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MANAGEMENT
The implications of excessive urination
Q: My 11-year-old Quarter Horse gelding has always been healthy, but lately I’ve noticed that he seems to be urinating more than usual. I don’t actually see him emptying his bladder more often, but I do find that I’m removing more wet bedding from his stall than normal. Is this something to be concerned about? He seems otherwise fine.
Name withheld by request
A: Excess urination is called polyuria (PU). For a horse with PU to maintain a normal hydration state, he must also have polydipsia (PD), which is increased drinking. PU/PD can be a consequence of diet, a behavior problem or a sign of disease.
The kidneys filter waste products from the blood and eliminate these wastes in urine. They also regulate the volume of water in the body by producing urine that is either more concentrated than blood (deep yellow urine) or more dilute than blood (a clear urine that looks like water). More than 99 percent of the water filtered from blood by the kidneys is reabsorbed in the kidney tubules, allowing excretion of nitrogenous waste products at a 100-fold-or-greater concentration in urine as compared to blood.
Only a small decrease in
