Immune-Mediated Hemolytic Anemia In Dogs

IMHA (Immune Mediated Hemolytic Anemia) is a serious medical condition that impacts dogs and cats alike.

Immune mediated hemolytic anemia involves the body attacking its own red blood cells, resulting in an array of severe complications for the dog affected.

So what is IMHA in dogs, and what does this diagnosis mean for your canine companion?

In this article we will aim to describe this complicated condition in our canine friends, and help you better understand the treatment options available to your pup.

Immune-Mediated Hemolytic Anemia In Dogs

Understanding Anemia In Dogs

Before we discuss the details of IMHA (immune mediated hemolytic anemia), it’s important to first understand what anemia is in the first place.

The term anemia refers to a reduced number of red blood cells circulating within the body, as well as the potential for reduced hemoglobin levels as well.

In a healthy dog free of anemia, their red blood cells will go through a standard life process.

The red blood cells are produced within the bone marrow, circulate in the bloodstream for about 3 months, and will be removed naturally when they break down or become damaged.

This cycle will repeat itself over and over, resulting in a steady flow of red blood cell production.

When a dog has anemia for any reason, this life process is interrupted.

Something leads to a destruction of red blood cells in the bloodstream, resulting in a dropping PCV (packed cell volume).

Red blood cells, and the hemoglobin within these cells, are responsible for the transport of oxygen throughout the body.

This is what makes anemia a life threatening condition.

What Is IMHA In Dogs?

Just like any other immune mediated condition, the body will begin to attack itself in some form.

IMHA involves the dog’s body destroying its own circulating red blood cells, resulting in dangerous and sudden anemia.

These red blood cells are still being produced within the bone marrow, but experience a shortened lifespan when entering circulation.

This leads to a dangerously low PCV, typically worsening until the dog receives aggressive medical care.

What Causes IMHA In Dogs?

Though IMHA has been around for quite some time, we still do not fully understand the condition and its main trigger.

While some cases of IMHA seem to develop without an explanation, others appear to be a result of underlying illness or a triggered immune response.

When discussing the cause of IMHA with your veterinarian, they will likely refer to your pup having either primary or secondary IMHA.

Primary IMHA

Primary IMHA is thought to make up about 75% of all IMHA cases in dogs.

Primary IMHA refers to a case of IMHA that occurs without a known cause, or when no underlying medical cause can be found.

Your vet may also refer to this form as idiopathic, meaning they cannot find a concrete cause of your pup’s current condition.

Secondary IMHA

Secondary IMHA refers to a case of IMHA that develops as a result of something else.

This means your pup’s IMHA may have been triggered by a previous or current illness, toxicity, cancer, current infection, or any other condition that triggers an immune response in some form.

Stressful events within your dog’s body can cause their immune system to “overreact”, resulting in a sudden and dangerous flare up that can lead to IMHA.

In most cases, you may never know what caused your dog’s current IMHA.

This is what makes the condition so difficult for both pet parents and veterinary professionals to understand, making it one of the more challenging conditions to treat effectively.

Symptoms Of IMHA In Dogs

The symptoms of IMHA in dogs are often startling, resulting in an immediate trip to the vet when pet parents first observe them.

Early detection of IMHA in dogs is essential for offering your dog a chance at recovery, making it important to be aware of the potential signs and symptoms to look out for.

Some of the most common symptoms of IMHA in dogs include:

  • Extreme lethargy or weakness
  • Pale gums
  • Changes in normal respiratory rate
  • Increased respiratory effort
  • Loss of appetite
  • Quick to tire out with exertion
  • Vomiting
  • Red or brown urine
  • Jaundice mucous membranes
  • Collapse

If you notice any of the above symptoms in your canine companion, it’s best to immediately contact your veterinarian.

Even if your pup’s symptoms are not due to IMHA, they can be a result of other serious complications.

Diagnosing IMHA In Dogs

If your veterinarian is suspicious of IMHA in your dog, there are a few diagnostic tools they may turn to.

First, your vet will likely perform a full panel of blood work, searching specifically for a CBC (complete blood count) and any elevated enzymes in the kidney or liver.

While the CBC is most important for testing the values within the blood, testing the function of the kidneys or liver can be beneficial when trying to determine any possible causes of the IMHA.

Next, your veterinarian will likely perform a PCV (packed cell volume) and a blood smear.

The PCV will measure the percentage of blood cells within the sample, while the blood smear will examine the appearance of the red blood cells under a microscope.

Both tools are important when diagnosing IMHA, as this can offer a clear picture of the severity of anemia present, and search for any evidence of regeneration of the blood cells.

The next manual tool that is extremely helpful in diagnosing IMHA is a slide autoagglutination test.

This searches for any abnormal clumping of the red blood cells, helping to further point to the likelihood of IMHA versus other medical conditions.

While this test is extremely simple, it can offer wonderful insight.

This test involves placing a single drop of EDTA-anticoagulated blood on a microscope slide, mixed with a couple drops of saline.

When rocking the slide back and forth, the tester can search for any evidence of abnormal clotting.

Once your veterinarian has diagnosed IMHA in your dog, they will then begin the hunt for any potential cause of their condition.

Your vet may suggest different diagnostics based on your dog’s medical history, so this can vary from case to case.

Can You Treat IMHA In Dogs?

While you can treat IMHA in dogs, the process can be quite lengthy and complicated.

The treatment process will often vary based on the cause of your dog’s IMHA, and may even require the care of an internal medicine specialist if the case is more complex.

First, if your dog’s anemia is life-threatening, your vet will likely suggest an immediate blood transfusion to restore their red blood cell count.

This will be performed by first blood typing your canine friend, and stabilizing them with a blood transfusion from an adequate donor.

This may be with packed red blood cells that your vet already has on hand, or with blood from a suitable canine donor at that moment.

If there is a known cause of your dog’s IMHA, your vet will need to treat the underlying condition before moving forward.

For example, if your dog’s IMHA is a result of an immune response to a current tick disease, your dog will be unable to fully recover until the underlying condition is resolved.

If your dog’s IMHA is primary or idiopathic, they will often move forward with immunosuppressive therapy.

The standard treatment plan will vary based on your dog’s situation and your vet’s treatment preference, ranging from a combination of immunosuppressive medications to high doses of steroids.

It’s important to realize that IMHA treatment is not a one size fits all approach.

Cases can vary greatly from dog to dog, with many dogs requiring several months of treatment therapy from the point of diagnosis.

If your dog is diagnosed with IMHA, be ready to have a close relationship with your veterinarian going forward.

Is IMHA Fatal In Dogs?

Unfortunately, IMHA in dogs is considered a potentially fatal condition.

Recovery often varies based on how severe the case is, the cause of their IMHA, and whether or not a dog receives adequate treatment.

IMHA also has a high likelihood of relapse in the future, making it a disease that can wait over your dog’s shoulder, even after they initially recover.

The best chance at recovery for your dog is achieved by following your vet’s recommendations during initial treatment and in the future.

The fatality rate of IMHA in dogs ranges from 30-70% based on the underlying cause, making it a complex condition that requires close attention going forward.

What To Keep In Mind For The Future

Not only is IMHA a frightening condition as your pup is experiencing it, but the chances of relapse in the future are high.

Dogs can experience an IMHA relapse anywhere from weeks to months after their initial diagnosis, making it a tough condition to predict.

The chance of relapse makes it extremely important to not only monitor your pup each day for any sign of illness, but to also maintain a close relationship with your veterinarian.

We suggest keeping up with any ongoing treatment or diagnostics that your veterinarian suggests, and always seeking advice before modifying any aspects of your dog’s care.

It’s also important to disclose your dog’s history with IMHA if you ever switch to a new veterinarian.

Their history with IMHA may alter any future treatment methods if your pup requires future medical care.

Even if it is something as simple as their yearly vaccines, you should always inform any new veterinary professionals in your dog’s life.

Final Thoughts

IMHA is a complex condition that can leave you with a long list of questions.

Be sure to review the information that we discussed above, and you can better understand your dog’s IMHA going forward.

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