Thursday, October 20, 2011

What Happens In The Dog's Body When The Kidneys Fail To Function Properly?

by Jennifer Coates, DVM

The last time I joined the discussion here on Dawg Business, I talked about (and hopefully clarified) some of the confusing terminology associated with diseases affecting the canine kidney and touched upon the basics of both acute kidney failure (or acute kidney injury, as I recently saw it called) and chronic kidney failure.

Today, I’d like to go over what all this means for the dogs in our lives.

In other words, what happens to the body when the kidneys fail to function properly? 

There are some significant differences between acute kidney injury and chronic kidney failure, so let’s look at the typical symptoms of each and why they develop even though there will be a lot of overlap.  I’ve highlighted the important differences for you.

Acute Kidney Injury

Dogs suffering from acute kidney injury have some combination of the following clinical signs:

All of these symptoms develop as a result of one or more of the following changes that occurs in the body of a dog suffering from acute kidney injury:

  • Metabolic waste products (e.g., BUN and creatinine) build up within the body instead of being eliminated by the kidneys. 
  • Changes in body chemistry occur.  For example, potassium and phosphorus levels rise. 
  • Because of the kidneys’ inability to conserve water, urine becomes dilute and the dog becomes dehydrated.  Typically, urine production is increased initially, but it may decline or eventually stop altogether as kidney damage worsens.  If urine production stops and fluid therapy continues, dogs may actually become overhydrated.
  • Blood pressure can become abnormally high which may lead to the retina detaching from the back of the eye and blindness.

Chronic Kidney Failure

With chronic kidney failure, dogs typically suffer from:
  • lethargy
  • depression
  • behavioral changes (they often seem dull and “out of it”)
  • loss of appetite
  • increased thirst
  • weight loss
  • muscle wasting
  • bad breath
  • vomiting (possibly containing blood)
  • diarrhea (possibly dark and tarry, indicating the presence of digested blood)
  • ulcers may develop in the mouth or elsewhere in the gastrointestinal tract
  • respiratory difficulties
  • increased urine production
  • blindness
  • seizures
  • abnormal bruising

When a dog suffers from chronic kidney failure:

  • Metabolic waste products (e.g., BUN and creatinine) build up within the body instead of being eliminated by the kidneys. 
  • Changes in body chemistry occur.  For example, phosphorus levels rise and potassium levels decline. 
  • Because of the kidneys’ inability to conserve water, urine becomes dilute and the dog becomes dehydrated.
  • Blood pressure can become abnormally high which may lead to the retina detaching from the back of the eye and blindness.
  • The kidneys stop producing adequate amounts of erythropoietin, a hormone that stimulates red blood cell production, and the dog becomes anemic.

The take home message?  Inadequate kidney function has an adverse effect on the entire body (the eye, circulatory system, brain, GI tract, etc.), which explains the myriad of clinical signs associated with kidney disease and why treating it can be such a juggling act.

***

Jennifer Coates, DVM graduated with honors from the Virginia-Maryland Regional College of Veterinary Medicine in 1999.  In the years since, she has practiced veterinary medicine in Virginia, Wyoming, and Colorado.  She is the author of several books about veterinary medicine and animal care, including the Dictionary of Veterinary Terms: Vet-speak Deciphered for the Non-veterinarian

Dr. Coates has recently joined the PetMD team and she is now writing for the Fully Vetted column; great blog, do check it out.

Jennifer also writes short stories that focus on the strength and importance of the human-animal bond and freelance articles relating to a variety of animal care and veterinary topics.  Dr. Coates lives in Fort Collins, Colorado with her husband, daughter, and pets.

Related Articles
Kidney Disease – Say What? 
Further Reading:
Recognizing the Signs of Kidney Failure in Dogs
Early Diagnosis of Kidney Disease in Dogs
Acute Kidney Failure in Dogs
Diagnosing Chronic Renal Disease and Kidney Failure in Dogs
Kidney and Urinary Disease in Dogs
Kidney Failure in Dogs

Articles by Dr. Coates:
Kidney Disease – Say What? 
The Perplexities of Pancreatitis
The Other Side Of The Coin: The Cost Of Defensive Medicine
To Neuter Or Not To Neuter… That Is The Question
Don’t Forget the Physical Therapy
Common Misdiagnoses (Part 1)
Common Misdiagnoses (Part 2)
Picking the Right Dog to Breed
When Is It An Emergency?
Dog Allergies: Common, Commonly Misdiagnosed, or Both?

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