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RENAL FAILURE
Renal or kidney failure is a disease complex where the kidneys cannot concentrate or dilute urine or filter enough blood to remove the toxins the body normally makes each day.
When over 2/3 of the kidney tissue does not function the animal can no longer concentrate or dilute urine. This inability leads to increased urine output. The body must replace this lost water so you may see your pet drinking more water than normal.
When over ¾ of the kidney tissue is not functioning we will start to see changes on lab work showing a build up of toxins in the body. More specifically an elevated BUN, Creatine, and Phosphorus are noted.
Bun (blood urea nitrogen) is a protein waste product that is made by the liver and eliminated by the kidney. The body will not store protein so it must be disposed of daily. Excess protein comes in from an inappropriate diet, bleeding into the gastrointestinal tract and/or muscle catabolism. As protein is broken down it is converted to ammonia. Ammonia is a strong base and can't be allowed to circulate in the blood so the liver converts it to urea. The urea is eliminated by the kidney through filtration and is actively reabsorbed if the urine flow is too slow. As the kidney fails urea (BUN) and ammonia levels start to rise in the body causing sickness and further kidney damage.
Creatine is a muscle tissue breakdown product that is produced at a constant rate. The kidney eliminates it from the body by filtration. If the creatine level is elevated, the amount of blood being filtered is decreased.
Phosphorus enters through food and is under complex hormonal control along with calcium levels. As the kidney fail less phosphorus is filtered, less is reabsorbed but more is mobilized from the bones. Phosphorous levels rise in the blood, causing calcium levels to fall. Low calcium causes more bone and intestinal absorption of phosphorous and another vicious cycle has begun.
Normally a low calcium concentration would lead to more vitamin D synthesis. Vitamin D would increase the amount of calcium being absorbed from the diet and decrease the amount being absorbed from the bone. This would help to slow down the rate of phosphorus elevation and stop the cycle. Unfortunately, vitamin D is made by the kidney. When the kidneys have failed they cannot make enough vitamin D to stop the spiral.
As the above cycles continue, toxins build up leading to poor appetite, decreased water consumption and increase in the bodies own proteins being broken down. These changes further increase toxin levels as all of the problems continue. Eventually bleeding ulcers, vomiting, diarrhea, coma and death ensue.
Initial treatment involves high volumes of fluids to flush the wastes out. The speed and success off this treatment is dependent upon how much kidney tissue is really left. As the BUN, Creatine and Phosphorous levels start to fall and the animal starts to eat, the amount of fluids will be reduced to see if the body will hold itself in “remission”. Again this is dependent upon how much functioning kidney tissue is present. Some animals will require regular fluid supplements at home or in our clinic because they cannot drink enough water to keep the toxin levels under control.
As recovery proceeds our goal is to send the patient home on a diet that is low in protein, phosphorous, salt and has an above normal level of vitamin D3. We currently recommend Hill's K/D or Hill's U/D. Please feed ONLY this diet. No treats or table food. If your pet refuses to eat this food, we will provide a recipe for a homemade diet that you can prepare.
Renal failure tends to be a life long progressive disease. We will work together to follow changes in fluid needs, diet and medication. However, these medicines and diets have been proven to prolong the quantity and quality of life for your pet.
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