Page 739 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

714 CHAPTER 3

VetBooks.ir Aetiology/pathophysiology 3.175
The exact cause of this condition is currently
unknown, but a number of theories have been pro-
posed. The most accepted explanation is stress failure
of pulmonary capillaries as a result of high transmural
pressure generated during exercise. However, this the-
ory fails to explain the caudodorsal location within the
lung where haemorrhage is first seen or the pattern of
progression that occurs with EIPH. Another hypoth-
esis, one that explains the site of initiation, nature of
the lesion and pattern of progression of EIPH, is that
locomotory forces generated by the forelimb dur-
ing galloping are responsible for damaging the lung.
EIPH is commonly accompanied by airway inflamma-
tion, as detected by BAL, and the role of inflammation
in the pathogenesis of EIPH is uncertain. Increased Fig. 3.175 Severe pulmonary haemorrhage may
upper airway resistance, from nasal, pharyngeal or appear as bilateral epistaxis following intense exercise.
laryngeal dysfunction, can exacerbate EIPH. It is pos- The majority of horses with pulmonary haemorrhage
sible that the cause of EIPH is multifactorial in origin; do not show blood at the nares because the blood is
therefore, multiple variables may need to be taken into carried up the trachea by the mucociliary apparatus and
account to better explain this condition. is swallowed.

Clinical presentation 3.176
The main clinical sign is the presence of blood
within the airways; however, the majority of affected
horses will not actually demonstrate epistaxis as the
blood is often coughed up and swallowed. Horses
may be slow to return to a resting respiratory rate
after exercise, accompanied by prolonged peripheral
vasodilation and sweating. Poor performance may
occur, but in many horses EIPH does not appear to
interfere with performance capacity.

Differential diagnoses
Other causes of epistaxis including guttural pouch
mycosis, ethmoidal haematoma, pneumonia or pleu-
ropneumonia, atrial fibrillation and haemangio-
sarcoma are differential diagnoses. Less common
causes of lung bleeding such as lung abscess, neopla-
sia or foreign body should also be considered. Fig. 3.176 Bronchoscopic view of the carina in a
horse with mild pulmonary haemorrhage as seen
Diagnosis 30 minutes after intense exercise. A small trace of
Epistaxis is only seen in a small percentage of horses blood is visible from the right mainstem bronchus.
with EIPH after exercise (Fig. 3.175). EIPH is cur-
rently diagnosed by endoscopic visualisation of blood exercise to increase the probability of detecting
in the trachea post exercise (Fig. 3.176). Endoscopic haemorrhage from the distal airways in mild cases of
examination is recommended 90 minutes after EIPH (Fig. 3.177).