Tuesday, February 4, 2014

Kidneys—the Unsung Heroes of Waste Disposal…

Like your neighborhood garbage handlers and the late great Rodney Dangerfield, the kidney just doesn’t get enough respect.  In fact, your kidneys are so important, that the body is equipped with two, even though you only need one healthy kidney to live!  Just what does the kidney do, anyway?
  • Regulates water balance –i.e. decreased urine when you’re dehydrated, increased when you’re drinking a lot
  • Filters small particles from the blood—some are passed in the urine (like some medications), and some are re-absorbed before they are excreted (like glucose—except in diabetics where the kidneys can’t keep up with the high blood sugar)
  • Regulates electrolyte balance
  • Excretes urea—a by-product of protein breakdown that is related to ammonia
  • Helps to regulate blood pressure
  • Works with the parathyroid gland to regulate calcium levels
  • Secretes a hormone called erythropoietin to stimulate red blood cell production
If the kidney isn’t doing its job the way it should, it’s called renal failure, but this doesn’t mean it has shut down entirely…

There are two types of renal disease/failure:      

ACUTE RENAL FAILURE (very recent onset) generally happens in younger animals, but not always.

Causes include toxins such as antifreeze (ethylene glycol), grapes/raisins, plants like Easter lilies (cats!), or even human medications.  Other causes include urinary obstruction—if the urine can’t get out, it will start to back up into the kidneys and cause pressure damage to the delicate tissues; infectious disease like leptospirosis or even infection that may spread from other parts of the body via the bloodstream.  Decreased blood flow to the kidneys (such as what happens when an animal gets too dehydrated or develops heat stroke) can also cause acute renal failure.

CHRONIC RENAL FAILURE (been going on for a while, even though it may not have been detected) generally happens in older animals, but not always. Causes include birth defects (malformed or missing kidneys), hypertension (high blood pressure), heart disease, chronic low grade inflammation/infection or even just old age—many geriatric cats will develop this.  Persian and Abysinnian cats are genetically prone to kidney disease.
How Can I Tell If My Pet Has Kidney Disease?

Often in acute renal failure, a pet that felt fine a few days ago, now feels lousy.  They may be a little dehydrated, lethargic, not wanting to eat, and they may or may not be vomiting.  They may be urinating very little, not at all or more than usual.  Animals that have gotten into antifreeze may appear “drunk” or “out-of-it”.  Fluid may accumulate in the lower part of their legs or even in their lungs. In severe situations, increasing ammonia levels can cause seizures.

In chronic renal failure, the pet may be thin, and they’re usually dehydrated and often vomiting (increased toxins in the body can cause stomach ulcers AND stimulate a part of the brain that causes vomiting).  They may have dark or tar-like stools.  They often have foul breath and ulcers on their gums (which are often pale) or the inside of their cheeks.  They’ve usually been drinking a lot and urinating a lot. Contrary to popular belief, increased urination is NOT a sign that the kidneys are functioning well!

Diagnosis is based on physical exam, and bloodwork/urinalysis.  Your vet will specifically be looking at BUN/creatinine, hematocrit, potassium, calcium and phosphorus levels as well as the specific gravity of the urine.  Additional diagnostic tests may be recommended by your veterinarian.


Dehydration makes the pet feel really sick (remember the last time you had the stomach flu?!  UGH!).  Fluids administered intravenously will also help to flush out the toxins that build up in the body.  In chronic cases, fluids may be given subcutaneously (under the skin).

A potassium level that is too high (common in animals that have a urinary obstruction) can cause life-threatening heart arrhythmias, and must be lowered with fluids and possibly medication.  Potassium that is too low (common in chronic renal failure patients) can cause weakness and must be supplemented in the fluids.  When the pet goes home, they may require oral potassium supplements.

High phosphorus levels are common as the kidney failure progresses, and it can make the pet feel terrible. High phosphorus can cause calcium levels to drop (calcium and phosphorus levels should be inversely proportionate—meaning as one rises, the other falls), which can eventually result in rubbery bones as the body robs the bones of their calcium!  There are dietary supplements that bind phosphorus in the digestive tract.

Antibiotics are necessary for bladder or kidney infections (your vet may recommend periodic urine cultures to monitor for infection).

Anemia may require treatment in the form of supplements or medications.

Vomiting may be severe enough to warrant treatment—medications may be prescribed for nausea, to decrease acid production in the stomach, to coat the stomach, and/or to move the food more efficiently through the digestive tract.

Medications may be prescribed to increase blood flow to the kidneys or to decrease blood pressure.

Prescription diets for pets with kidney disease have specially formulated protein, salt, phosphorus and potassium levels, as well as anti-oxidants that may reduce the risk of further kidney damage.

ALWAYS allow constant access to water—these animals should NEVER be allowed to dehydrate!!

While kidney transplants are available for dogs and cats, they are not performed very frequently.  There are very specific requirements that must be met; there are a limited number of referral centers in the country that offer them, and they are very expensive.

The prognosis depends on the cause and the extent of the damage to the kidneys.  If we can quickly identify and treat the cause of acute renal failure, a full recovery may be possible.  Chronic renal failure is not curable, but can be manageable—particularly for cats.

References and good sites for more information:
Written by Dr. Sunday Cozzi

Read more or contact Dr. Sunday:

Dr. Sunday Cozzi
Lap of Love Veterinary Hospice
(803) 994-9460
Central Savannah River Area

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