Idiopathic pulmonary fibrosis in the dog and cat

Presenter: Professor Brendan Corcoran MVB DipPharm PhD MRCVS Personal Chair in Veterinary Cardiopulmonary Medicine. Royal (Dick) School of Veterinary Studies

West Highland White Terriers (WHWT) in their ‘twilight’ years presenting with a cough and crackles on thoracic auscultation are surely only suffering from one condition, Idiopathic Pulmonary Fibrosis IPF. According to Professor Brendan Corcoran, who led last week’s webinar covering IPF, I’m surprisingly not too far off the mark.

Of course, we all know that diagnosis is generally never quite so straight forward and in the case of IPF it is important to rule out other differential diagnoses. History and signalment play a key role in diagnosing IPF with WHWTs being the stand out predisposed breed, although Professor Corcoran has seen a small number of cases in both the Cairn Terrier and Staffordshire Bull Terrier. IPF is a slowly progressive disease seen in older animals with a median age of 9 years old. Clinical signs include coughing, dyspnoea and exercise intolerance although patients remain healthy and active.

The gold standard for diagnosing IPF in humans is High Resolution Computer Tomography (HRCT) and this is also the case in dogs. HRCT is obviously fine for owners who are insured or willing to pay the price for accessing the necessary equipment and expertise but HRCT may not be a viable option in every case. A diagnosis then has to be made based on history, signalment, clinical signs and the results of diagnostics which help to rule out other conditions. Radiography is an excellent starting point and changes associated with IPF on thoracic X-rays can vary from subtle changes through to the presence of such diffuse interstitial pattern, it is difficult to imagine how this animal is still alive. Bronchoalveolar lavage (BAL) should also be performed which, in Professor Corcoran’s experience, is often acellular in cases of IPF.  Bronchoscopy is also useful in ruling out conditions such as chronic bronchitis which can be mistaken for IPF.

The million dollar question most vets have about IPF is how to treat this condition, and unfortunately Professor Corcoran explained the prognosis for these patients is poor, with a median survival time of between 1-36 months post presentation and there is little available evidence for any definitive pharmacological benefit. Professor Corcoran did explain however that there is reasonable confidence that treatments including colchicine, mono therapy corticosteroids and interferon have NO clinical benefit. If improvements are seen with treatments such as steroids, it may be because the patient has other concurrent conditions such as chronic bronchitis or the IPF diagnosis is incorrect. Drugs which may be of benefit include slidenafil (Viagra) and pimobendan and are aimed at treating pulmonary arterial hypertension which develops as a consequence of IPF. A new drug called perfenidone is also now available for humans and is showing evidence of benefit but is currently not available to the veterinary market.

Professor Corcoran’s expanse of knowledge and passion for IPF shone through this webinar. Dogs were not the only species on the agenda with Professor Corcoran delivering a mass of information on cats and humans. Interestingly cats suffering with IPF tend to have similar pathology to humans, and as with humans, may have coexisting lung carcinomas. For more practical and up to date advice on the diagnosis and management of IPF both in dogs and cats, logging into Professor Corcoran’s webinar is an excellent place to start.

The Stethoscope (MRCVS)

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