Chronic Obstructive Airway Disease in a Horse

The endoscopic image in Figure 1 is from within a horse's trachea. In Figure 1, the endoscope is positioned just in front of the main bifurcation of the trachea where it splits into the right and left bronchi (Figure 2) . This is just in front of the horse's heart also known as the carina! The purpose of passing an endoscope down to this level of the horse's respiratory tract is to evaluate for the accumulation of debris (feed material, pus and/or blood) and to perform a diagnostic procedure called a bronchoalveolar lavage (BAL). In this particular case, the horse presented for a chronic cough and exercise intolerance.

Figure 1

Figure 2

As the endoscope was passed down the trachea there was a moderate amount of white foamy fluid along the ventral aspect of the trachea (Figure 2 and 3). This debris is consistent with sputum that originates within the lung tissue and is coughed into the trachea. This finding can be consistent with either pneumonia (bacterial infection) or an allergic airway condition that is also known as COPD/Heaves! To determine the cause of the sputum, a BAL is performed. In this procedure, the endoscope is passed into the primary bronchi until it is lodged within the bronchi. At this point a small volume of sterile saline is passed into the bronchi through the scope and then collected via aspiration. The fluid is analyzed to determine the percentage of different cell types and from this data, it can be determined if the horse has an infection or allergic airway disease.

Figure 2

Figure 3

The importance of determining which disease process is causing the sputum is that treatment for allergic airway disease involves systemic corticosteroid administration which will lower the horse's immune system and significantly worsen any bacterial infection the horse may have!! Hence, it is key to perform the BAL  prior to any treatment to determine if the horse needs antibiotics or steroids or maybe antibiotics plus steroids!! The BAL can be performed stall-side with a sedated horse.