The Yolk Sac of the Equine Placenta. Its Remnant and Potential Problems.
Authors: Vilaregut Laura, Lores Marco, Wilsher Sandra
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: The Yolk Sac of the Equine Placenta The equine yolk sac remnant (YSR) represents a unique anatomical feature in horses, with mares being the only species known to develop large and potentially ossified remnants during pregnancy. This comprehensive review synthesises current knowledge about the YSR's structure and clinical significance, drawing on both established literature and novel case presentations to illuminate a poorly understood aspect of equine placental pathology. The authors document a particularly significant case of strangulating YSR leading to fetal compromise and abortion, demonstrating that these structures—often dismissed as incidental findings—can pose serious threats to fetal viability and pregnancy outcome. Understanding YSR development, recognising its radiographic and ultrasonographic appearance, and identifying warning signs of complications such as torsion or strangulation are therefore essential for veterinarians managing high-risk pregnancies, particularly in mares with a history of pregnancy loss. The review establishes a foundation for further research into preventative strategies and early detection protocols that could improve management of this uniquely equine condition.
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Practical Takeaways
- •Awareness of yolk sac remnants is critical for equine practitioners as they are unique to horses and can compromise fetal survival through strangulation.
- •Ultrasound monitoring during pregnancy should include assessment of yolk sac remnant integrity and positioning, particularly if abnormalities are detected.
- •Strangulating yolk sac remnants are a potential cause of unexplained abortion in mares and should be included in the differential diagnosis.
Key Findings
- •The equine species is uniquely known to exhibit large and/or ossified yolk sac remnants in the pregnant mare.
- •Yolk sac remnants can have significant clinical consequences, including cases of strangulation leading to fetal death and abortion.
- •The review synthesizes current knowledge on the equine yolk sac and its remnant as it relates to placental function and fetal viability.