Page 318 - WSAVA2018
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 25-28 September, 2018 | Singapore
WSV18-0110
DIAGNOSTIC IMAGING
IS IT THE HEART OR THE LUNG? - THORACIC RADIOGRAPHY IN THE COUGHING DOG
G. Seiler1
1North Carolina State University, Molecular Biomedical Sciences, Raleigh, USA
IS IT THE HEART OR THE LUNG? THORACIC RADIOGRAPHY IN THE COUGHING DOG
Gabriela S. Seiler DECVDI, DACVR
College of Veterinary Medicine, North Carolina State University, 1052 William Moore Drive, Raleigh, NC 27607, USA. gsseiler@nscu.edu
Introduction
Thoracic radiographs are the imaging method of choice in the coughing or dyspneic dog or cat, but abnormalities of the pulmonary parenchyma are inherently difficult to interpret due to the overlap in radiographic appearance of different diseases. The question of heart vs. lung disease is a common one in patients with clinical signs
of cough or dyspnea and in the following we will go over some interpretation criteria that help with this decision.
Importantly, even though we will mostly talk about thoracic radiographs in this presentation, radiographic findings have to be interpreted in light of clinical findings. Abnormalities in heart rate, heart rhythm and presence of a heart murmur are important information to take into account. It is equally important to assess clinical findings over the course of the disease and after treatment has been initiated based on the primary differential diagnosis to determine if adequate treatment response is present.
Radiographic findings of heart disease
Radiographic findings that point to heart disease as the primary cause of cough or dyspnea in a dog include changes in the cardiac silhouette, pulmonary vasculature and pulmonary parenchyma. Cough and dyspnea is caused by left sided heart disease or heart dysfunction. Increased size of the left heart results in a taller cardiac silhouette. In a lateral radiograph this usually results in dorsal displacement of the trachea. In a ventrodorsal (VD) or dorsoventral (DV) projection the cardiac silhouette may be elongated as well but could also have a rounded appearance only if the dog is deep chested and the heart is in a very upright position. Left atrial enlargement results in a convex bulge in the caudodorsal contour of the cardiac silhouette in the lateral views. The main stem bronchi are splayed in the VD or DV projections and there may be a bulge visible in the left lateral aspect of the contour of the cardiac silhouette approximately at 2-3 O’clock. Dorsal deviation of the main stem bronchi
by an enlarged left atrium may result in bronchial compression and cough, particularly if a component of bronchomalacia and bronchial collapse is present. Left atrial enlargement is typically pronounced in dogs in
left sided congestive heart failure and a lack of left atrial enlargement should prompt the clinician interpreting the radiograph to consider other causes for the cough.
Evaluation of the pulmonary vasculature should always go hand in hand with evaluation of the cardiac silhouette. It is especially important in dogs with cough or dyspnea where left-sided congestive heart failure is considered. In presence of left heart failure there is volume overload of the left atrium and subsequent congestion of the pulmonary veins trying to return the blood volume from the pulmonary circulation into the heart. Enlargement
of the pulmonary veins is therefore an excellent radiographic sign of left heart dysfunction. Pulmonary venous dilation, however, may not be present if a patient has been treated with diuretics prior to obtaining the radiographs. Additionally, very mild pulmonary venous dilation may be difficult to recognize radiographically so a lack of pulmonary venous dilation should not be used to completely rule out heart failure.
Lastly, there are pulmonary changes associated with
left sided congestive heart failure. Cardiogenic edema transitions from the interstitial space to the alveolar space and therefore has the potential to create variations of pulmonary patterns. Once there is pulmonary venous congestion with associated pressure increase in the vessels, fluid may be leaking into the interstitial space around the vessels. The lymphatics initially compensate by increased drainage of the interstitial space but ultimately may become overwhelmed, resulting in fluid buildup in the interstitial space. The interstitial fluid will cause opening of the tight junctions between alveolar wall cells and fluid will flow into the alveolar space. It therefore makes sense that pulmonary patterns can
vary from interstitial to alveolar, depending on the stage of the disease. To make things more complicated the cardiogenic interstitial edema is present around the bronchial walls as well which can give the appearance of a peri-bronchial infiltrate and a radiographic bronchial or bronchointerestitial pattern. This pattern mostly occurs
in large breed dogs with cardiogenic pulmonary edema. The distribution of pulmonary changes is often more helpful than the pattern itself – the pulmonary changes associated with heart failure tend to be located in the perihilar area or in large breed dogs in the caudodorsal lungs.
Radiographic findings of pulmonary parenchymal disease
Pulmonary parenchymal or large airway disease is the main alternative differential diagnosis in the coughing dog. Increased pulmonary opacity in absence of cardiac and pulmonary vascular changes are the main
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43RD WORLD SMALL ANIMAL VETERINARY ASSOCIATION CONGRESS AND 9TH FASAVA CONGRESS








































































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