Kidney Failure in Dogs

The kidneys are a vitally important organ — through their many functions, they help maintain homeostasis in the body (a stable state of balance). When their function is disrupted, dogs develop a medical problem known as kidney failure.

If you suspect your dog might have this problem, or even if they've already been diagnosed, this information will be very useful. Let's take a detailed look at everything related to canine kidney failure.

How does kidney disease develop in dogs?

The kidneys are the main organs of the urinary system and carry out essential functions for our dogs' lives:

1. They filter the blood, excreting metabolic waste and toxins produced by the dog's body (urea, ammonia, uric acid, and creatinine) through urine.
2. They regulate and maintain plasma volume by diluting or concentrating urine.
3. They play a role in regulating blood pressure and keep blood pH stable through acid-base regulation mechanisms.
4. They have an important endocrine role, secreting certain hormones involved in red blood cell production.

When something fails in this system, compensation mechanisms kick in that can keep it working. The downside of this compensation is that, in many cases, dogs are diagnosed once the disease is already quite advanced.

We only speak of kidney failure once at least 3/4 of the functional capacity of the nephrons in both kidneys is impaired — that is, when 75% of the nephrons are no longer functional. There can be cases of impairment without damage, or minor damage that doesn't reach the point of failure, so it's important to make this distinction.

Canine kidney failure can present in two ways, as we'll see below.

Acute kidney failure in dogs

Kidney failure in our dog can appear suddenly, over a few hours to 1-2 days. This type of failure can be of several kinds: prerenal, if caused by underlying issues such as reduced cardiac output, low blood volume, or clotting; renal, from infectious, parasitic, or toxic causes; and postrenal, generally from an obstruction.

Cases of acute failure are a life-threatening emergency and require immediate veterinary care. They're potentially reversible, and the dog may recover with no lasting effects, but if significant kidney damage has occurred, it could be irreversible, turning into chronic kidney disease.

Chronic kidney failure in dogs

This type of kidney failure involves a slow, progressive loss of kidney function (over months or years). It's the most common presentation, more frequent in older dogs, but we won't notice symptoms until the damage is already advanced.

This is why annual vet check-ups are so important, especially for dogs over 7 years old, since early diagnosis helps maintain quality of life. This type of failure can be caused by congenital diseases such as polycystic kidney disease or renal dysplasia, or by diseases acquired over our dogs' lifetime, such as infections, tumors, hydronephrosis (water buildup in the nephron from bladder obstruction), amyloidosis (buildup of amyloid substance in the kidney), and so on.

The structural or functional changes caused, such as possible sclerosis and fibrosis of the compensating nephrons, are irreversible in this case.

Symptoms of kidney failure in dogs

Although these can vary depending on whether it's an acute or chronic process, the most characteristic symptoms of kidney failure in a dog are:

• Polyuria, meaning an increase in urine output, which will be clear and less concentrated. In acute cases, the opposite can happen — anuria, the inability to produce urine, which is an emergency.
• Polydipsia, since to compensate for the large amount of urine lost, the dog drinks more.
• Weight loss, poor body condition, and a poor-looking coat and skin, only in chronic cases.
• Dehydration from fluid loss. This imbalance can cause swelling (edema).
• Vomiting and digestive discomfort, along with ammonia-smelling breath and even mouth sores, due to the rise in uremic toxins in the blood, which stimulate the vomiting center and produce that very characteristic smell.
• Lethargic behavior and pale mucous membranes from anemia — hematocrit will be reduced as a result of decreased erythropoietin production.

In the most severe cases, the dog could go into a coma, which is why it's so important to see a vet as soon as we notice any of these symptoms.

Kidney failure can be diagnosed through a urine and blood test, which will show elevated values such as creatinine and urea (azotemia), phosphorus (hyperphosphatemia), and/or potassium (hyperkalemia). Tests such as blood pressure measurement, X-rays, or ultrasound may also be done.

How to treat canine kidney failure

First, we need to know what type of kidney disease we're dealing with, since if it's a prerenal or postrenal condition, we'll need to treat the underlying cause. If it's purely renal, however, treatment for kidney failure in dogs differs depending on whether it's acute or chronic:

1. Acute kidney failure: as mentioned, this is a veterinary emergency that will require hospitalization for fluid therapy. Depending on the cause, treatment can range from surgery — for example, in the case of a ruptured bladder — to medications to control the various symptoms, such as anti-nausea drugs for vomiting, stomach protectants, and so on. Prognosis is guarded, but with early, appropriate treatment it can be reversible.
2. Chronic kidney failure: treatment will be palliative, since in this case the damage is irreversible, so it's based on controlling symptoms, for which various medications can be given. Based on clinical findings and test results, the vet will tell us which of the four stages of kidney disease our dog is in, based on severity, which will determine what medication is needed.

What's more, food specifically formulated for dogs with kidney failure is essential, with food based on natural ingredients being the most recommended. This disease can't be cured, but with these measures we can try to maintain a good quality of life for as long as possible.

What is life like for a dog with kidney failure?

A dog with this disease needs specialized food that eases the kidneys' workload and helps protect them. On the market you'll find various kibble and wet food options. These animals need a diet rich in highly digestible, high-biological-value protein to make up for proteinuria, the loss of protein through urine.

It's also necessary to control the levels of certain minerals like phosphorus, which can worsen damage to the kidney tubules and speed up the process. If the dog refuses their food, it's important to keep trying different options until you find one they'll eat, since it's essential that they eat and don't go with an empty stomach, as this would worsen their condition.

It's also essential to have fresh water available at all times, to follow the medication schedule the vet has prescribed, and to contact them about any symptoms. With these precautions, a dog with kidney failure can lead a completely normal life.