Chronic renal failure

General Comments and Information: (this is not specific to your pet but is for background information concerning possible problems or diagnoses being considered):

by Atlantic Veterinary Internal Medicine Group

Chronic renal failure (CRF) is, unfortunately, a leading cause of illness in dogs and cats. This disease can be due to long-term inflammation from unknown causes or from specific diseases. The most common cause is chronic interstitial nephritis (CIN) and this has no identified cause. It can occur at any age but is more common after 10 years.

Other causes or associated conditions include chronic viral disease, high blood pressure, blood clots (emboli), cancer, high thyroid hormone levels, severe shock, chronic inflammation, abnormal protein deposition (amyloid), and dehydration. This failure (insufficiency) of the kidneys results in poor ability to concentrate toxic waste products form the blood/ plasma into the urine and to conserve/eliminate water (concentrate the urine, or dilute the urine). CRF commonly results in increased risk of urinary tract infections (UTI) and vigilance for these is needed by periodic testing of urine.

Many problems occur when there is kidney dysfunction. These include increased thirst and urination, loss of smell, poor appetite, high blood pressure, anemia, lethargy weight loss, protein loss in urine, problems of calcium and phosphorous metabolism, low serum potassium (muscle problems), platelet dysfunction (bleeding), gastritis and ulcers or vomiting, and occasionally brain dysfunction (uremic encephalopathy).

The classification of CRF is often denoted as being compensated or uncompensated. Crises are present when the pet is diagnosed as being uncompensated renal failure. Standard blood tests that are used to look for kidney dysfunction need to be interpreted with respect to other illnesses/conditions, dehydration, and urine analysis (UA). These tests (creatinine and BUN, phosphorous) do not increase until 75% loss of kidney function has already occurred with CRF.

Therefore even mild elevations are a concern. Cats and dogs that are experiencing de/un- compensation of CRF are usually treated with intravenous (IV) fluids or subcutaneous fluids (SQ fluids), monitoring of blood counts and body salts (especially potassium levels).

There are some cases where use of an endoscopically placed convenient stomach tube can be easier that subcutaneous fluids. Other medications are supportive and can include glucose (in IV fluids), vitamins, anabolic steroids, phosphorous binding medications, blood pressure drugs, antacids such as Pepcid, blood production stimulants and others as warranted. The prognosis for CRF is variable. It depends upon age of onset, current condition of the patient, concurrent clinical problems present, and the individual pet’s ability to tolerate a less that ideal kidney function. The latter is the hardest to predict.

Some pets survive years doing well with a good quality of life. Others do poorly within weeks or days. Only an attempt at treatment will answer the question. The most consistency agreed upon treatments are fluids and diet.

A diet designed for kidney disease patients is moderately restricted in protein, low in phosphorous, and modestly restricted in salt (NaCl). Prescription diets can be discussed and home recipes provided if your pet does not eat the prescribed diets.

Renal transplantation is done in cats that do not have any other illness. But it is not done commonly. Survival at 1 year is 80 but survival at two years is almost zero. Hemodialysis is not a viable option in chronic renal failure cases except for large dogs with good veins. It, like transplantation, requires thousands of dollars, in cost (and does not reverse the kidney disease).

Proteinuria is a term that describes loss of proteins from the serum via the kidneys into the urine. The proteins most affected are smaller molecular size proteins such as albumin and some of the proteins that deal with prevention of blood clots and procoagulation of blood. Protein loss in the urine, in the absence of red blood or bacterial infection, results from injury to the filtering apparati of the kidney nephrons. These are called glomeruli. Each glomeruli is attached to a kidney tubule. The whole unit is microscopic is size called a “nephron”. There are thousands of nephrons in each kidney. The glomerole acts as the initial filter of blood and the tubule then adjusts the excretion of wastes and water balance. If the glomeruli are damaged or diseased, then often the tubule will also die. Animals with proteinuria may develop low serum protein (low albumin), increased risk of blood clots or hemorrhage, swelling of limbs (edema), high blood pressure. It is also possible as kidney tubules subsequently fail that the pet can develop more typical signs of kidney failure (increased waste products in the blood, e.g., BUN and creatinine and phosphorous). Protein losing nephropathy (PLN) is another way of describing disorders that result in proteinuria. Common diseases that cause protienuria include glomerulonephritis, congenital renal dysplasia, systemic lupus erythematosus, chronic Lyme disease, and other long-term inflammation or infection conditions (e.g., heartworms, brucellosis, disospondylitis). The prognosis for protein losing nephropathies is always guarded unless an underlying primary condition, that is causing injury to the glomeruli secondarily, can be found. Treatments often rely upon diet, aspirin blood pressure medications and sometimes conticosteriods in cautious use.

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