Renal failure is the inability of the kidney to properly detoxify the blood of its nitrogenous waste. When we talk about renal failure in dogs or cats, there are 2 specific entities:
- acute renal failure
- chronic renal failure
Acute renal failure is a sudden and reversible deterioration of kidney function. It can affect dogs and cats of any age. Symptoms appear suddenly (thus “acutely”) and are often reversible if the cause of this failure is quickly treated. Its origin can be located at 3 levels:
- Upstream of the kidneys (we speak of a pre-renal cause), this is the case in particular when there is a blood circulation defect at the level of the kidneys (linked for example to dehydration, heart failure, haemorrhage…).
- At the level of the kidneys (renal cause). This is a direct attack on the kidneys, linked for example to a virus, a toxic product, an infection and/or inflammation of the kidney…
- Downstream from the kidneys (so-called post-renal cause). If the urine cannot flow normally, a retention can block and finally damage the kidneys. This is particularly the case when there is an obstruction due to a stone or a tumor.
Chronic renal failure in dogs and cats is due to a gradual and irreversible loss of kidney function. It is common in older animals and is a frequent cause of death in these animals. However, it can occur in younger dogs and cats. It is due to a direct alteration of the kidneys, secondary to a disease (chronic inflammation, chronic degeneration, renal tumor…), to a hereditary problem. It evolves over several months or years.
The symptoms of renal failure in dogs and cats
Acute renal failure:
The symptoms appear suddenly, they can be :
- fatigue
- loss of appetite
- vomiting/diarrhea
- altered breath (“green apple” smell due to ammonia)
- increased thirst (= polydipsia) and increased urine output (= polyuria)
In addition to these non-specific symptoms, there may be symptoms related to the cause of the acute renal failure in dogs and cats(urinary problems if stones, other symptoms related to a virus, intoxication, a heart problem…).
Chronic renal failure:
- increased thirst (= polydipsia) and increased urine output (= polyuria)
- vomiting
- loss of appetite / weight loss
- altered breath
The diagnosis of renal failure
Following the clinical examination and the collection of symptoms, the veterinarian will suspect a renal insufficiency.
To confirm it, he will perform laboratory tests following a blood test. The values classically measured are the urea and creatinine, it is their elevation which poses the diagnosis of renal failure in dogs and cats.
Other parameters can be measured (phosphate, red blood cells to look for anemia…). A urine analysis can also be done to look for the presence of proteins in the urine.
The veterinarian may also find it necessary, in some cases, to perform a renal ultrasound (+/- biopsy) to refine the diagnosis and prognosis.
Treatment of renal failure
Acute renal failure:
The damage to the kidney in acute renal failure in dogs and cats is normally reversible early in the course of the disease (it may become irreversible if treatment is delayed too long).
The treatment consists in restarting the kidney’s functioning with the help of perfusion, which will help the blood to eliminate nitrogenous waste. If the precise cause of this acute insufficiency is known, it can be treated, if possible (surgery to eliminate a stone, antidote if intoxication is identified, etc.).
At the same time, the diet should be adapted by providing the animal with a food containing a lower protein level and better quality proteins. The level of certain nutrients (such as phosphorus and sodium) must also be restricted in these foods.
Chronic renal failure:
In the case of chronic renal failure in dogs and cats, the damage to the kidneys is irreversible. Unfortunately it is not possible in Europe to perform a kidney transplant for our pets.
The therapeutic strategy will therefore be based on certain drugs that can reduce the work of the kidneys, slow down the degradation of the kidneys and reduce the clinical signs. A special “kidney” diet will have to be implemented (less proteins, better quality proteins, measured levels of phosphorus and sodium…).
Because degeneration is progressive, regular monitoring of kidney values is necessary (about 3-4 times a year). If symptoms are abundant and urea and creatinine values are high, hospitalization and infusions may be necessary.
The prognosis for the dog or cat
Acute renal failure:
If the origin of the renal failure in dogs and cats is toxic and the dog or cat is alive after 5 days, the prognosis will be quite favorable. Unfavorable factors for the prognosis are the age of the animal, the delay before the treatment is started, the presence of other concomitant diseases, a total or partial blockage of urine production.
Chronic renal failure:
The prognosis depends on the state of kidney damage at the time of diagnosis. If the kidney values are not too high or fall well after the initiation of treatment, the animal can live for several months or even years. If at the time of diagnosis the renal values of urea and creatinine are very high, the prognosis will be less good.
Conclusion
The follow-up of animals with renal insufficiency is essential, and should be carried out by the attending veterinarian who will monitor the renal parameters by means of blood tests.
From a certain age, veterinarians often propose a geriatric follow-up of the animal, this follow-up generally includes the measurement of urea and creatinine to check the renal function. It is therefore wise to accept these geriatric check-ups, because if renal insufficiency is detected early, a special diet can be put in place to increase the life expectancy of the dog or cat.