Yes, they certainly can – although it isn’t as common as in cats, renal disease is seen in dogs.
What do the kidneys do?
A dog’s kidneys filter the blood and produce urine; overall, they have four basic functions:
- Controlling water and salt balance – by controlling how concentrated the urine is (more concentrated = less water is lost), and how much salt is reabsorbed from the urine into the blood before it is moved on down to the bladder.
- Getting rid of waste – the filtration means that wastes (like urea and creatinine) are removed from the blood, and other chemicals (like drugs or toxins) are excreted.
- Controlling blood pressure – firstly by controlling how much water there is in the body, but also by a complex cascade of chemical messengers called the renin-angiotensin-aldosterone system (RAAS) that controls both urine concentration and vasoconstriction (narrowing or widening of the blood vessels).
- Controlling red blood cell production – healthy kidneys produce a hormone called erythropoietin (or EPO for short) that tells the body to make red blood cells. If the kidney isn’t receiving enough oxygen in the blood, it makes more, to try and combat anaemia.
A dog can survive quite happily with only one kidney working – however, once there has been enough tissue damage that these functions are impaired, they are described as being in kidney failure.
What types of kidney failure do dogs get?
Dogs most commonly develop sudden onset kidney problems whereby large amounts of kidney tissue shut down – this is called acute renal failure (ARF). Sometimes it is relatively mild and they recover from it rapidly on their own. However, as damage mounts up, there is an increased risk that there will be permanent loss of function – this longer term condition is called chronic renal failure (CRF).
What causes kidney failure in dogs?
Cats develop CRF spontaneously, often without any obvious cause, but this is less common in dogs. In many cases, there will be a trigger incident that damages the kidneys (often causing ARF) and then they are left with permanent damage.
Typical causes include:
- Genetic defects (CRF is more common in certain breeds, such as the Samoyed, Bull Terrier and Cocker Spaniel).
- Dehydration, shock or abnormally low blood pressure for a prolonged time (after an injury, or occasionally in emergency surgeries such as for a torsion/GDV).
- Urinary obstruction (a blocked bladder, generally caused by a bladder stone).
- Toxins (such as antifreeze, and some drugs).
- Infection of the kidneys (pyelonephritis).
- Cancer of the kidneys (usually lymphoma, a cancer of the immune system).
- Some immune diseases which attack the kidneys (such as in Nephrotic Syndrome).
What are the symptoms?
Typically, symptoms usually start relatively minor and then worsen as toxins build up in the body. They may include:
- Altered urination:
- Usually reduced in ARF – the less urine is produced, the more severe thedamage and the worse the prognosis.
- ○ Generally increased in CRF and very mild ARF.
- Increased thirst.
- Depression and lethargy.
- Weight loss (usually only seen in CRF).
- Loss of appetite.
- Vomiting and, sometimes, diarrhoea.
- Bad breath (often, the breath smells metallic due to the presence of the waste chemical urea).
- Collapse, seizures, coma and death.
Those are quite vague – how do you tell if it’s the kidneys that are the problem?
The most common way to diagnose kidney failure is with blood tests – increased levels of waste products such as urea and creatinine indicate that the kidneys aren’t working properly.
Urine tests are also useful – healthy urine shouldn’t contain much protein, and should be well concentrated; the presence of high protein in urine with low concentration is a massive red flag!
Can it be treated?
Some of the underlying cause can be treated (such as primary dehydration, kidney infections, many toxins, and cancers like lymphoma). However, once CRF has developed, the condition has to be managed, not treated – the kidney tissue that has completely failed won’t grow back.
In ARF the priority is to maintain hydration and to force the kidney to produce some urine (even if it’s not very good at it), so we will admit affected dogs into the hospital and put them on a drip, and may give them diuretics to chemically stimulate urine production.
In CRF a drip may also be needed, but most often these dogs are managed with special diets (that are properly formulated to minimise the amount of work the kidneys have to do), drugs (such as ACE inhibitors), regular blood pressure monitoring, and free access to water.
If your dog seems unwell and isn’t urinating as expected, get them seen by one of our vets as soon as possible.