Kidney failure stages in dogs are four and they are based on the progression of the disease. Previously, there was little clarity on the staging of kidney failure in dogs and there were no uniform definitions of what comprised early kidney disease or end stage kidney disease. Nowadays, the International Renal Interest Society (IRIS) has formulated a staging system that can help veterinarian and dog owners better understand and treat chronic kidney failure in dogs. Following is some information on the four kidney failure in dogs.
A Closer Insight
To better understand kidney failure stages in dogs, it helps to first gain a better understanding of what happens in dogs when they develop chronic kidney failure.
In healthy dogs with healthy functioning kidneys, the kidneys work relentlessly, around the clock, filtering the blood and removing any metabolic waste products which are then excreted through the urine. As dogs age though, wear and tear starts taking its toll affecting the kidneys which have been working for many years.
When the kidneys stop working as they should, several complications start setting in. Metabolic waste products are no longer removed as they should and these toxins start accumulating in the dog's body. The body, being a wonderful machine that has an innate desire to repair itself, will attempt to flush out these toxins by eliciting the dog to start drinking and urinating more.
While increased drinking may help, it can only do so up to a certain extent. Toxins will keep accumulating and the condition will progress causing affected dogs to develop more symptoms such as loss of appetite, vomiting, diarrhea, lethargy, ulcers in the dog's mouth and bad breath.
Because the kidneys are no longer working as they should and toxins are no longer effectively excreted, the urine is no longer concentrated and tests will show a a low urine specific gravity. The dog's bloodwork will also show abnormalities in the blood urea nitrogen (BUN), serum creatinine (CREA) and in the levels of potassium, phosphorus and calcium.
The Four Stages of Kidney Failure
The International Renal Interest Society (IRIS) is an organization that is dedicated to advance the scientific understanding of renal diseases affecting small animals. This society is led by fifteen reputable veterinarians with a special interest in the branch of medicine that deals with diseases of the kidneys.
The mission of IRIS is to establish a set of guidelines that aim to improve how this disease is diagnosed and treated. In order to better help understand kidney disease, IRIS has created a four-stage system for kidney disease affecting cats and dogs.
Several dogs are considered at risk for developing chronic kidney disease either because they have a history of being exposed to drugs that are toxic to the kidneys or because they are particularly predisposed to this disease because of age, breed or living in a location with a high percentage of infection diseases. Such dogs require close monitoring.
The classification of kidney failure stages in dogs is mostly based on the dog's serum creatinine concentrations and what the urine specific gravity is.
Stage 1 Kidney Disease
Kidneys are responsible for removing waste products from the dog's body. When kidney function is impaired, waste products accumulate in the blood, causing what is known as "uremic poisoning." In particular, the collection of nitrogen-containing compounds in the blood is known as "azotemia."
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In dogs with stage 1 chronic kidney disease, there is no accumulation of abnormally large amounts of nitrogenous waste products in the dog's blood. Dogs at this stage are therefore claimed to be non-azotemic.
However, diagnostic tests have found that dogs at stage one have some abnormalities such as inadequate urine concentration, abnormal tissue biopsy results or the kidneys appear abnormal upon palpation or though diagnostic imaging.
Further diagnostic tests may reveal presence of excess protein in the dog's urine or increasing levels of creatinine concentrations (less than 1.4 mg/dl) when the samples are collected in series. Typically no symptoms are seen at this stage.
Stage 2 Kidney Disease
In stage two kidney disease, renal lesions progress and the dog's renal function deteriorates. Affected dogs show mild nitrogenous waste products in their blood. Their creatinine concentration at this stage will range between 1.4 and 2.0 mg/dl.
Creatinine is simply a nitrogenous waste molecule that is produced by muscular activity. This waste product is normally eliminated through a dog's kidneys, therefore higher than normal concentrations are indicative of kidney disease.
At this stage, the affected dog may be showing only mild symptoms of kidney disease, but some dogs may even show none.
Stage 3 Kidney Disease
In level three kidney disease, affected dogs show moderate nitrogenous waste products in their blood. Their creatinine concentration at this stage will range between 2.1 and 5.0 mg/dl.
Affected dogs may show several signs of disease such as increased drinking and increased urination and perhaps some loss of appetite. At this stage, the kidneys are likely functioning only between 15 and 25 percent.
Stage 4 Kidney Disease
In level four kidney disease, creatinine levels are greater than 5.0 mg/dl. At this end stage of canine kidney failure, the dog is at risk for developing systemic signs affecting the whole body and may develop uremic crisis, which takes place when the dog's body can no longer filter body waste through the kidneys.
Affected dogs show significant signs of disease and may require hospitalization. At this stage, the kidneys are likely functioning only under 15 percent.
- DVM360: Staging and Management of Chronic Kidney Disease Proceedings
- Dvm360: 5 Key Steps For Managing Chronic Kidney Disease