Aortic-iliac thrombosis in horses

Area of Science:

• Veterinary Pathology
• Equine Medicine
• Vascular Biology

Background:

• Vascular obstruction of the hindlimbs is a recognized clinical condition in horses.
• Lesions are found in the aortic quadrifurcation and distal arteries.

Purpose of the Study:

• To characterize the pathological findings of hindlimb vascular obstruction in horses.
• To investigate the potential pathogenesis and contributing factors of these vascular lesions.

Main Methods:

• Clinical diagnosis in 15 horses.
• Necropsy characterization in 10 horses (8 clinically diagnosed, 2 incidental findings).
• Histopathological examination of arterial lesions.

Main Results:

• Clinical signs included progressive exercise intolerance and hind-leg lameness.
• Post-mortem findings revealed occlusive fibrous masses and thrombi in the aorta and iliac/femoral arteries.
• Lesions involved organized fibrous tissue, with intact internal elastic lamina and largely unaffected tunica media, except in distended arteries.

Conclusions:

• The pathogenesis remains unresolved, with theories including strongyle-related thromboemboli or spontaneous fibrous intimal plaque organization.
• Hypercoagulability may contribute in specific cases (e.g., nephrotic syndrome).
• Routine examination of the aortic quadrifurcation is recommended for early detection and understanding lesion progression.