflammation, often there are no clinical signs or elevations in white blood cells in the area of infection.
Decreased wound healing and slowed hair regrowth also occur in Cushing’s patients, since the excess cortisol inhibits the normal healing and growth processes. For this reason, surgery in adrenal tumors is often postponed until the cortisol levels can be controlled, usually with ketoconazole.
