What is kidney disease in dogs and cats?
One of the most common ailments in dogs and cats is kidney (renal) disease, a broad term that applies to any disease process that leaves the kidneys unable to effectively filter toxins out of the blood and maintain water balance in the body. Kidney (renal) disease is also called kidney (or renal) failure and renal insufficiency. All bodily systems are affected when the kidneys aren’t working well. Diagnosis and treatment of kidney disease should include monitoring of other organs such as the heart, liver, and pancreas.
The function of the kidneys is to filter the blood, conserve water and electrolytes in the body, keep the pH balanced and send waste products out through the urine. Kidney function should be checked during your regular visits to the veterinarian. Your veterinarian should palpate your pets’ kidneys during their physical examination. Palpation is an examination of the shape, contour, and size of the kidneys. Lab tests, such as urinalysis, complete blood count (CBC), and chemistry screens are critically important in catching kidney disease in its early stages.
Once damaged, kidney tissue (nephrons) will not regenerate. There is no cure for kidney disease. However, the kidneys have a great deal of reserve capacity to function, even when disease has damaged them to some degree. At least 2/3 of the kidney must be dysfunctional before any clinical signs appear. Animals can survive with only one kidney. The goal with treating kidney disease is to optimize and support the kidney function still present. Kidney disease is common in older dogs and cats and is considered the “wearing out” of kidney tissue. For smaller dogs and cats, kidney disease occurs on average between 12-14 years of age. For larger dogs, kidney disease can be diagnosed as early as 7 years of age.
Kidney disease can occur over weeks, months, and years (called chronic kidney disease or CKD) or suddenly within days (acute kidney injury or AKD). For AKD, treatment as soon as possible is crucial. CKD is the result of degenerative changes in the kidney and can be subtle to diagnose in its early stages.
What are the common causes of kidney disease?
- Toxins can damage your pet’s kidneys. The primary toxic culprits are antifreeze, rat poison containing cholecalciferol, foods such as grapes, raisins and certain commercial jerky treats, excess vitamin D, common over-the-counter medications (OTCs) such as aspirin and other nonsteroidals (NSAIDS such as ibuprofen and naproxen), prescribed medications, pesticides, heavy metals, and venoms.
- Diuretics such as furosemide are generally considered a safe medication when given as directed; however, overdoses that remain untreated can lead to dehydration, electrolyte imbalances, and kidney malfunctions. Stronger medications, such as torsemide, can result is diuretic toxicity and need to be monitored carefully by your veterinarian.
- Trauma: A kidney contusion, often called a kidney bruise, occurs following blunt trauma or direct impact to the lower back. This trauma leads to bleeding inside of the kidney. Acute kidney injury (AKI) is a sudden episode of kidney failure or kidney damage that happens within a few hours or a few days. AKI causes a build-up of waste products in the blood and makes it hard for the kidneys to keep the right balance of fluid in the body.
- Infections of the kidney tissues can occur in dogs and cats. Severe urinary tract infections can move from the bladder up to the kidneys. When a severe urinary tract infection is diagnosed, an ultrasound of the kidneys and bladder can be performed to determine the status of the kidneys. The goal is to kill the bacteria that can cause damaging inflammation. A urinalysis and culture and sensitivity test will verify the presence and type of bacteria so that proper treatment can be prescribed. In cats, diseases such as feline infectious peritonitis (FIP), feline immunodeficiency virus (FIV), and feline leukemia can result in kidney failure to varying degrees. Glomerular disease is a condition affecting the kidney filtration mechanism in both dogs and cats and can be caused by infections (i.e. Lyme disease, Leptospirosis, e-coli), cancer, and high blood pressure
- Urinary Tract Obstruction: Kidney stones can be caused by a chronic bacterial infection, genetics, and other diseases that alter blood and urine. Most stones in the kidney are oxalate stones and are usually not removed if small. The stones don’t often seem to cause a dog or cat pain, unless they cause a blockage within the kidney or kidney ducts. When a blockage occurs, urine cannot exit the kidneys easily, and as the urine backs up, the kidneys will swell and can become damaged.
- The genetics of certain dog and cat breeds can play a role in kidney disease. Polycystic kidney disease is a genetic marker for several purebred dog and cat breeds.
What are the symptoms and treatment of kidney disease?
Chronic kidney failure progression is like a series of dominoes each falling one after the other. When the kidney’s filtration process becomes inefficient, less toxins are eliminated in the urine. This inefficiency increases blood flow to the kidneys to remove the toxins, resulting in increased urine production. The increased urine production results in fluid loss (and possible dehydration); thirst and water consumption increases. This process creates the earliest clinical signs of kidney disease known as compensated renal failure. This process can play out over months and years.
Symptoms of AKD and CKD are similar; the difference is how quickly the symptoms appear. Early indicators of kidney disease include increased thirst and urination, lethargy, decreased or loss of appetite, nausea, vomiting, diarrhea, and weight loss (especially in CKD and in cats). As the disease progress, toxins built up in the body will increase and the symptoms will worsen. Signs of advancing kidney disease include:
- Dehydration – severe dehydration can be painful cause a “grimace” in cats. Signs of pain include “squinty” eyes, wrinkled forehead, flattened ears, and drooping whiskers.
- Increased water consumption and urination
- Lethargy
- High blood pressure
- Ulceration of the mouth or the digestive tract – these conditions can cause bad breath and dark, tarry stools
- Increased loss of appetite and/or anorexia/weight loss
- Diarrhea
- Blood in the urine
- Inability to regulate body temperature resulting in the animal becoming cold
- Failure to groom (in cats)
- Pale gums due to secondary anemia
- Seizures due to high ammonia levels in the blood
How is kidney disease diagnosed?
Several tests are recommended to accurately diagnose kidney disease and it’s associated stage.
- A urinalysis assesses whether the kidneys are producing concentrated or diluted urine. Good kidney function will result in good urine concentration. A urinalysis will also indicate the level of protein in the urine. Some conditions can produce falsely elevated levels of protein in the urine; secondary tests called microalbumin and urine protein creatinine ratio (UPC) can be performed to confirm the presence of protein in the urine.
- A urine culture involves growing bacteria from a urine sample in a lab to diagnose urinary tract infections and other infections.
- A complete blood count (CBC) will indicate red cell count decreases in chronic or late-stage kidney disease.
- A full blood chemistry panel assesses the function of various internal organs, and it is important to look at several values when diagnosing kidney disease. These include:
- Blood urea nitrogen (BUN) and blood creatinine (CREA) testing measures the level of these two waste products in the blood.
- Electrolytes (sodium, chloride, and potassium) levels can drastically increase or decrease. Levels can drop when an animal is drinking and urinating to the point of diluting the electrolytes out of the blood stream. Severe kidney disease can also elevate potassium levels and affect heart function.
- Amylase is an enzyme produced by the pancreas and is filtered by the kidneys. Sometimes kidney disease can be mistaken for pancreatitis if amylase levels are increasing. Diagnosis for both kidney disease and pancreatitis should include an assessment of more than just amylase levels.
- SDMA is a blood test that is used to determine the stage of kidney disease. SDMA is a naturally occurring biological indicator for kidney function. SDMA concentrations above the normal range can diagnose kidney disease at an earlier stage (25% loss of function). SDMA can be falsely elevated in your pet is dehydrated or suffering from another illness.
- Thyroid levels, particularly in cats, should also be assessed. Hyperthyroidism is cats can result in high blood pressure which in turn produces kidney disease.
- Elevated blood phosphorus is a problem for animals with kidney disease; maintaining normal levels is essential in managing kidney disease.
- A diagnostic ultrasound can provide further clues to problems by examining an image of the kidneys.
- Blood pressure should be checked, as high levels can indicate kidney disease.
What are the stages of kidney disease?
A diagnosis of kidney disease is based on an evaluation on all available clinical and diagnostic information in a stable patient. The staging of kidney disease is based on the IRIS (International Renal Interest Society) parameters. In addition to the parameters, IRIS also recommends treatment protocols for each disease stage. However, the parameters and protocols should be treated as guidelines, since no one dog or cat is the same. Holistic veterinarians will often recommend treatment protocols not listed in the IRIS guidelines.
There are four stages of chronic kidney disease in dogs and cats. Each stage in the IRIS guidelines is based on SDMA and creatinine results. Again, ALL available clinical and diagnostic information should be used in evaluating the patient. For example, one high SDMA test result may not indicate kidney failure. The SDMA test should be rerun when the animal is well-hydrated.
How is kidney disease treated?
Once a treatment protocol has been started, it is important to continue to monitor treatment progress with urinalysis and blood work.
- Fluid therapy is the cornerstone of both conventional and holistic treatment. Fluid therapy replaces various electrolytes, flushes toxins from the body, and reverses dehydration. If BUN is elevated or the animal is not eating, it is recommended to start IV fluids in a hospital setting for about 2-3 days. The biggest problem with IV fluid administration is managing animals that have co-morbidities, such as heart disease. In these instances, your veterinarian may be uncomfortable treating with IV fluids. Never hesitate to ask your veterinarian about this, as you may need to seek out a specialist to administer treatment. Once the animal is stabilized, your veterinarian may recommend maintenance levels of fluids to be administered at home under the skin (subcutaneously).
- Medications: To stabilize high blood pressure, conventional treatment would include medications such as enalapril or lisinopril. Holistic treatment might include herbs and/or supplements that lower blood pressure. To help with nausea, vomiting or anorexia, conventional treatment might include medications such as cerenia or ondansetron. Herbal supplements, ginger tea, or a ginger cookie would also help to settle the stomach. For stomach ulcerations, medication to reduce acid (such as omeprazole) might be prescribed. Magic Mouth Wash can be used to reduce pain from ulcerations in the mouth. Ace inhibitors can help with protein loss.
- Avoid nephro-toxic medications: When a medication is prescribed for any reason, always check the side effects of the drug. All medications have side effects. This is particularly important if your pet has co-morbidities.
- Phosphorus binders are used when the phosphorus levels in the blood are elevated. The body will automatically try to keep phosphorus and calcium in balance. If an animal has low calcium levels, the body will take it from the bones and teeth resulting in osteoporosis, brittle bones and tooth and jawbone loss.
- A hormone produced by the kidneys called erythropoietin stimulates the bone marrow to make red blood cells. With advanced kidney disease, the hormone is no longer produced. Darbopoietin is a human medication that can be given by injection to stimulate the bone marrow to produce red blood cells. Unfortunately, the drug may not be used long term because the immune system recognizes the drug as “foreign” and may make antibodies against it.
- Acupuncture can be very beneficial to improve appetite, decrease nausea, and slow the progression of disease.
What are the best supplements to support kidney disease?
For any stage of kidney disease herbal support will help with fluid (urine and blood) flow. Antioxidants (such as CoQ10) and anti-inflammatory (PEA) supplementation is also recommended. Omega-3 fatty acids (i.e. fish oils, phytoplankton) have both antioxidant and anti-inflammatory properties. Other supplements can be used to decrease the risk of infection, reduce incontinence, and bind nitrogen waste products.
For more information on supplementation, check out this video.
What is the best diet to support my pet with kidney disease?
Many veterinarians will immediately recommend a protein-restricted diet in pets with any stage of kidney disease. Protein should not be restricted in early stages of kidney disease, as this will result in muscle wasting and weakness. It is important to be somewhat restrictive with phosphorous levels in the diet. Sodium restriction is not a huge concern in pets, as most pet foods do not contain high levels of salt (be careful with processed treats, however). The ideal diet for pets with kidney disease should contain abundant moisture (no dry kibble, even if it is prescription diet).
Recipes for home-prepared kidney diets can be found here.
