What is chronic kidney disease or failure? Chronic Kidney/Renal Disease Kidney disease means that something is abnormal about the structure or function of one or both kidneys. Most often, kidney disease is recognised when kidney function has deteriorated sufficiently to give clinical signs and to be detectable by blood and urine tests. The functions of the kidneys are the following: To filter and eliminate waste products from blood Maintain water and electrolyte balance (hydration) Produce a variety of hormones Control of Red Blood Cell production In the past, the term kidney (or renal) failure was used to describe advanced forms of kidney disease. Kidney disease occurs in acute or chronic forms. Acute kidney disease happens over just days and is potentially reversible. In contrast, chronic kidney disease has been present for months to years and is irreversible. Dogs and cats with chronic kidney disease cannot be cured, but their symptoms can often be managed successfully. Kidneys are composed of many small functional units called nephrons (approximately 190,000 in cats and 400,000 in dogs). Dogs, cats, and humans are normally born with such an abundance of nephrons that loss of more than two thirds of these nephrons can occur before symptoms of kidney disease become apparent. However, this surplus of nephrons can make it difficult to diagnose kidney disease before substantial damage has already occurred. As a consequence, kidney disease can be an insidious condition that remains unrecognised either until blood and urine tests are performed or the patient becomes ill. Chronic kidney disease tends to progress over time. An important goal of managing patients with chronic kidney disease is to recognise the condition while it is still mild and attempt to slow or stop the progression to a more severe disease. Because chronic kidney disease is advanced when it is diagnosed, it is often impossible to determine the original cause for the kidney damage. Although it is most commonly diagnosed in older dogs and cats, chronic kidney failure may not simply be as a result of aging. Page 1 of 5
What are the symptoms of chronic renal failure (CRF)? Dogs and cats with mild kidney disease may appear healthy. However, dogs and cats with marked loss of kidney function can become very ill. The earliest symptoms of chronic kidney disease are as follows: Increased thirst (polydipsia) Increased urine volume (polyuria) These symptoms result from impairment of the kidneys ability to produce concentrated urine. Other common problems include the following: Weight loss Poor hair coat Increasingly selective appetite Further decline in kidney function results in progressive inability to eliminate waste products, leading to retention of toxic wastes in blood and tissue in the body. This condition is called uraemia (literally, urine in the blood). Prominent symptoms of uraemia include the following: Further loss of appetite Vomiting Ulcers in the mouth Uraemic (foul ammonia-smelling) breath Weakness Lethargy Other important effects of declining kidney function include anaemia (caused by inability of the kidneys to form erythropoietin, the hormone responsible for making red blood cells) and high blood pressure (hypertension). Anaemia worsens the weakness, lethargy, and loss of appetite of dogs and cats with advanced chronic kidney disease. High blood pressure may cause sudden blindness (due to retinal detachment) stroke-like signs (such as mental dullness, sudden behavioural changes, coma, or seizures), or cardiac problems. Page 2 of 5
What tests are needed? Diagnosis of chronic kidney disease is confirmed by laboratory evaluation of your pet s blood and urine: Urinalysis can help determine whether the kidneys can form concentrated urine and provide evidence of other urinary tract problems such as urinary tract infection. The more damaged a kidney is, the more dilute the urine becomes. Urine Bacterial Culture may be performed as a number of animals with kidney disease have secondary (or sometimes primary) bacterial infections which need antibiotic treatment. Blood tests used to evaluate kidney function include the Blood Urea Nitrogen (BUN) and Creatinine (CREA) concentrations. Because only the kidneys eliminate urea and creatinine from the body, increased urea and creatinine concentrations indicate decreased kidney function. These tests are usually performed together because they provide slightly different information. The serum creatinine concentration is the more specific test of kidney function, whereas BUN may reflect the effect of treatment and other factors. There is a new blood test that can be done to detect kidney disease much earlier in animals. This test (called the Renal SDMA test) can be done if early disease is suspected and will show changes before we see alterations in UREA/CREA values. Blood tests evaluating secondary parameters such as Phosphorus and Potassium imbalances that can occur with CRF. Haematology is useful as it will show whether any anaemia is present. Measuring blood pressure and the amount of protein in the urine is often performed because, left untreated, high blood pressure and too much protein in urine (proteinuria) can be associated with worsening of kidney function. Ultrasound (and occasionally x-rays) may also be used to evaluate kidney disease. Figure 1 - Urine "dipstick" test being performed. Figure 2 - Both of these kidneys felt normal on palpation and were exactly the same size. However the image on the left is a normal kidney, whereas the image on the right is severely abnormal. There were numerous fluid filled cysts present which was compromising the renal function. Page 3 of 5
What treatment is available? Depending on the stage of the disease, dogs and cats with chronic kidney disease can be treated, often providing a good quality of life for months or years. Treatment is tailored to the unique requirements of each pet but may include a kidney-friendly diet; hydration therapy; and medications designed to control symptoms (such as vomiting or poor appetite), acid-base and electrolyte complications, anaemia, proteinuria, and hypertension. 1. Dietary Control: Consumption of excess protein may make some pets ill because the waste products of protein metabolism are excreted by the kidneys and retained when kidney function is reduced. Dogs and cats with chronic kidney disease have been shown to live longer when fed kidneyfriendly diets. These diets are typically low in protein and phosphorus and also low in sodium and chloride (salt). Various prescriptions diets are available in both wet and dry form and so we hope to find a diet that your pet will still enjoy eating. Some animals may require potassium supplements too. We are now able to provide a sample pack of different types of food to see which ones your pet could be tempted to eat! 2. Good hydration: Careful control of water intake is very important. As the kidneys find it difficult to manage hydration in CRF. Although you will find that your pet is often drinking and urinating more, you must always let them drink what they want. Never restrict water. With cats you can sometimes help them hydrate properly with fluid injections under the skin. 3. Manage Blood Pressure: early detection and treatment of secondary hypertension (high blood pressure) will reduce the chance of sight loss and heart disease. 4. Manage anaemia: if your pet becomes anaemic, then this can sometimes be managed by using anabolic steroids and/or a blood transfusion. Figure 3 - A Feline Palatability pack to try your pet with different types and flavour of food. Figure 4 - Blood pressure being measured in a cat. 5. Manage secondary electrolyte problems: cats and dogs often suffer with low potassium and high phosphorus when suffering from CRF. A potassium supplement or phosphate binding agents (decrease amount of available phosphorus) can be given if necessary. 6. Direct Drug Treatment many cats (and in some situations some dogs) often respond to a class of drug called an ACE inhibitor. These drugs improve the blood flow to the kidney, often alleviating clinical signs. Given in tablet form, you cat will have to remain on this medication for life. Unfortunately there is no evidence of success in dogs and in fact can sometimes make matters worse. 7. Intravenous fluid therapy (IVFT) this basically involves putting the animal on a drip. This is a bit similar to dialysis in humans, in the sense that the extra fluids flush the system through and help reduce the amount of toxin build up. This will almost always make the animal feel better, and is often done in the early stages whilst other measures are being set up. It can be repeated on a regular basis providing the animal has good periods of life quality in between sessions. Regular follow-up examinations are important for successful treatment of dogs and cats with chronic kidney disease. Most pets should be examined on a regular schedule to evaluate for changes in kidney function and treatment needs. The tests performed each time will vary, but may include a blood test and possible blood pressure check. The frequency of these visits depends on the severity and type of kidney disease and the medications being used. Page 4 of 5
What is the prognosis after having been diagnosed with CRF? Unfortunately, Chronic Renal Failure cannot be cured; it can only be managed with varying degrees of success. The aim of treatment is twofold; firstly to try to slow down the rate of deterioration, and secondly to ensure a good quality of life for the pet, for as long as possible. So many different factors are involved; it is difficult to predict life expectancy. It is important to monitor the progression of the disease and treat the secondary problems (explained above) if/when they become apparent. Unfortunately towards the latter stages (so called end-stage renal failure) you may find that despite all attempts, your pet s quality of life is no longer acceptable. With these cases it is important to realise that euthanasia is often the kindest approach. For an animal to die naturally from CRF, they have often suffered a great deal towards the end stages of their disease. Page 5 of 5