Kidney disease is an ailment that negatively affects the quality of pets and their owners alike.
As the kidneys are one of the vital organs that are crucial for detoxification, when they improperly function, whole body health is negatively affected.
What is Canine & Feline Kidney Disease?
Kidney disease occurs when there is some degree of failure in the normal functioning of the kidneys.
The functional unit of the kidney is called a nephron and there are millions of them inside each kidney which maintain a complicated and invisible process crucial to day-to-day bodily processes.
The kidneys work like filters to remove toxins from the blood. Common toxins the kidneys clear include nitrogenous waste that enters the blood from digestion of dietary protein or breakdown of muscle and other body tissues, man-made or environmental toxins, drugs used for medicinal purposes, and more.
Regulation of water and other substances essential to health are other functions of the kidneys. Maintaining an appropriate hydration level is the goal, so the kidneys excrete excess water and conserve moisture when hydration intake is insufficient. Maintenance of glucose, protein, and electrolyte levels are also governed by the kidneys. Generally, the kidneys strive to keep glucose and protein in the blood and sustain a balance of sodium, chloride, and potassium between the blood and the urine.
The kidneys also manufacture a hormone called erythropoietin (EPO) that stimulates the bone marrow to manufacture more red blood cells. All bodily function depends on transportation of oxygen by red blood cells, so the kidneys play a key part in the process.
Improperly performing kidneys lead to increasing levels of waste products in the blood and cause an animal to feel sick. Ultimately, the clinical signs owners see prompt an appointment with a veterinarian so a pet can undergo examination and diagnostic testing so that appropriate treatments can be prescribed.
The term renal disease can be used synonymously with kidney disease, as the kidneys are part of the renal system. Reno-/rena—and nephro-/nephri—are prefixes used to relate to kidneys, such as renomegaly (enlarged kidneys) and nephritis (kidney inflammation).
What are the Causes of Kidney Disease in Dogs & Cats?
causes of kidney failure, including:
Age-related changes—As the body ages the kidneys reduce in their ability to filter toxins. Unfortunately, this is an inevitable process affecting all pets.
Congenital and developmental predisposition—Some pure breed dogs and cats are prone to kidney disease as a result of their genetics. Kidney abnormalities can be inherited from one or both parents and present at birth (congenital) or they can develop early in life (developmental). Dog breeds like the Alaskan Malamute, Cocker Spaniel, Doberman Pinscher, Lhasa Apso, Norwegian Elkhounds, Samoyed, Shih-tzu, Standard Poodles, Wheaten Terrier, and others are prone to renal dysplasia, a condition where the kidneys don’t develop properly before a puppy is born. Himalayan and Persian cats are prone to polycystic kidney disease, an inherited abnormality where fluid filled sacs develop inside the kidneys.
Food-based toxins—The foods and treats our pets consume can contain mold-produced mycotoxins, plastics (melamine, etc.), heavy metals, fecal bacteria (generally from rodents), and more, all of which can cause varying degrees of kidney damage.
Environmental toxins—Nature’s creations many not always be heathy for pets, including natural toxins like mycotoxins or man-made chemicals like Ethylene Glycol (antifreeze), fertilizers, pesticides, and others.
Medications—The medications we veterinarians prescribe to treat diseases in our patients or those prescribed by human doctors to treat people, including non-steroidal anti-inflammatory drugs (NSAIDs), chemotherapeutics, antibiotics, and more can cause kidney damage when given at appropriate or excessive doses or when accidentally ingested.
Infections—Infections with bacteria, fungi, parasites, and viruses can have a toxic effect on kidneys. Such organisms may start within the body or invade from the outside, as commonly occurs with bacterial urinary tract infection having origins on the skin surface or in feces.
What Are the Clinical Signs of Kidney Disease in Dogs & Cats?
There are many clinical signs of kidney disease that also happen to correlate with the signs of other ailments. Such is why it’s crucial that owners are fully aware of their pets’ day-to-day energetic state and habits of eating, drinking, eliminating waste, etc.
Lethargy—Elevated levels of toxins in the blood cause pets to have less energy for activity. Exercise, play, or even standing or walking can be negatively impacted.
Appetite changes—Anorexia (no appetite) or hyporexia (decreased appetite) are common in pets suffering from kidney disease.
Vomit—Since the vomiting center in the brain tract can be adversely affected by toxin accumulation associated with kidney disease pets can exhibit vomiting to expel stomach contents from the stomach, up the esophagus, and out the mouth. Food, water, stomach acid, and bile (from the gall bladder), and other liquid or material substances may be seen during vomiting episodes.
Ptyalism (drooling)—Often related to the sensation of nausea, ptyalism can be seen as thin to thick, colorless to light-colored liquid dripping from a pet’s mouth.
Strong oral malodor—When kidney toxins build up in the blood they tend to escape the body through the respiratory tract (lungs). Additionally, ulcers can form in the digestive tract or mouth in which tissues lose their blood supply and become necrotic. As a result, your pet’s breath may smell very strong or acidic.
Increase water consumption (polydipsia)—When kidney toxins aren’t properly flushed from the body the brain is promoted to drink more water in attempt to expel them.
Increased urine production (polyuria)—Polydipsia leads to larger quantities of liquid that must be cleared by the body through the urinary tract, so pets tend to urinate larger volumes. Urinary patterns can also be altered, so you may find urine in unusual locations around the house or see your pet posture to urinate more frequently or for a longer time, or exhibit other urinary tract signs.
Stool Abnormalities—When the appetite is negatively affected by kidney disease and foods that are less-familiar are used to stimulate a pet’s interest in eating owners may see associated changes in bowel movement appearance, frequency, and location.
Collapse and seizure—As kidney disease progresses to more advanced stages, your pet could collapse and have difficulty rising. When toxins in the blood build to extremely high levels, electrolyte, glucose, and other abnormalities happen and seizure activity can occur.
How is Canine & Feline Kidney Disease Diagnosed?
Kidney disease is diagnosed in several ways. Generally, an owner takes a pet to the veterinarian for a routine wellness examination or some form of illness occurs causing clinical signs of concern.
Blood and urine testing—Blood and urine tests are crucial in diagnosing kidney disease.
Elevations in blood values like blood urea nitrogen (BUN), creatinine (CREA), phosphorous (PHOS), and symmetric dimethylarginine (SDMA) can indicate kidney disease as can decreases in proteins like albumin (ALB), total protein (TP), and electrolytes like potassium (K). BUN, CREA, ALB, and TP can also increase when a pet is dehydrated, so blood results must be taking into consideration along with hydration status. Unfortunately, when BUN and CREA are both elevated in a normally-hydrated pet approximately 66% of normal kidney function is gone (i.e. the pet only has 33% of normal kidney function remaining).
Anemia (low red blood cell count) can also occur as kidney disease progresses due to reduced EPO production.
Urinalysis also yields crucial information about kidney function. Urine specific gravity (USG), color, clarity, pH, and the presence of lack of protein, glucose, blood, bilirubin, red and white blood and epithelial cells, bacteria, crystals, cats, and mucus can inform the overseeing veterinarian about the presence or absence of kidney disease.
Urine culture and MIC susceptibility are also frequently used to determine if bacterial urinary tract infection (UTI) is present and the antibiotics to which a cultured bacteria is susceptible.
Diagnostic imaging—Radiographs (x-rays) are commonly used to establish kidney size and shape or the presence of calculi (stones) or other types of mineralization. Ultrasound imaging provides greater information than radiographs, as the inner aspects of the kidney, ureters (tubes connecting the kidneys to the bladder), and bladder can be assessed.
Blood pressure evaluation—Kidney disease can cause elevated blood pressure (hypertension). Conversely, hypertension can contribute to kidney disease. Hypertension is bad for all organ systems and can lead to retinal detachment, stroke, heart attack, and other life-threatening abnormalities.
There are multiple classifications of kidney disease, including acute, chronic, and acute on chronic.
Acute kidney disease (AKD) occurs when there is a sudden injury to the kidneys that causes them to malfunction.
Chronic kidney disease (CKD) occurs over time as a result of low-grade injury or gradual decrease in normal function.
Acute on chronic occurs when a patient already had chronic kidney disease and an insult occurs that worsens the existing condition. Bacterial UTI is a common reason pets will have acute on chronic episodes.
The condition that affects most pets is CKD. The International Renal Interest Society (IRIS) has created a scoring system for CKD based on blood CREA concentration. CREA is a product of muscle breakdown, which can occur through normal day-to-day functions, exercise, starvation, and as a sequelae of disease. Iris Staging of CKD include Stages 1 through 4, which worsen with increasing number. The Stage classification depends on the presence of clinical signs and blood levels of CREA.
Besides IRIS staging, sub-staging of CKD occurs by determining urine protein levels and blood pressure.
How is Canine & Feline Kidney Disease Treated?
Fortunately, there are many options for treatment when it comes to improving the kidney function of our canine and feline companions.
Cats generally have a better prognosis for long term normal quality of life despite having kidney disease as compared to dogs. With appropriate statement, cats can live for months to years. Dogs generally only survive for weeks to months post-diagnosis, especially considering many dogs aren’t diagnosed until their disease has progressed to IRIS Stage 4.
Fluid therapy—Fluid therapy (diuresis) is crucial in treating kidney disease, as toxins building up in the blood can be flushed out when larger volumes of liquid than the pet is currently consuming are administered. Fluids like Lactated Ringer Solution (LRS), Sodium Chloride (NaCl), or others can be given intravenously (IV) or subcutaneously (SC or SQ).
IV fluid administration is more-ideal than SC, as fluids going directly into the vein are better utilized than those being given under and needing to be absorbed from the fat space under the skin. IV fluid administration requires the placement of an IV catheter and is most-safely performed when fluid volume and frequency (number of milliliters per minute) can be regulated with a pump. If fluids are administered too quickly or in excessively large volumes or if the patient has underlying cardiovascular (heart and blood vessel) disease then fluid retention (edema) can occur and additional health problems like pulmonary edema (fluid in the lungs) can arise. IV fluids generally require hospitalization, but pets can receive such treatments at home with a team of overseeing veterinarians and technicians.
SC fluids are a common treatment that owners can be trained to give at home. The set up for SC fluids is nearly identical to IV, but SC fluids don’t require an IV catheter or fluid pump. As a result, SC fluids have the benefit of being cheaper than IV fluids and giving owners a sense of satisfaction in helping their pet.
Antacid and anti-nausea medication—When toxins build up in the blood as a result of kidney failure there’s increased potential for nausea, vomiting, and ulcer formation in the stomach, intestines, and mouth. Antacid medication (Famotidine, Omeprazole, etc.) reduces production of gastric (stomach) acid and can help with ulcers. Anti-nausea medication (Ondansetron, Maropitant, etc.) works directly on the vomiting center in the brain to reduce nausea and improve appetite. Appetite stimulants (Mirtazapine, cannabidiol [CBD], etc.) promote a pet’s desire to eat.
Antioxidants—Oxidation is the process where body tissues are damaged by free radicals produced by normal cellular function, ingestion of toxins and medications, exposure environmental stressors (ultraviolet radiation, etc.), and other contributors. Antioxidants help to mitigate some of the tissue damage caused by free radicals. Vitamins B, C, D, E, and others can have an antioxidant effect. Pets can ingest antioxidants as they appear naturally in foods or supplements added to their meals or via IV or SC injection. Vitamin B12 can be helpful to promote appetite, digestive tract function, immune health, and a better energetic state.
Natural anti-inflammatory substances—Like tissue oxidation, inflammation is an enemy of the body in many aspects. Inflammation can directly affect the kidneys (as occurs with bacterial infection) or negative effects can occur when the intestines, joints, muscles, and other body systems are inflamed. Fish oil-based omega-3 fatty acids, herbs (ginger, turmeric, etc.), joint support products (glucosamine, chondroitin, etc.), and others can benefit kidney failure patients.
Prebiotics and Probiotics—The digestive tract is the foundation of pets’ immune system health, so it’s crucial that the stomach and small intestines be kept functioning normally. Bacteria generally don’t thrive in the canine and feline stomach due to the presence of strong gastric acid, but the small and large intestines are full of bacteria serving a role in digestion and waste elimination.
Prebiotics like inulin, fructooligosaccharides (FOS), and others are the substances on which bacteria (both good and bad) grow and can be found in foods (plant-based fiber, etc.) or added to meals as a supplement. Probiotics are bacteria that benefit digestive tract health. In the small intestines bacteria like Lactobacillus are most plentiful to aid in digestion. As the large intestine (colon) is responsible for formation and storage of feces, water absorption, and toxin elimination, bacteria like Bifidobacteria and Enterococcus thrive there.
Prebiotic and probiotic supplements should be selected with the emphasis in supporting both the small and large intestine. Prebiotics and probiotics can help kidney failure patients by promoting intestinal health so bacteria-produced nitrogenous wastes are more likely to be eliminated instead of being absorbed.
Moist, human-grade, whole-food diets—When a pet is having kidney failure, it’s vital that the food consumed is moist to provide much needed hydration to facilitate toxin removal. My primary recommendation is for pets to eat a moist diet regardless of their health status. Human-grade, whole-food diets are generally less-likely to contain mycotoxins as compared to feed-grade diets like kibble and some canned foods. Such is why I’m such an advocate of pets eating diets like those from The Honest Kitchen.
Erythropoietin (EPO)—Kidney disease causes anemia of chronic disease which manifests as patients feeling more lethargic, having pale gums, breathing deeper and quicker, and other clinical signs. Since EPO is insufficiently produced by damaged kidneys, pets suffering from renal disease can benefit from EPO injections.
Dialysis—Just like people, pets are now able to undergo advanced treatments to detoxify the blood like dialysis. Whereas diuresis involves fluid administration to flush out toxins, dialysis involves extraction of blood from the body, processing the blood to remove toxins, then reintroduction of toxin-free blood via intravenous infusion. Dialysis does a more-thorough job in detoxifying the blood than dieresis and is offered at some veterinary specialty and teaching hospitals, like ACCESS in Los Angeles, where my go-to internal medicine specialist, Dr. Adam Eatroff, performs this life-saving procedure.
Kidney Transplants—Veteirnary medicine has advanced in some capacities to parallel human medicine (like with dialysis), and now some pets are even undergoing transplants to replace failing organ systems. Kidney transplants are performed by some veterinary specialty and teaching hospitals and involve the removal of a diseased kidney and the replacement with a donor kidney. The recipient patient must then take immunosuppressive drugs on a life-long basis to ensure the donated kidney isn’t rejected by the body.
Can Kidney Disease in Dogs & Cat Be Prevented?
Yes, kidney disease can be prevented and prevention is the best treatment.
Toxin avoidance—Avoidance of household and environmental toxins is a key component of having healthy kidneys on a lifelong basis, which is why I don’t recommend pets go outside on an unobserved basis and pet-safe antifreeze containing propylene glycol instead of kidney-toxic ethylene glycol is used in cars driven by pet-owning households. Human and veterinary drugs having potential to cause kidney damage should be minimized and owners should have an open conversation with their veterinarian about safety concerns related to prescribed treatments.
Hydration—Maintaining an optimal level of hydration is also crucial to promote toxin removal through both the kidneys and liver. Water constitutes nearly 70-80% of a pet’s body mass, so it’s an essential nutrient for a normally functioning body. Loss of only 10% of bodily fluids can lead to serious illness as reduced liquid volume in the blood and lymphatic system reduces tissue oxygenation, nutrient delivery, immune system function, and toxin removal.
Diet—Like in the treatment of kidney disease, pets benefit from eating moist, freshly-prepared foods made with human-grade ingredients instead of kibble or any diet made with feed-grade ingredients, which have higher allowable levels toxins. Highly-bioavailable protein sources, like whole-food meat appearing like they do in nature, are more efficiently used by the body than high-heat cooked, rendered proteins (meat “meals, by-products, and by-product meals”) and grain-based protein sources (corn/wheat/other gluten and their “meals”).
Routine blood and urine testing—Being aware of your pet’s kidney function is key in taking appropriate steps to prevent disease or readily catch it before clinical signs of illness are seen. I recommend annual blood and urine testing for all pets regardless of age or more-frequent diagnostics for sick and senior patients (those seven years of age or older) or pets taking medications potentially having a kidney-damaging effect.
Hopefully, with toxin prevention and early treatment your pet’s kidneys will stay highly -functioning for many years to come and a great quality of life can be maintained.
If your pet has endured kidney disease feel free to share your perspective in the comments section.
Interested in seeing the impact of diet on pets with kidney disease? Read through our True Stories here.