• When the kidneys fail, a horse's body stops functioning correctly.horse image by Oleg Tarasov from Fotolia.com
  
  Kidney failure occurs when the kidneys lose their functionality and fail at their filtration responsibilities. Kidneys are in charge of filtering the blood to send waste and extra fluid to the bladder, and they are an important part of a horse's urinary tract. When they fail, due to genetics, age or damage, the horse exhibits some specific symptoms.
  
  

Increased Thirst and Urination

• According to the website EquiSearch, a horse's kidneys must filter 10 gallons of blood twice an hour to efficiently clean out toxins and excess fluid. Their breakdown leads to a buildup of toxins, which in turn leads to the horse's body seeking other methods of filtration. Increased hydration is a natural impulse. A horse becomes increasingly thirsty as its body seeks to dilute the blood and the toxins that flow through it. This increased thirst leads to increased urination and diarrhea. Horses with kidney disease begin to urinate several times an hour.
  
  

Blood in Urine

• A standard symptom of kidney damage in animals is blood in the urine. The renal artery delivers a constant supply of blood to the kidneys for filtration, but as the kidneys break down, this filtration system fails. Instead of filtering blood and passing only excess water to the bladder, kidneys begin to funnel the blood itself into the urinary tract. This leads to pinkish urine, and can lead to the horse passing pure blood.
  
  

Physical Appearance and Behavior

• As kidney disease progresses and toxins build up, the horse begins to show some physical signs of illness. Its coat may become dull and patchy, while the horse will probably become listless and lethargic. Kidney disease sometimes acts as an appetite suppressant, according to the website EquiSearch, so horses may stop eating. This results in weight loss and further lack of energy. Another possible symptom is inflamed gums.