Acute Kidney Injury
What is acute kidney injury (AKI)?
The kidneys play a vital role in removing toxins from the body via filtration of the blood. Kidney failure implies that the kidneys are not successfully removing these toxins. ‘Acute’ kidney injury means that the problem has developed over a number of days rather than weeks/months.
There are many different causes of AKI. This includes poisons such as:
- Antifreeze (radiator fluid, ethylene glycol)
- Lily plants (cats only)
- Certain drugs, including pain pills such as aspirin or ibuprofen (Advil)
- Brunfelsia bush or tree (‘Yesterday, today and tomorrow’)
Severe infections in the kidney from bacteria can cause sudden kidney injury. In these cases, there is usually an underlying cause as to why your cat or dog cannot fight off infection (such as kidney stones or urinary blockages)
Leptospires are a group of bacteria that can cause acute kidney injury in dogs and cats. These bacteria are picked up by your pet consuming/licking or coming into contact with infected bodies of water (ie. A puddle containing rodent urine etc).
Anytime there is reduced blood flow to the kidney AKI can occur. Reduced blood flow can be due to: dehydration, heatstroke, disorders causing damage to blood vessels (snake bites).
What are the symptoms of AKI?
Initially you may notice excessive thirst or urination. Later in the course of disease clinical signs include: inappetence, vomiting or lethargy. Late in the course of disease clinical signs such as no urine production or black stools may be noted.
What tests are needed?
Blood and urine tests are used to determine if kidney injury is present, and if it is, how severe it is. Other tests include: ultrasound, xrays and additional specialised blood tests can be performed. In some cases, biopsy of the kidney may be indicated. The cause of kidney injury is not always easily discernible.
What treatment is available?
Initial treatment involves intravenous fluids to restore hydration and help flush tocins from the body. Urine production is monitored and diuretic medication may be given to help establish appropriate urination.
In addition to fluid treatment, other medications are commonly used. Antacids can be given to reduce the occurrence of stomach ulcers which occur with kidney disease. If ulcers are bleeding, medications to coat the ulcer may be prescribed. Antibiotics are given if the cause of the kidney failure is known or suspected to be infection.
Animals experiencing AKI often don’t want to eat so a feeding tube may be placed to assist nutrition.
Monitoring dogs and cats with AKI is very important. Checking parameters such as blood pressure, body weight, electrocardiogram and serial blood tests can help gauge how an animal is responding to treatment. Blood pressure can be elevated in AKI and may require medication to reduce the chances of serious side effects of hypertension.
An electrolyte called potassium can increase significantly with AKI, this can cause slowing of the heartbeat and in some cases causes the heart to stop beating.
Not all animals with acute kidney failure will respond to IV fluids. In these cases specialist referral may be required for advanced treatments such as dialysis. Indications for referral include: very high potassium levels, ongoing anuria (no urine production), fluid on the lungs or lack of improvement despite IV fluid therapy.
What is the prognosis?
Despite best efforts at present less than 40% of patients diagnosed with AKI survive. Dialysis is usually reserved for those patients in which medical treatment has failed and the chance of death without dialysis is almost 100%. In those patients, dialysis may allow up to half of them to recover, depending on the underlying cause of kidney failure.
Of the patients that survive some may have complete resolution of kidney damage whilst some will require ongoing care at home (such as lifelong medications and a specialised diet).
Chronic Kidney Disease (CKD)
What is chronic kidney disease or failure?
Kidney disease implies that there is either a structural or functional abnormality of one or both kidneys. It is often picked up when kidney function has declined enough to cause detectable changes on routine blood and urine tests.
The functions of the kidneys are the following:
- Eliminate waste products
- Maintain water and electrolyte balance
- Produce a variety of hormones
CKD means that the abnormality of the kidney/s 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 thousands of small functional units called nephrons. These filter the blood of toxins. 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. As a consequence, kidney disease can be an insidious condition that remains unrecognized either until blood and urine tests are performed or the patient becomes ill. CKD tends to progress over time.
The goal of managing chronic kidney disease is to try and diagnose the condition in its early stages so as to slow progression of the disease as much as possible.
What are the symptoms of chronic kidney disease?
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)
Other clinical signs include: weight loss, poor hair coat and picky eating.
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 uremia (meaning, urine in the blood).
Clinical signs of uremia include:
- Loss of appetite
- Ulcers in the mouth
- “Uremic” (foul ammonia-smelling) breath
Other side effects of declining kidney function include:
- anaemia (low red blood cells)
- high blood pressure
What tests are needed?
Diagnosis of chronic kidney disease is confirmed by laboratory evaluation of your pet’s blood and urine:
- Urinalysis to help determine whether the kidneys can form concentrated urine and provide evidence of other urinary tract problems such as urinary tract infection.
- Blood tests used to evaluate kidney function include the blood urea nitrogen (BUN) and creatinine concentrations. A newer blood tests called SDMA can be performed to help determine filtration rate of the kidneys.
- Measuring blood pressure and the amount of protein in 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 x-rays may also be used to evaluate kidney disease.
What treatment is available?
Fortunately, most dogs and cats with chronic kidney disease can be treated, providing a good quality of life for months or years.
Treatment options include: ‘kidney-friendly’ diets (that have reduced protein and phosphorus levels to reduce toxin build up in the blood), hydration therapy, medications to control poor appetite, anaemia, proteinuria and high blood pressure.
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 frequency of these visits depends on the severity and type of kidney disease and the medications being used.