A recto-vaginal fistula in mares can be caused during foaling by the foot-nape posture.
This occurs when the foal is presented with the legs forward without the head. This posture is possible in the mare due to the long limbs and slim head of the foal.
The presence of the foot-nape posture coupled with severe non-productive straining by the mare may cause the formation of a rectovaginal fistula or eventually a third degree perineal laceration. In these cases both the dorsal vaginal wall and rectum are penetrated by the foal's foot directed dorsally by the transverse fold between vagina and vestibule.
Recto-Vaginal fistulae can also be congenital.
Recto-vaginal fistulae are most common in primiparous mares. They are generally caused by a combination of poor alignment of the foal and excessive straining by the mare.
The mare should be kept on her feet and walked around as this can decrease straining efforts. An epidural should be administered to prevent straining. The foal should then be repositioned by forcefully repelling it and if possible lifting the foreleg(s) and placing them under the head. Lubricant and snares may be required to achieve this. If repositioning is unsuccessful but the foal is still alive an incision into the perineum can be made prior to any further attempts to remove the fetus. If the foal is dead this procedure is not necessary and instead partial fetotomy should be performed. This is achieved by sectioning the feet at the radius before removing the remainder of the foal. The damaged tissue should be assessed for bleeding, and any devitalised tissue cut away. As for perineal lacerations, there is usually extensive bruising and laceration of the tissue, therefore repair should be delayed until bruising has subsided and granulation tissue has formed, usually a minimum of 6–8 weeks after foaling or when the foal is weaned.
Prognosis is good as the normal anatomy of both the rectal and vaginal wall is restored following surgical repair. It should be noted that the function of the anal sphincter may not completely return to normal.
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Merck & Co (2009) The Merck Veterinary Manual (Ninth Edition), Merial
McGladdery, A (2001) Dystocia and post-partum complications in the mare In Practice 2001 23: 74-8
Pycock, JF (1997) Self-Assessment Colour Review Equine Reproduction and Stud Medicine Manson
Endell Equine Hospital Foaling Information accessed August 2, 2011
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