Exercise induced pulmonary hemorrhage (EIPH) leads to significant economic losses in the horse racing industry. In addition to racehorses, EIPH can also affect jumpers, polo horses, barrel racers, pullers, and ropers. Endoscopic examinations reveal that 40-90% of horses experience EIPH after sprint exercises; however, the limitations of the endoscope may prevent accurate diagnosis in many horses, suggesting that the actual incidence could be as high as 100%. Research conducted in 2009 has begun to focus on the underlying mechanisms of this common disorder in racehorses. This report provides information on our understanding of EIPH and the effects of furosemide (Lasix) on both EIPH and performance. Additionally, links to related articles and summaries of recent scientific findings are provided.

Examining the lung tissues of affected horses reveals several abnormalities localized in the dorso-caudal regions of the lungs. These findings help us understand what happens to these horses during exercise over time:- Increased thickness of the vein walls - Accumulation of broken-down red blood cells (hemosiderin) - Capillary neovascularization - Scarring and fibrosis due to collagen depositionThese results support the hypothesis that repeated strenuous exercise leads to increases in pulmonary venous blood pressure. This pressure causes the vein walls to undergo remodeling, resulting in the accumulation of collagen, venous occlusion, and capillary hypertension. When subjected to these high pressures, the capillaries experience stress failure, resulting in bleeding and the accumulation of hemosiderin, which is followed by lung fibrosis.