RADIOGRAPHIC AND MICROSCOPIC CORRELATION OF DIFFUSE INTERSTITIAL AND BRONCHOINTERSTITIAL PULMONARY PATTERNS IN THE CAUDODORSAL LUNG OF ADULT THOROUGHBRED HORSES IN RACE TRAINING

Complete thoracic radiographic examinations were performed on 7 horses ranging in age from 24 to 60 months, followed by in-situ lung fixatio n. Radiographs were examined by 3 radiologists for the presence, degre e and distribution of generalised pulmonary patterns within a region o f interest in the caudodorsal lung. Pulmonary tissue was obtained from 12 sites within a designated volume of interest in the caudodorsal lu ng, corresponding to the area of interest evaluated radiographically, and examined for the presence, character and severity of microscopic l esions. Radiographic findings within the volume of interest consisted of mild to moderate bronchial, bronchointerstitial, or interstitial pu lmonary patterns. Interstitial and bronchointerstitial radiographic fi ndings were related to severity of peribronchiolar mononuclear cell in filtrates, the degree of bronchiolar mucosal plication, and alveolar c apillary and peribronchial blood vessel erythrocyte content. The sever ity of the interstitial radiographic pattern was inversely associated with the perceived diagnostic quality of the radiographic examinations . There was no evidence of spatial variation in the severity of the mi croscopic changes examined in this limited pulmonary region. Inter-rat er reliability between radiologists was good in the assessment of diag nostic quality of the radiographic examinations but poor in assessing severity of the primary generalised pulmonary patterns within the radi ographic region of interest.