chronic Kidney failure in cats What is chronic kidney failure?
Chronic kidney failure, or chronic kidney disease as is it otherwise known, refers to an irreversible and progressive disease of the kidneys that leads to them not being able to perform their regular function.
How does chronic kidney failure occur?
The kidneys are made up of many functional units called nephrons. Each one of these nephrons performs a multitude of functions that are responsible for excreting waste products from the body, regulating electrolytes, regulating blood pressure and producing red blood cells in the body. The kidneys have what we refer to as a large reserve capacity, meaning that the kidneys can continue to perform their necessary functions despite the loss of many of these nephrons. In fact, the kidneys can continue to perform their necessary functions until approximately 75% of the nephrons have been lost. This means that over a lifetime, many repeated injuries can occur to the kidneys which can damage a number of the nephrons, which ultimately leads to the kidney losing enough of its functional capacity to cause chronic renal failure. Once a certain percentage of the nephrons have been lost, it incites a vicious cycle leading to further destruction of nephrons. Some animals may be predisposed to developing chronic kidney failure as a result of birth defects which lead to them having less functional nephrons to start with. Other types of injuries to the kidneys include kidney infections, kidney stones, bladder stones that occlude the flow of urine from the kidneys to the bladder, urinary tract obstructions as a result of crystals or cells that cause a blockage in the urethra (most commonly seen in male cats), prior acute kidney injuries that can occur as a result of toxin exposure, autoimmune damage directed at the kidneys, cancer in the kidneys or any condition in
which severe dehydration occurs. In the vast majority of cases, by the time chronic kidney failure has been identified, the inciting causes are no longer present or cannot be identified.
What are the symptoms of chronic kidney failure?
The kidneys have a multitude of functions within the body, therefore there are a large number of clinical signs that can be observed. Most often, one of the first functions that the kidneys lose is their ability to adequately concentrate the urine. This leads to a pet urinating in large volumes. To compensate for this, animals will start drinking increasing amounts of water to compensate for this loss. At the same time, the kidneys will usually also start losing their ability to remove proteins from the urine that should stay in the body. This loss of proteins through the urine then leads to weight loss. During this time, your pet may not necessarily feel unwell, but, as the disease progresses, further loss of function leads to other symptoms that make them feel sick (usually nauseous). The most notable of these is what we refer to as azotaemia, which is a word that describes the build-up of nitrogenous waste products formed during protein metabolism in the body. In particular, we use the term azotaemia to refer to urea and creatinine. These waste products will make your pet feel ill if they are not excreted efficiently from the body. This can make your pet unwilling to eat and may also cause vomiting. Veterinarians monitor creatinine levels to gauge the progression of the
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kidney disease in a specific animal. These elevated levels of urea and creatinine can lead to inflammation in the stomach (referred to as uraemic gastritis), as well as halitosis (a particular bad smell coming from the mouth) and ulcers forming in the mouth and stomach. The kidneys are also responsible for regulating electrolytes within the body, and loss of the correct balance of electrolytes in the body can make your pet feel even more sick and weak. If your pet is not eating and drinking enough, because they feel ill, this will lead to dehydration, which compounds the azotaemia and makes them feel even worse. If the kidneys start losing their ability to function correctly, a process is triggered in the body that leads to the pet developing high blood pressure, which further damages the kidneys. The kidneys are also responsible for producing a hormone called erythropoietin, which is the stimulus for the production of red blood cells in the bone marrow. Chronic kidney disease will lead to decreased levels of erythropoietin which will lead to a decreased production of red blood cells in the body, resulting in anaemia which will leave your pet feeling weak. The ability of the kidneys to concentrate urine is one of the defence mechanisms of the body that help to prevent the bladder from becoming infected with bacteria. As cats with chronic kidney failure have poorly concentrated urine, they are very prone to bacterial bladder infections.
MARCH 2022 | PETPRINTS
