Chronic Kidney Failure

The kidneys are made of thousands of tiny filtration units called nephrons. Once a nephron is destroyed by a disease, it cannot regenerate; this means that we all have a finite number of nephrons to last us our whole lives. Fortunately, we have many extra nephrons, so many extra that overall kidney function does not fall behind until we are down to about 1/6 of our original number of nephrons.

Nephrons can be destroyed quickly or slowly. Usually, by the time less than 1/6 of our original nephrons are left, whatever the inciting disease process was is long gone and there is no way to tell what happened. All we can do is make the kidney workload easier by make up for the kidney�s inadequate performance with medication or supplements. Hopefully, we can also slow the progression of the failure. Therapy is highly individual depending on which jobs the kidneys are having trouble doing.

If my pet is still making plenty of urine, how can there be kidney failure?

In chronic kidney failure, urine is usually produced in excessive quantities. What the kidneys are failing to do is conserve water (they fail to make concentrated urine). The body produces numerous toxins on a moment by moment basis. These toxins circulate to the kidneys where, dissolved in water, they are filtered out and urinated away. An efficient kidney can make highly-concentrated urine so that a large amount of toxin can be excreted in a relatively small amount of water.
When the kidneys fail over a long time period, they lose their ability to concentrate urine and more water is required to excrete the same amount of toxin. The animal will begin to drink more and more to provide the failing kidneys with enough water. Ultimately, the animal cannot drink enough and toxin levels begin to rise. Weight loss, listlessness, nausea, constipation, and poor appetite become noticeable. It is common for animals, especially cats, to have a long history of excessive water consumption when they finally come to the vet with one of the latter complaints.

Fluid Therapy- The Cornerstone of Treatment

Assuring optimal hydration is the single most important aspect of kidney failure treatment. The kidneys are made up of millions of small filtration units called nephrons. Blood is filtered by these nephrons such that waste chemicals and toxins are separated from desirable materials (such as proteins, sugars, electrolytes, etc.). The chemicals that the body needs are returned to the circulation, and the excesses and toxins are channeled into the urinary tract. The excesses and toxins must be kept dissolved in water for this process to work but the kidney, one of whose jobs it is to conserve water for the body, must be able to use the smallest amount of water possible to keep the toxins dissolved. This solution of waste toxins dissolved in water is urine. It is produced continuously by the kidneys, stored in the urinary bladder, and periodically dumped into the environment.

 

Graphic depiction of a nephron. Arteries are in red, veins in blue, and urinary tract in flesh color.

Over the time of one's life, nephrons are damaged and are no longer able to participate in the filtration process. They die from poor circulation, or they become clogged by toxin sludge, or they may simply wear out. Fortunately, we have many extra nephrons so losing some is not a big problem; that is, not a big problem until have lost about two/thirds of them. At this point the remaining nephrons will have trouble keeping up with the body's waste removal demands. Extra water is needed to remove the same amount of metabolic toxin. Since water cannot be conserved, the patient begins to drink excessively. Eventually, toxins build up and the patient feels sick.

This means that if the kidney disease is not detected until the patient is already feeling sick, less than one/third of the original number of nephrons are left. We need to maximize the efficiency of these remaining nephrons, and hopefully slow down their loss. We also need to get rid of enough toxins for the patient to feel good again.

Diuresis

Diuresis is the medical term for increased urine production. The patient is already doing this somewhat but the reality is that in order to get rid of more toxin, more urine must be produced. This is accomplished by giving the patient more fluid, either intravenously in the hospital or under the skin; this can be done in either the hospital or at home. The more fluid we put in, the more circulation there is through the remaining nephrons, and the more toxins can be excreted out.

Intravenous (IV) Fluid Therapy

Intravenous (IV) fluid therapy involves placement of an intravenous catheter in the leg or neck and a continuous drip of fluids is given directly into the bloodstream. The procedure is not painful or stressful, and after the catheter is placed the patient simply relaxes in a hospital cage, periodically receiving adjunctive oral or injectable medications.
After 2 or 3 days, lab tests are repeated to see what parameters have changed. Therapy is revised at that point to either continue IV fluids or discharge the patient with a new plan for home treatment.

IV fluid therapy offers many benefits to the kidney patient:

• Continuous hydration means continuous maximized nephron activity and the most efficient toxin removal.
• Rapid response to treatment (days).

Because hospitalization is needed for this treatment, a professional staff will be monitoring the patient's progress and can make rapid adjustments in adjunct therapy. 

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