Considerable variation has been reported in total cell counts and concentration of biochemical markers due to variable recovery of pulmonary epithelial lining fluid (PELF) in bronchoalveolar lavage (BAL) fluid. A number of chronic respiratory conditions can be difficult to diagnose definitively and accounting for dilution of PELF may allow us to better differentiate respiratory disease. Differentiation of various chronic respiratory diseases may be made via analysis of BAL fluid using urea concentration of BAL relative to blood urea concentration as a marker of dilution of PELF. Assessment of cell counts after adjusting for dilution may allow differentiation of the primary disease process in dogs presenting with respiratory signs.

Client-owned dogs presenting for investigation of respiratory disease were included. All dogs had a BAL performed and BAL cell counts were corrected after using urea as a marker for dilution and comparison of urea in blood to that of urea in BAL fluid. A final diagnosis of respiratory disease was made after retrospective analysis of all diagnostic investigations and response to treatment.

Seventy-two BAL samples from a total of 48 dogs were analysed and thirteen primary causes of respiratory disease identified based on diagnostic investigation including BAL cell cytology and treatment response. Respiratory diseases were also assigned to inflammatory, non-infectious, infectious, upper respiratory tract or respiratory neoplasia categories based on the disease diagnosed. There was no statistical difference in the adjusted total cell counts of BAL fluid (BALF) from dogs with different respiratory diseases or disease groups. Mycoplasma spp had no effect on the total cell count in dogs with chronic bronchitis.

This study suggests total cell counts of BAL fluid corrected for dilution by urea concentration cannot be used to distinguish between different respiratory diseases. A larger number of cases and cross section of respiratory disease may further identify significant differences in total and differential cell counts of various different diseases.

Disclosures

This study was funded by the Australian Companion Animal Health Foundation and supported by the Australian and New Zealand College of Veterinary Scientists Research Grant Amanda Paul and Jason Stayt also indicate that they have no affiliations or financial involvement with any organization or entity with a financial interest in, or in financial competition with, the subject matter or materials discussed in this article. Caroline Mansfield has funding for research provided by Australian Research Council, Canine Research Foundation (Australian Kennel Club), Comparative Gastroenterology Society, Nexvet Biologics, PlasVac, Blackmores, Hills Pet Nutrition. She is also provided an Honoraria for travel/speaking in 2017 provided by Nestle Purina, FSAVA. Peter Irwin has funding from the Australian Research Council, Canine Research Fund and Australian Companion Health Foundation for ongoing research projects.