What is Pulmonary Fibrosis in Dogs?

Fibrosis is a general term for the formation of excess fibrous tissue in the body, whether on an organ or any type of bodily tissue. Sometimes this is healthy as it can be used to repair damaged tissue. However, it can also be pathological, especially if it is as a result of a disease or injury. Scarring is a type of fibrosis and lung scarring is referred to as pulmonary fibrosis (pulmonary meaning it refers to the lungs).

The causes of pulmonary fibrosis are varied and not always known. It is a serious condition and can drastically reduce the quality of life of the animal as it compromises breathing. Some dog breeds are more susceptible than others. The West Highland White Terrier or Westie is perhaps the breed most associated with pulmonary fibrosis. The prevalence in this breed has been published in numerous journals.

As we stated in the introduction, symptoms of pulmonary fibrosis in dogs can be confused with other respiratory diseases. Generally, dogs affected by this clinical problem will have the following observable symptoms:

• Persistent chronic coughing
• Tachypnea (abnormally rapid breathing)
• Cyanosis (discoloration of mucus membranes)
• Intolerance to exercise
• Syncopes (fainting)

All these symptoms are also characteristic of cardiac pathologies (heart problems), but complementary tests must be performed to reach the correct diagnosis.

The causes of pulmonary fibrosis in dogs are relatively poorly known in the scientific community. It is a pathology which is still being studied closely and there are certain theories which provide suggestions for its possible origins. They include:

• Inadequate environmental control: dogs which have constant exposure to dust, harmful substances and respiratory irritants, may be more prone to lung fibrosis.
• Chronic respiratory infections: some dogs may have relatively mild respiratory infections which are recurrent. When they are chronic or not treated correctly, the damage can become cumulative and result in pulmonary fibrosis. This will usually occur later in life.
• Genetics: as Westies have a predilection for the condition (as do Terrier breeds in general), this suggests there may be a genetic factor influencing its development. However, it is important to note any breed or mongrel dog can have the disease.
• Cancer in dogs: it has been possible to show that some dogs with pulmonary cysts can develop this pathology throughout their life. Abnormal cell growth can lead to an over-accumulation of fibrous tissue.
• Inhaling noxious gas: while it is unlikely your dog will be around very noxious gas, inhaling toxic substances can cause your dog's lungs to scar.

Pulmonary fibrosis without apparent cause is known as idiopathic pulmonary fibrosis in dogs. This is the case in the majority of clinical examples, especially since determining the cause doesn't necessarily affect the treatment plan.

Before we discuss possible treatment for pulmonary fibrosis in dogs, we need to be clear that this is a chronic condition which usually develops over time. Treatment can be carried out in the form of symptom management, but it is practically impossible to reverse. Most authors report that there are drugs which can relieve the associated symptoms, but the dog is unlikely to return to full health.

To establish a treatment plan which improves the symptomatology of the animal and help to extend their life, we need to first achieve a correct diagnosis. Investigating the health of the respiratory and cardiovascular system is not always easy. Certain diagnostic tests can be performed by a veterinarian who suspects pulmonary fibrosis, including:

• X-ray: radiology is the most important diagnostic test for pulmonary fibrosis in dogs. The characteristic fibrous tissue is visible on x-rays if you know what to look for, which is the veterinarian's responsibility. In some cases, the x-rays taken may be used as reference for cystic pulmonary fibrosis. This is particularly important when there is a possibility of cancer cells being present.
• Hematology: the dog's blood chemistry will be an indicator of disease, but it is not the most accurate diagnostic test when it comes to an accurate diagnosis of pulmonary fibrosis. However, it is a vital test since it will be able to tell us if there are certain other diseases or if there are complications relating to their health. If pulmonary fibrosis is present, there should be an increased in red blood cells due to hypoxia (inadequate oxygen supply).
• Echocardiography: a significant percentage of dogs with pulmonary fibrosis present with pulmonary hypertension, a clinical sign which needs to be diagnosed via this method. In recent studies, more than 40% of the West Highland Terriers examined were diagnosed with pulmonary hypertension alongside lung fibrosis.

There are other other techniques used to differentiate a pulmonary fibrosis diagnosis with a related condition such as bronchitis or bronchoalveolar lavage (BAL). Since they are invasive techniques which require specific equipment and a veterinary specialist, they are less commonly used. Additionally, they can provide greater risk to the dog's well-being.

All of the diagnostic methods mentioned above will only be carried out after an initial physical examination. Under no circumstances should the dog be put through uncomfortable or painful procedures if not strictly necessary.

Treatment of idiopathic pulmonary fibrosis is based on the symptoms displayed by an individual dog, as well as their clinical picture and medical history. If the patient has pulmonary hypertension, the first thing the veterinarian will need to do is get it under control. This therapy is not curative, but it can help to retard the progression of the disease.

Steroid and antitussive (cough suppressant) medicines have been used to relieve symptoms. However, we reiterate this is not a cure. Environmental management is also very important. Any dust, harmful chemicals or other possible irritants need to be removed from where the dog spends their time.

As mentioned earlier, we are discussing a chronic pathology which is often idiopathic. A few authors of related studies have plotted a timeline of dogs with this condition. They suggest dogs which have been diagnosed with the condition can survive between 16 and 30 months after the onset of clinical signs. It is possible the life expectancy of the dog can be a matter of years. However, due to the relationship between the lungs and other vital organs, it is possible they will only last months after diagnosis.

It should also be taken into account that pulmonary fibrosis is a disease which is rarely diagnosed in younger dogs. Trying to estimate how long the dog will survive with pulmonary fibrosis is difficult to determine. Since senior dogs are normally affected, they will be more vulnerable to weakening.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to What is Pulmonary Fibrosis in Dogs?, we recommend you visit our Breathing diseases category.