A Retrospective Study of Bronchoalveolar Lavage Cytology in Horses with Clinical Findings of Small Airway Disease

A retrospective of 69 bronchoalveolar lavages (BAL) on horses was done to investigate the relationship between bronchoalveolar cell types and clinical signs in horses with small airway disease. Horses were grouped according to clinical findings. The groups were as follows: I. cough only (n = 14), II. cough with mucopurulent secretions in the trachea (n = 14), III. cough, mucopurulent secretions in the trachea and abnormal lung sounds (n = 24) and IV., all of the above plus dyspnea at rest (n = 17). An asymptomatic group was formed from horses in the same population to serve as control (n = 8). There was a significant difference between cytological profiles of asymptomatic horses and the symptomatic group horses, indicating that BAL findings are different when clinical manifestations of the disease are present. Furthermore, neutrophil counts increased as the severity of clinical signs increased from group I to IV. Some variations of other cell types such as mast cells were also reported. Though a significant increase in neutrophils was predictable in dyspneic horses, there was an absence of typical cytological pictures for the other symptomatic but non-dyspneic groups of horses. This study concludes that BAL is a useful diagnostic tool which allows further characterisation of inflammatory processes when clinical signs if small airway disease are apparent.