The bronchoalveolar lavage is best used in cases where we suspect that the disease that we are looking for is diffuse and when we are not planning to culture the fluid. It is most commonly used for suspected IAD or heaves, but can also be useful for interstitial pneumonia, fungal pneumonia, or silicosis, for example.
Your veterinarian will listen to your horse’s heart with a stethoscope before performing the BAL. Although the BAL is done commonly and is quite safe, we prefer not to do it in a horse with a cardiac arrhythmia or in a horse with a very high respiratory rate. Your veterinarian will also warn you that your horse is likely to cough a lot during the procedure. This can be alarming to owners but it is expected. Before doing the BAL, your veterinarian will sedate your horse very heavily. There are several reasons why heavy sedation is important: first, although people who have a BAL performed on them report that it is not painful, they do report feeling a little panicky – so we want to sedate the horse to keep it from any upleasant sensations; second, we need the tube to go into the horse’s trachea and not the esophagus, so we need to stretch the head out and encourage the horse to leave the airway open; and finally, we want to be able to wedge the tube or endoscope firmly in the lower airway so that we get a true picture of the cells in that area. It will look to you as though your veterinarian is using a lot of sterile fluid to wash the lungs – and it is a lot. We use a half a liter of sterile fluid to do a BAL – the horse’s lungs are enormous and any fluid that is not suctioned back is rapidly absorbed by the great veins in the lung, so there is no risk of drowning your horse, as people sometimes worry about. By using a large, standard amount of fluid, we make sure that we get repeatable results that can be compared to known standards – this is critical to a correct diagnosis. Once your veterinarian has instilled and suctioned back the full 500 mls of fluid, she will place the fluid on ice to keep the cells happy until she is back at the clinic where slides can be made or the fluid can be sent to our laboratory for analysis.