Kidney amyloidosis is an uncommon disorder of protein metabolism in which a protein called amyloid is abnormally deposited in the kidneys, causing excessive protein loss in the urine.
Among the domestic animals, it is most common in dogs, and seems to be a hereditary disorder in shar-pei dogs. Chronic inflammatory diseases can predispose animals to the development of kidney amyloidosis; however, only a small percentage of animals with chronic inflammatory conditions develop amyloidosis, thus, other factors must also be important in the development of amyloidosis. These other factors are poorly understood. Most dogs with amyloidosis do not have discernible inflammatory or infectious conditions at the time of diagnosis. However, various diseases have been observed in some dogs with amyloidosis, such as systemic fungal diseases, chronic bacterial infections, heartworm diseases, and cancer.
Most dogs with kidney amyloidosis are old at the time they are diagnosed with the disease. The average age is 9 years in dogs. The hereditary form tends to strike earlier; affected shar-peis are 4 years old on average at the time of death or euthanasia from the disease. Beagles, collies, pointers, and Walker hounds may be at increased risk, while German shepherds
and mixed breed dogs are less prone to the disorder. Both sexes are affected, although a slight predilection for females may be present.
In dogs, amyloid deposits in the kidneys lead to eventual kidney failure. Signs of kidney failure include anorexia, lethargy, and weight loss. Excessive water consumption and urination is another common sign of kidney failure. Occasional vomiting is also seen.
Kidney amyloidosis causes excessive protein loss in the urine. One of the proteins lost in the urine is a protein responsible for preventing the blood from clotting. As a result, affected dogs are more susceptible to formation of blood clots. These clots tend to lodge in the lungs, causing clinical signs that may not be obvious, ranging from labored breathing to major respiratory distress.
Excessive urinary loss of a protein called albumin may lead to ascites, which is an accumulation of fluid in the abdomen. It may also lead to edema, which is a swelling of the limbs and/or face. Ascites and edema are relatively uncommon occurrences in dogs with kidney amyloidosis.