My 10-year-old dog is drinking more water and urinating much more than he used to. What’s going on?
It could be diabetes, bladder disease, bladder or kidney stones, or an infection of the urinary system; your veterinarian can check for those and other possibilities. The more usual cause in an older dog is Chronic Kidney Disease (CKD). Signs of CKD include polydipsia (excessive drinking), polyuria (excessive urinating), and nocturnal incontinence (leaking urine when asleep). As the disease progresses, and it usually does, you can expect vomiting, diarrhea, anorexia (loss of appetite), weight loss, depression, pale gums and weakness. Poor kidney function can lead to weakened bones and spontaneous fractures, high blood pressure leading to blindness, puritis (itchy skin) bruising or gastrointestinal bleeding.
The kidneys contain thousands of functional units called nephrons. When our pets are young and healthy, not all of the nephrons are functioning all the time there are nephrons in reserve, so to speak. As your pet ages, or if the kidneys become damaged from disease or from some sort of toxicity, some nephrons no longer function. When that happens, the body recruits the reserve nephrons and everything is hunky dory. If there are no longer any “extra nephrons” available, signs of CKD manifest.
The kidneys are complex filters that remove waste products, the result of metabolism, old cells breaking down, toxins, poisons and many drugs. When the nephrons are not functioning properly, or there are not enough of them functioning, these toxic substances build up in the blood. The body tries to rid itself of these substances by increasing water intake and increasing the urine flow. So, the kidneys filter out body water with almost everything in it. Then the kidneys reabsorb a host of substances that the body requires to maintain the necessary levels of such things as water, sodium, potassium, calcium, Vitamin D, sugar, and many, many others.
To make things even more complicated, the kidneys also function as an endocrine organ producing hormones responsible for regulating blood pressure, water balance and stimulating the production of red blood cells. Because the kidneys do so many different things, signs of kidney disease can be very confusing.
To make the diagnosis and formulate a prognosis and treatment plan, your veterinarian will have to run a number of laboratory tests, on blood and urine. It may also be necessary to take X-rays, do an ultrasound exam, a kidney biopsy, cultures for bacterial infections, and tests for ability of the blood to clot normally. In most cases, the more expensive testing is not necessary.
CKD cannot be cured. Your veterinarian will prescribe diet and treatment designed to flush out toxic waste products from the animal’s body and extend his or her life as a companion.
Dr. David Gross graduated from Colorado State University’s veterinary school in 1960 and was in private practice for 10 years. He enrolled in graduate school at Ohio State University earning a M.Sc. degree in 1972 and a Ph.D. degree in 1974. He retired in 2006 as Professor and Head of Veterinary Biosciences, at the University of Illinois, Urbana-Champaign. Dr. Gross is a Fellow of the Cardiovascular Section of the American Physiological Society. During his academic career, he published over 90 papers in refereed scientific journals and over 100 abstracts in proceedings of scientific meetings.