The prepubic tendon extends from the brim of the pelvis and joins with the abdominal muscles to support the abdomen and abdominal viscera. Mares can rupture (tear) the prepubic tendon, either partially or fully, and the associated muscles of the abdominal wall. Prepubic tendon rupture is an uncommon but serious condition in late pregnancy that might have a poor prognosis and can result in death of the mare and fetus.
The exact cause of prepubic tendon rupture is not known. However, the condition is more common in older mares that have had multiple pregnancies, draft breeds, mares carrying twins, and mares with placental abnormalities such as hydrops (hydroallantois or hydroamnion).
Mares with prepubic tendon ruptures exhibit signs of colic-like pain, elevated heart and respiratory rates, and reluctance to move or lie down. Changes in the shape of the ventral abdomen (underbelly) might be first noted, followed by a rapidly progressive swelling (edema) that can extend from the udder towards the chest. The udder might be swollen, the teats might point toward the mare’s head instead of downwars, and blood might drip from the teats. Touching the ventral abdomen is often resented. Some mares will adopt a ‘sawhorse’ stance with a tilted pelvis and elevation of the tailhead. Other mares might die after a short illness. Diagnosis of prepubic tendon rupture is difficult to confirm and is usually based on characteristic clinical signs.
The choice of therapy for mares with prepubic tendon rupture varies. It will depend on the extent of the rupture, ability to control the mare’s pain, and stage of gestation. The relative value of the mare and foal might also be considered. Complete rupture of the prepubic tendon has a poor prognosis for the mare because the tendon cannot be surgically repaired.
Conservative therapy will usually involve restricting the mare to stall rest, carefully applying ‘belly bandages’ to support the ventral abdomen, and alleviation of pain using a variety of drugs. Progestins might be given to keep the uterus in a quiet (not contracting) state. Close monitoring of the fetus to detect fetal stress is required with frequent ultrasound examinations via the mare’s abdomen to monitor fetal heart rate and activity.
Stage of gestation is an important factor when therapy options are being considered. If the mare is close to term (330 days of gestation or later), induction of labor or a caesarean section might be considered. If the mare is induced, then foaling must be assisted as she has limited or no ability to contract abdominal muscles during active labor. If the foal is successfully delivered, it is considered at high risk of developing problems such as neonatal sepsis. Colostrum supplementation might be needed, and the foal might not be able to suckle the mare due to severe udder swelling.
For mares that rupture the prepubic tendon before 330 days of gestation and in which pain can be managed, a decision might be made to support the mare so the fetus can reach 330 days of gestation or longer. The last part of pregnancy is very important in determining viability of the foal, as most of the fetal maturation that ensures the foal is ready for life outside the uterus happens in the last 10 days of gestation. For mares in which pain cannot be well managed, euthanasia should be considered.
Mares with prepubic tendon rupture that survive foaling or caesarean section should not be bred again. Some mares that survive foaling might subsequently need to be euthanized due to intractable pain.
This article was first published in the Equine Disease Quarterly (EDQ), which is produced by staff at the Gluck Equine Research Center of the University of Kentucky, and funded by Underwriters at Lloyd's, London.
This article was written by Erica Gee, BVSc, PhD, DACT, of the School of Veterinary Science, Massey University, New Zealand.