Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. II. Gross lung pathology.

This research investigates the physical effects of exercise-induced pulmonary haemorrhage (EIPH) in Thoroughbred horses, based on detailed post-mortem examinations of the horses’ lungs. Notable findings include abnormal lung discoloration and changes to the bronchial arteries in affected areas, which are associated with factors like small airway obstruction and decreased tissue compliance.

Overview of the Study

• The study was centered on understanding the implications of Exercise-Induced Pulmonary Haemorrhage (EIPH) in Thoroughbred horses. EIPH is a condition where strenuous exercise results in bleeding from the lungs. This condition is prevalent in racehorses but its exact cause and biological implications are not fully known.
• As part of the research, detailed post-mortem examinations of the lungs of 26 Thorougbred horses of known EIPH status were carried out. This deep, investigative approach ensured a comprehensive analysis of the anatomical and physiological changes brought about by EIPH.

Key Findings

• The most consistent and significant finding was the detection of bilaterally symmetrical, dark discolouration in the dorsocaudal regions of the caudal lung lobes. In other words, certain backward and downward parts of the lower sections of the lungs were noticeably darker in color.
• In more severely affected lungs, these discoloured patches extended towards the top (cranial) part of the dorsal (back) surfaces of the lungs, with some cases involving approximately one third of the total lung surface.
• These discoloured areas were denser than normal, indicating potential damage, as healthy lung tissue is typically light and airy.
• Additionally, these areas collapsed less readily than healthy lung tissue, often contained trapped air, and were slow to inflate, implying the possibility of partial small airway obstruction or a decrease in the lungs’ natural elasticity (compliance).
• The bronchial arteries, which supply blood to the lung tissue, were found to be more prominent in the discoloured regions. This could be a vital clue in understanding the vascular changes associated with EIPH.

Conclusions Drawn

• The discoloured lesions were directly related to previous instances of EIPH, and were believed to have a complex pathogenesis, meaning that their development involved a wide range of biological processes and changes.
• Signs of partial small airway obstruction and decreased tissue compliance were also associated with these lesions, reinforcing the insight that EIPH can significantly affect lung functionality.
• The involvement of the bronchial arterial circulation was also notable, hinting at a potential underlying vascular component connected with physiological changes in the lungs due to EIPH.