Kidney Disease in Pets
The kidneys play a vital role in your pet’s health, including removing waste from the blood, regulating electrolytes and blood pressure, and making hormones essential to calcium metabolism and red blood cell production. When the kidneys become damaged, whether through an infection, poisoning, or some other event, a pet can experience vomiting, appetite loss, frequent urination, back or abdominal pain, and other symptoms. Without treatment, kidney disease leads to kidney failure — and death. Treatments range from special diets to antibiotics to surgery, depending on the cause of the kidney disease.
When most pet owners think of kidney (renal) disease they tend to think of chronic renal failure, the common degenerative process of older pets (cats, mostly) in which the kidneys gradually lose function over time. Yet kidney disease is a much more general term used to describe any one of many conditions that can affect the kidneys or damage kidney cells.
Here are just a few medical conditions that can be associated with kidney disease:
- Nephritis: infection of the kidneys
- Nephrotoxicosis: (kidney toxicosis) damage to kidney cells associated with a drug or poison (such as antifreeze)
- Polycystic kidney disease: a genetic condition in which functioning kidney cells undergo degeneration to become cysts and lose their ability to function properly
- Kidney stones
- Heart failure: decreased blood supply to the kidneys (secondary to heart disease) can cause kidney cell damage, leading to kidney disease
- Chronic kidney failure: (described above, also called chronic kidney disease)
If kidney disease progresses it can eventually lead to kidney failure and death. Kidney failure describes a condition in which kidney function decreases to such an extent that the kidneys are no longer able to effectively eliminate waste products, maintain hydration, and help regulate the balance of electrolytes in the blood.
Despite how the term may sound, kidney failure doesn’t always mean that the kidneys stop producing urine altogether. In fact, because the kidneys can no longer concentrate urine, increased urine production (not decreased) is often one of the key clinical signs associated with kidney failure. Urine production doesn’t stop completely until kidney failure has progressed to the very last stages.
Kidney failure can occur acutely (over a period of hours or days) or chronically (usually over a period of weeks to months or longer). Antifreeze toxicosis is an example of a condition that can cause sudden onset (acute) kidney failure. If diagnosed quickly and treated aggressively, acute kidney failure can be reversed in some cases. By contrast, chronic kidney failure is not reversible.
Symptoms and Identification
The kidneys are responsible for several important functions in the body, including:
- Eliminating waste products through the urine
- Producing a hormone involved in the production of red blood cells
- Helping maintain the body’s fluid balance/hydration
- Participating in the metabolism and elimination of many types of drugs
- Helping regulate levels of important electrolytes such as potassium and sodium
When kidney disease develops, these functions don’t occur properly, resulting in illness and (frequently) further progression of disease. Common signs include:
- Appetite loss
- Increased drinking and urination
- Lethargy (tiredness)
- Weight loss
- Unkempt coat (due to decreased grooming)
- Back pain or abdominal pain (may be associated with acute kidney failure)
- Pale gums
The severity of clinical signs associated with kidney disease can vary depending on the presentation (acute or chronic), the extent to which the loss of kidney function has progressed, and the underlying cause.
As with many other medical conditions, diagnosis of kidney disease frequently begins with a medical history. To help a veterinarian determine if your pet may be dealing with a kidney problem tell him or her about any medications or supplements a pet has received; anything unusual that a pet may have eaten, drunk, or chewed; previous illnesses; or any current signs of illness.
Diagnosis of kidney disease may require a combination of several tests. Veterinarians may not recommend all these tests, but the following are frequently performed:
CBC and chemistry profile: These tests are commonly performed together as part of a wellness screen or initial blood testing when a pet is ill. These tests provide an overview of many of your pet’s organ systems, including the kidneys. The CBC (complete blood cell count) shows the number of red blood cells (needed to carry oxygen to all the body’s tissues), white blood cells (needed to help fight off infection), and platelets. Because the kidneys are involved in the production of red blood cells, the numbers of these cells may be reduced if a pet has kidney disease (particularly chronic kidney failure). The white blood cell count may also be abnormal if infection is present. The chemistry profile includes several kidney values that can change if there is a problem with the kidneys, such as kidney disease or kidney failure.
Radiography (X-rays): X-rays of your pet’s abdomen may show abnormally shaped kidneys, kidney stones, or kidneys that are enlarged or shrunken.
Sonographic evaluation of the abdomen (ultrasound): Ultrasound is very useful for examining the kidneys. An ultrasound machine is connected to a small handheld probe that is held against your pet’s abdomen. The probe sends out painless sound waves that bounce off structures in the abdomen (such as the kidneys) and return to a sensor inside the ultrasound machine. This creates an image on a screen that shows your veterinarian the structure of your pet’s internal organs. The ultrasound can also “look inside” organs (like the kidneys) to detect masses, stones, cysts, or other problems.
Urinalysis: Evaluation of a urine sample from your pet can provide critical information about kidney functioning. Urine that is too diluted, contains abnormal cellular debris, or contains protein and other material that should not be present can indicate that a pet may have kidney disease.
Kidney biopsy: A pathologist may need to evaluate a sample of kidney tissue. A sample may be retrieved either via ultrasound-guided method or surgical intervention.
Breed predisposition to renal disease depends on the distinct disease entity affecting the pet. For chronic renal failure in both dogs and cats, for example, there appears to be no breed predisposition.
The Basenji is particularly affected by Fanconi syndrome, a disease in which the kidney’s ability to reabsorb water and other molecules is impaired. It’s also been described in the Norwegian Elkhound, Shetland Sheepdog, and Schnauzer, though its incidence is far lower for those breeds.
A familial type of kidney infection called glomerulonephritis has been reported in some breeds such as Bernese Mountain Dogs and Soft Coated Wheaton Terriers.
Among Shar-Pei dogs, familial renal amyloidosis (deposition of amyloid protein into the kidneys) is a major concern.
In cats, polycystic kidney disease is more prevalent among Persians and members of the exotic shorthair breed.
Treatment of kidney disease can vary depending on the underlying cause and the patient’s overall condition. For example, if a pet has kidney stones, surgery may be recommended as the best treatment. Pets that are severely ill from kidney disease or kidney failure may need hospitalization and intensive care to recover. In other cases, antibiotics, fluids, and other medications given on an outpatient basis are effective. There are even special diets and dietary supplements that can help some pets with kidney disease.
Chronic kidney disease and chronic kidney failure are progressive, irreversible conditions. Treatment generally focuses on slowing the progression of disease and improving quality of life for the patient. Pets can sometimes experience a good quality of life for many years after being diagnosed with kidney disease or kidney failure.
Although most cases of kidney disease are not preventable, regular physical examinations and wellness screening tests can increase the chances of early diagnosis and treatment.