Equestrian Days - Kidney Failure in Horses

From Your First Horse to Your First Foal

In those relatively rare instances when kidney function is disrupted, waste products accumulate in the blood and eventually poison the system. Yet a horse with the usual subacute or chronic kidney dysfunction usually seems more "off" than ill. He may be a little lethargic or depressed. He may have a little less appetite and his performance level may not be up to par. His coat may lose some of its usual luster. Unfortunately, these signs appear only in the later stages of most kidney disease, and can easily be attributed to another illnesses. Taken together, however, poor performance, lethargy or depression and a rough coat earn a careful investigation for kidney disease.

Other signs of kidney dysfunction include:

Abnormal urination. A healthy, resting horse consumes an average of 5 to 7 gallons of water a day, and produces anywhere from 1 to 3 gallons of urine. In contrast, a horse with kidney disease may pass a flood of urine no matter how much liquid he consumes. He may drink no more water than usual or he may seem unable to quench his thirst. Whatever the case, his damaged kidneys cannot conserve water and they may purge the body of fluids during times of distress. Instinctively, the horse will usually drink more water to help maintain an adequate level of hydration or to flush out accumulating waste products. His urine may be strong smelling or discolored due to a concentration of waste products, or it may be as pale as light beer.
Weight loss. An increase of wastes in the blood can have an appetite-suppressant effect, so the horse eats less. The wastes accumulate because the kidney cannot properly retrieve essentials or secrete excess chemicals.
Excessive dental tartar or gingivitis--an inflammation of the gums--can be a sign of that excess urea and ammonia circulating in the blood.

If these signs always followed a distinct pattern, perhaps veterinarians would find it easier to diagnose equine kidney disease. But there is no textbook progression that points to kidney damage, and one sign can crop up long before others appear.

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"Chronic renal failure has an insidious onset and usually shows up as chronic weight loss," says Harold Schott, II, DVM, PhD, a specialist in equine kidney function at the University of Michigan. "That's the number-one complaint, but weight loss could mean anything. Sometimes the owner will complain of increased water consumption and might not recognize that the stall is wetter than usual. It's easier to detect more urine with smaller animals." Schott adds that a horse with kidney disease might also begin to "feel punky" as more and more waste products accumulate in the bloodstream.

Veterinarians categorize kidney disease based on the length of time the signs of illness have persisted and the severity of the disorder. Acute renal failure is a temporary and sometimes curable form of kidney disease. Its onset is triggered by a sudden cessation of waste excretion, accompanied by electrolyte and water imbalance. According to Schott, acute renal failure is most often caused by a loss of blood volume due to colic, diarrhea, hemorrhage or severe dehydration. Ingested toxins and antibiotics administered to a dehydrated horse also may contribute to the onset of the condition.

In contrast, chronic renal failure affects the kidneys progressively, gradually destroying more and more of the cells needed to regulate fluids and excrete wastes. Chronic renal failure can follow acute renal failure if a case of acute renal failure is not treated. Chronic renal failure also can result from toxic poisoning, or glomerulonephritis--inflammation of the capillary tufts at the top of each nephron.