Correlation of clinical score, intrapleural pressure, cytologic findings of bronchoalveolar fluid, and histopathologic lesions of pulmonary tissue inhorses with summer pasture-associated obstructive pulmonary disease

Objective-To correlate clinical score, intrapleural pressure, cytologic fin dings of bronchoalveolar lavage fluid (BALF), and hislologic lesions of pul monary tissue in horses affected with summer pasture-associated obstructive pulmonary disease (SPAOPD). Animals-8 adult horses affected with SPAOPD and 6 adult horses without evid ence of respiratory tract disease. Procedure-Clinical score, change in intrapleural pressure (Delta Ppl) durin g tidal breathing, results of cytologic examination and bacteriologic cultu re of BALF, and results of histologic examination of pulmonary parenchyma w ere evaluated. Results-Clinical scores for SPAOPD-affected horses (median, 5.75; range, 4. 0 to 7.5) were significantly greater, compared with clinically normal horse s (median, 2.0; range, 2.0 to 3.0). Cytologic examination of BALF from SPAO PD-affected horses revealed predominantly nondegenerate neutrophils. Histol ogic lesions were identified throughout pulmonary tissue and included sever e accumulation of mucus and neutrophils within the small airways, metaplasi a of bronchiolar goblet coils, and mild peribronchial infiltrate, Histologi c examination of specimens collected via percutaneous biopsy was predictive of disease and corresponded to findings at postmortem examination. Clinica l score and Delta Ppl were highly correlated with mucus accumulation in the airways of affected horses. Peribronchial inflammatory infiltrate correlat ed with percentage of neutrophils in BALF of affected horses. Conclusions and Clinical Relevance-Clinical scoring and Delta Ppl provided valid estimates of disease severity. Findings from cytologic examination of BALF of SPAOPD-affected horses varied, although, In most instances, it was diagnostically useful, Severe mucus accumulation in the airways was the mo st remarkable histopathologic finding in SPAOPD-affected horses. Examinatio n of biopsy specimens collected from pulmonary parenchyma was consistently useful in diagnosing SPAOPD.