Park Hill Vet: Our Fabulous Filtering Kidneys

When Those Bean-Shaped Organs Aren’t In Tip-Top Shape

By Margot K. Vahrenwald, DVM, CVJ

Two bean-shaped organs are small powerhouses for all mammals’ bodies. The kidneys filter blood to process out protein waste products and excrete them into the urine. They balance body water and maintain proper levels of certain electrolytes, salts and acids that allow cells to function properly throughout the body.

We — meaning humans, cats and dogs — have two kidneys as a complex system that is inherently redundant as we can live healthily with 70 to 75 percent of only one being functional. Each kidney is a collection of thousands of little filters called nephrons. Simply aging can be unkind to nephrons through a variety of routes and, as they become damaged with age, some will no longer be functional while others become what we call “super nephrons” with enhanced capacity to make up for those lost nephrons.

However, over time, we see that one in 10 dogs and three in 10 cats will develop chronic kidney disease as the nephron and “super nephron” population becomes depleted.

Many things can cause enough injury to a nephron that it no longer can fulfill its work. Some of the insults over time can include:

• Glomerulonephritis (inflammation of the filtration unit itself)

• Pyelonephritis (infection in the nephrons)

• Kidney stones

• Ureteral obstruction and hydronephrosis (obstruction of the ureter from kidney to bladder and the impact of subsequent back up of urine into the kidney)

• Cancer

• Toxic insults (antifreeze, many drugs)

• Tubulointerstitial disease (changes to the tubule region of the nephron – key in filtering out or reabsorbing essential electrolytes)

• Amyloidosis (protein sheets depositing in the functional tissue of the kidneys)

• Hereditary nephropathies (genetic issues seen in particular breeds of cats and dogs)

• In cats, Feline Infectious Peritonitis can impact the kidneys

• In dogs, Leptospirosis

The loss of these nephrons is typically undetected early on because of the compensatory ability of the remaining nephrons. We, until recently, could not detect negative changes until the kidneys were functioning at 33 to 25 percent of their capacity. New diagnostic tests from our veterinary reference laboratories, such as SDMA, are helping to catch changes in kidney function up to 25 percent earlier.

What does it look like if your cat or dog is developing chronic kidney disease? The symptoms can be quiet and subtle, but can include:

• Weight loss

• Decreased energy

• Decreased appetite

• Vomiting

• Increased water consumption with increased urination

• Bad breath with a chemical odor

What can be done to identify and support changes in kidney function?

The biggest step in prevention is regular veterinary examinations, especially as your cat or dog gets older. We recommend that senior pets be seen every six months with at least annual screening blood and urine testing. Those screening diagnostics can tell us much about the impact of the changes in kidney function and to stage the degree of disease present. We can see changes such as anemia or infection in the complete blood count. Values indicative of the kidneys’ functional level can be checked in the blood chemistries and via urine.

Support will often involve changes in diet to modify the workload of the nephrons, supplements and sometimes fluid therapy. Your veterinarian will help guide you through the options for your pet based on their diagnostic results and monitoring over time.

Dr. Margot Vahrenwald is the owner of Park Hill Veterinary Medical Center at 2255 Oneida St. For more information, visit parkhillvet.com