Introduction
Chronic renal failure (CRF) can be present without obvious symptoms for a very long time. When kidney disease is asymptomatic, it usually is called renal “insufficiency,” rather than renal “failure”. Unfortunately, once overt signs appear, the kidneys probably have lost over 75% of their ability to perform their normal functions of filtering toxins from the blood, excreting the end-products of metabolism in the urine and regulating the concentrations of hydrogen, sodium, potassium, phosphate and other essential electrolytes in bodily fluids.
Symptoms of Chronic Renal Failure
The symptoms of chronic renal failure are largely a result of the body’s attempt to compensate for the kidneys’ inability to flush toxins and other waste products out of the body. Among the first changes noticed by owners of dogs with CRF are excessive thirst marked by increased water intake and excretion of an unusually large volume of urine.
Symptoms of chronic renal failure can include one or more of the following:
- Increased water intake (polydipsia)
- Increased urine output (polyuria)
- Loss of appetite (anorexia; inappetence)
- Weight loss
- Weakness
- Lethargy; apathy
- Depression
- Vomiting
- Constipation
- Diarrhea
- Bloody stool
- Inappropriate urination (especially at night; nocturia)
- Bad breath (halitosis; ammonia-like odor)
- Discolored, brownish tongue surface
- Bleeding problems (abnormal blood clotting; prolonged clotting times)
- Changes in cognition or mental state
- Dehydration
- Oral ulceration (sores in the mouth and on the gums)
- Loose teeth (“rubber jaw”)
- Poor haircoat (dry, disheveled, unkempt)
- Poor body condition (loss of muscle tone, underweight)
- Pale gums and other mucous membranes (pallor)
- Acute onset blindness (from hypertension)
- Seizures, tremors, shivering, shaking (late in disease)
- Coma (end-stage disease)
Polyuria and polydipsia (also called “PU/PD”) are very commonly associated with a number of disorders and, without more, are not diagnostic of CRF. However, excess water intake and urine output almost always accompany chronic renal failure when it is present. The bad breath and oral ulceration are caused by the build-up of toxic waste products in the blood. In severe cases, dogs with CRF may develop high blood pressure (hypertension), with the adverse effects associated with that condition.
Dogs At Increased Risk
Chronic renal failure is more common in older dogs, because it is normal for kidney function to worsen with age. However, dogs of any age can be affected. Certain breeds seem to have a familial hereditary predisposition to developing early-onset CRF, including the Basenji, Beagle, Bedlington Terrier, Bernese Mountain Dog, Bull Terrier, Cairn Terrier, Chow Chow, Cocker Spaniel, Doberman Pinscher, German Shepherd, Golden Retriever, Keeshond, Lhasa Apso, Miniature Schnauzer, Newfoundland, Norwegian Elkhound, Pembroke Welsh Corgi, Rottweiler, Samoyed, Shar-Pei, Shih Tzu, Soft-Coated Wheaten Terrier and Standard Poodle. Dogs with a history of acute renal failure episodes are more likely to develop chronic renal failure, as are dogs that have had kidney stones (nephroliths; uroliths) or other types of kidney disease.