Better understanding of airway disease diagnostics in dogs

The latest grant to be given by Healthy Pets New Zealand has been awarded to Rhea Jagdhane of ARC vets. Dr Jagdhane wants to optimise our ability to collect samples from diseased airways in general practice.

Airway diseases are common in dogs, but highly variable.  To correctly diagnose which is present, airway secretions need to be collected, which can be done using bronchoalveolar lavage (BAL), either with or without the use of an endoscope. BAL is effectively a 'wash' or lavage of the lungs with fluid which is instilled and collected via a catheter down the windpipe into the lungs. 

Although endoscopy has some advantages, it is not widely available, is more expensive, and carries a greater anaesthetic risk than performing a BAL without it, which is a far more common technique. Despite this being a commonly used diagnostic method, surprisingly, the optimal method for sample collection has not been established.

The ideal volume of fluid needed for proper lavage is theoretically equal to the volume of the airways being washed. If too little is instilled, fluid will dissipate and not be recovered. Too much results in overflow, dilution of the sample, and unnecessary fluid retention in the lungs.

Current guidelines for calculating the volume to be instilled are based on the patient’s bodyweight. However, we propose that the volume needed is better determined by the diameter of the catheter used. Current guidelines also recommend placing patients on their side while passing the catheter to help guide it into the lowermost lung lobe. The accuracy of this has not been investigated.

Our study aims to investigate whether the diameter of the catheter used determines the volume of lavage solution required to fill the area of lung lavaged, and whether the bodyweight of the patient affects this. Our secondary aim is to determine if placing a patient on their side leads to sampling of the lowermost lung lobe. 

Given BAL is a diagnostic technique used in general practice, we believe supporting a project which aims to optimise the outcome of this diagnostic technique will not only give us better diagnostic outcomes, it is also minimising the potential harm to patients, and giving much greater confidence to clinicians that they are performing the procedure optimally.