Kidney Filtration Problems in Dogs

Nephrotic syndrome is the abnormal presence of proteins in both blood and urine of a dog. This condition usually occurs secondary to either glomerulonephritis (GN) (immune-mediated inflammation of the portion of the kidney called the glomerulus) or amyloidosis (accumulation of amaloids {proteins} in body). Glamerulus is a cluster of nerve endings or blood vessels, esp. the capillaries, around the end of kidney tubule where waste products are filtered. These glameruli are made up of filtering cells known as podocytes. The nephrotic syndrome disorder is characterized by having pores in the podocytes that are large enough to permit proteins (proteinuria) to pass into the urine. This results in hypoalbuminemia due to loss of protein albumin (necessary for regulating blood pressure and keeping blood in vessels) and loss of antithrombin III, another protein that is essential in preventing clot formation, from blood to the urine. When the daily loss of proteins exceeds 3.5 gms, blood pressure falls, less blood stays in the blood vessels, and consequently, the kidneys act to conserve sodium in the body. This causes swelling of the limbs, hypertension and fluid accumulation in the abdominal cavity.

Signs of hypothyroidism may also be evident in the affected dogs due to loss of vital thyroid proteins. Decreased cholestrol break-down rate and muscle wasting are also indicative of nephrotic syndrome. An increase in the production of proteins and lipids in the liver causes further elevation in cholesterol (hypercholesterolemia), resulting in thickening of arteries — a condition known as arteriosclerosis. Loss of antithrombin III causes blood clotting in blood vessels which may result in paralysis and/or stroke. 

Accumulation of urea nitrogen and creatinine in the bloodstream can also occur as a result of progressive glomerular disease which can lead to kidney failure.

Middle-age to old dogs are more affected by this relatively common condition. The affected dogs show signs which include

Swelling of the limbs

Abdominal enlargement due to fluid accumulation in the abdomen

Retinal: hemorrhage or detachment due to high blood pressure

Swelling of the optic nerve (at the back of the eye) due to high blood pressure

Heart rhythm disturbances due to enlargement of the left ventricle of the heart

Difficulty breathing

Bluish-purple skin color

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