Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. I. Clinical profile of horses

Detailed physical and clinical examinations were performed on 26 Thoroughbred racehorses which were used subsequently in a series of studies to investigate the contribution of the pulmonary and bronchial arterial circulations to the pathophysiology of exercise-induced pulmonary haemorrhage (EIPH). Twenty-five of the horses had been retired from race training in Hong Kong during the 1984-85 season, all but four raced that season; one horse had been retired the previous season. The average number of races for the group that season was 4.1 +/- 2 with an average distance of 1502 +/- 216 metres, mean racing speed 15.5 +/- 0.5 metres/sec. Time from last race to necropsy was 177 +/- 155 days, range 12 to 572 days. All but one horse had a known history of either EIPH or epistaxis. Time from last recorded incident of expistaxis (17 horses) to necropsy was 156 +/- 141 days, range 12 to 513 days, with a longer interval since last recorded endoscopic observation of EIPH. Focal abnormal lung sounds were detected in the dorsocaudal lungfields on auscultation during rebreathing in three horses and six had tracheobronchial cytology consistent with previous episodes of pulmonary haemorrhage (haemosiderophages). No other characteristics which might have allowed separation of this group of horses from other Thoroughbred horses recently in race training were identified.     

Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. VI. Radiological/pathological correlations

This study was initiated to determine if the extent and intensity of lung lesions associated with exercise-induced pulmonary haemorrhage (EIPH) in horses could be predicted from thoracic radiographs. Sets of thoracic radiographs from 24 horses with varied histories of EIPH were subjectively coded for radiographic quality, and perceived extent and intensity of diffuse interstitial opacity by three radiologists who had no knowledge of the corresponding autopsy results. Codes assigned from radiographs for the chosen parameters were compared with coded estimates of lung surface staining assigned at post mortem and volume measurements of haemosiderin deposits and bronchial arterial neovascularisation recorded from lung slices in separate studies. The non-parametric Spearman rank correlation test was used to test for statistical significance. All radiographically coded estimates of lesion severity were positively correlated with post mortem measurements of actual lesion involvement, but only the correlation between coded estimates of lesion opacity versus haemosiderin deposits and bronchial artery neovascularisation were statistically significant (P less than 0.05). Correlations between radiographic codes for lesion extent versus haemosiderin deposits and neovascularisation were just beyond the level of significance (P greater than 0.05 less than 0.1). These findings indicate that there are graded, radiographically discernible increases in interstitial opacity related to actual lesion severity. However, under the conditions of the study, accurate prediction of lung pathology in individual cases based on radiographic criteria was precluded by the wide variance of the coded values. The authors believe that with good radiographic technique and careful criteria selection, satisfactory prediction of lesion severity in EIPH cases could be achieved.     

Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. VIII. Conclusions and implications

This paper reviews a series of clinical, post mortem and imaging studies on exercise-induced pulmonary haemorrhage (EIPH) performed on 26 Thoroughbred racehorses. Post mortem techniques included routine gross, subgross and histological examination; coloured latex perfusions of pulmonary and bronchial circulations; and microradiography and computerised tomography scans of lungs with contrast injected vasculature. The major lesions were multiple, separate and coalescing foci of moderately proliferative small airway disease accompanied by intense neovascularisation of the bronchial circulation. As a result of bronchial artery angiogenesis, the systemic circulation dominated the vascular supply of the air exchange structures in affected areas, producing an apparent left to right shunt. Extensive areas of sequestered haemosiderophages indicated previous haemorrhage from vessels apparently supplied by the bronchial arteries. Diffuse and focal parenchymal destruction and connective tissue reactions in affected areas were considered to be secondary to localised haemorrhage and macrophage-induced damage. The aetiology of EIPH was not determined, but the multifocal, small airway-centred lesions indicated that low grade bronchiolitis, possibly of viral origin, was a factor. Gravitational effects also appear to contribute to dorsal distribution of the lesions. The mild focal and subclinical lesions confined to secondary lobules are thought to evolve into the serious lung pathology observed in EIPH cases through the effects of localised hypoxia induced by maximal exercise and partial airway obstruction. Once initiated, a vicious cycle of increasing inflammatory damage and further local bleeding is set in motion.     

Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. III. Subgross findings in lungs subjected to latex perfusions of the bronchial and pulmonary arteries

Latex was injected under pressure into bronchial and pulmonary arteries of the inflated lungs of Thoroughbreds and transverse sections taken to calculate the area of lesions resulting from exercise-induced pulmonary haemorrhage. Extensive areas of dense brown haemosiderin varying from 0 to 45 per cent of total lung volume were identified, predominantly in the dorsocaudal lungfields. Bronchial arterial proliferation appeared to have replaced the pulmonary supply in affected areas of the lung. Closely associated with the staining and bronchial arterialisation, there was widespread small airway disease. The most severely affected bronchioles contained thick gelatinous or mucous exudate or mucoid plugs and had grossly thickened walls. These lesions suggest that the source of haemorrhage in exercise-induced pulmonary haemorrhage is from alveolar capillaries anomalously supplied by the bronchial arterial circulation through the development of pathological shunts. Small airway disease is suggested as being of major importance in the pathogenesis of the disease and may have led to the initial proliferation of the bronchial circulation.     

DETECTION OF A LIVER TUMOR IN A BEAGLE DOG USING SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY

This case report describes the detection of a liver tumor in an 11–year-old female Beagle dog using single photon-emission computed tomography (SPECT). A mass was palpated in the cranial abdomen during removal of recurrent mammary tumors. A conventional nuclear medicine liver scan, following injection of ^99mTc-sulfur colloid, was equivocal. SPECT was then performed in a second procedure, using a simple system that rotated the dog before a gamma camera. Transverse plane images clearly showed a spheric space-occupying lesion, found at gross necropsy and confirmed histologically as a hepatoma. Discrete liver tumors may be detected more readily and their size determined more accurately using SPECT than with conventional nuclear medicine approaches.     

Dietary molybdenum as a putative copper antagonist in the horse

Four horses were stabled and fed a diet of hay ad libitum, and 2 kg oats per animal per day, for a month. The basic diet was then supplemented with molybdenum, at a rate of 20 mg/kg dry matter for 4.5 months. For one month of this period the diet was supplemented also with sulphur at a rate of 1.2 g/kg dry matter. Analyses of jugular blood samples, obtained at intervals varying between two and 20 days, showed no evidence of a decline in total plasma copper or of an increased proportion of trichloroacetic acid (TCA) insoluble copper in plasma over this period. In separate studies, two other horses were given 99molybdenum (molybdate, 20 to 28 mg Mo, 4 mCi per animal) per os, initially while being fed the basic diet and later while maintained on the molybdenum supplemented diet. 99Molybdenum appeared rapidly in plasma, but the radioactivity was then quickly cleared (half-life 7 to 10 h). The 99molybdenum present was identified as (99Mo)-molybdate. There was no evidence of the persistent, protein-bound (99Mo)thiomolybdates which appear in ruminants. These studies indicate that increased dietary molybdenum is unlikely to interfere with copper metabolism in horses.     

Empyema of the equine paranasal sinuses.

A survey of 28 cases of chronic purulent infection of the sinuses in the horse showed a relationship between incidence and age, and a probable relationship with breed. Dental disease was apparently the cause of half the cases. The conventional treatment of trephination followed by irrigation with antiseptic solutions resulted in freedom from recurrence of the disease for over 1 year in 17 of the 28 horses. Antibiotic therapy appears to be useless in chronic empyema. The prognosis is adversely affected by the development of facial swelling, a sign seen usually only in long-standing cases.