Rectal Palpation / Transrectal Ultrasonography
Rectal palpation is a commonly performed procedure in equine veterinary practice as a diagnostic for colic and for many reproductive procedures. Along with transrectal ultrasonography, it is routinely used in reproductive examination of the mare including management of the mare cycle, pregnancy diagnosis and advanced reproduction techniques.
While a very routine procedure, it should be recognised that all rectal palpations carry the risk of trauma, “rectal tear”, to the horse. A rectal tear occurs when the wall of the rectum is weakened or stretched from normal anatomical position. There are different degrees of trauma; however, a full thickness rectal tear is an emergency and life-threatening condition.
Our veterinarians are aware of the potential consequences of rectal palpation. We take suitable precautions to minimise risk to the horse. We may insist on sedation and the use of muscle relaxants or local anaesthetics on young, nervous or resistant horses. A crush is also preferred and generally used to minimise sudden movements during the procedure.
Twin / Multiple Pregnancy
Twin pregnancy is not desirable in the mare. Mares that are allowed to carry twin pregnancies often experience complications as a result. Mares with twin pregnancy are likely to abort twins in the later stages of pregnancy or go into premature labour with an increased likelihood of dystocia (foaling difficulties) and post-foaling complications such as retained foetal membranes. Furthermore, twin foals suffer a higher rate of stillbirth, prematurity or dysmaturity.
Early pregnancy diagnosis, twin recognition by transrectal ultrasonography has greatly reduced the occurrence of twins. We recommend pregnancy diagnosis between 14-16 days of gestation. Recognition of twins or multiple pregnancies at this stage allows separation and reduction via manual ablation with low risk to the mare and remaining embryo. This procedure has a high success rate but occasionally can result in the loss of both embryos.
Twin pregnancy can be difficult to diagnose in the mare depending on stage of gestation. Even in the early stages of pregnancy there can be complicating factors including asynchronous double ovulations, mobility of the embryonic vesicles, and cysts or pathology in the uterus. Later stages of pregnancy may not allow both foetuses to be visualized by ultrasonography due to the anatomy of the pregnant mare. As a result, it is not always possible to guarantee a particular mare is not carrying twins.