How to Use Umbilical Vessel Water Infusion to Treat Retained Fetal Membranes in Mares

Using simple tools that are readily available to the equine practitioner (stallion catheter, hose adapter, and garden hose), retained fetal membranes can be easily and safely removed.

1. Introduction

Expulsion of the fetal membranes after delivery of a foal is generally an uncomplicated event. Normal fetal membrane expulsion occurs 1 to 2 hours after delivery of the foal. Fetal membranes are considered retained in the mare if they are not expelled by 3 hours after delivery.^1,2  The incidence of retained fetal membranes is not high, with reports of membranes being retained in about 2–10.6% of postpartum mares.¹  Disturbances in foaling (dystocia, prolonged gestation, placentitis, Caesarean section, or hydropic conditions) have been known to result in retained fetal membranes although no direct relationship exists between foaling abnormalities and incidence of retained fetal membranes. Breed predilection for retained fetal membranes has been identified. Friesian mares are reported to have a high incidence (>50%) of retained fetal membranes.³  A similar rate of membrane retention (42% over 4 years) was recently reported in Standardbred mares from New Zealand.⁴

The pathophysiology of membrane retention in mares has not been elucidated; therefore, preventative and/or treatment strategies are largely empirical. It has been postulated that myometrial exhaustion^1,5  after dystocia or prolonged delivery and/or inadequate oxytocin release contribute to retained fetal membranes in mares. Varying portions of the membranes may be retained with the non-gravid horn or the allantochorion being the most common portion of the membranes to be retained. Complications of retained fetal membranes can range from none to toxic metritis, septicemia, and laminitis.^1,5  Given the life-threatening nature of these conditions, retained fetal membranes are considered an emergent condition requiring immediate treatment.

Treatment for retained fetal membranes centers on prompt removal of the membranes. The traditional methods used to recover retained fetal membranes include administration of oxytocin^1,6 (repeated oxytocin injections [10–20 IU IM every 1–2 hours] or the administration of 1.0 to 1.5 IU oxytocin/minute [60–100 IU oxytocin in 1 liter saline IV over 1 hour], administration of calcium borogluconate,⁷ repeated uterine lavage, the Burn’s technique [for intact membranes],⁸ and manual removal of membranes). Umbilical artery infusion of bacterial collagenase has also been used to treat retained fetal membranes in mares.⁹ The method selected for removal of retained fetal membranes is dependent on effectiveness, safety, cost, and convenience. Mares housed in hospital conditions or on well-managed farms can be administered drugs frequently such as multiple doses of oxytocin. Further, mares housed under intensive management conditions can be monitored closely for secondary conditions to retained fetal membranes such as toxemia, laminitis, and uterine prolapse. Mares housed in general field conditions without ready access to veterinary care may require more rapid, but safe, management of retained fetal membranes.

This paper describes a novel and practical approach to removing retained fetal membranes using a low-pressure infusion of water into the umbilical vasculature. This procedure causes stretching of the umbilical vessels, interstitial swelling of the membranes, and subsequent detachment of the microvilli, resulting in rapid and gentle separation of the fetal membranes from the endometrium.

2. Materials and Methods

Between 2007 and 2015, 147 broodmares with retained fetal membranes longer than 3 hours were treated by low-pressure infusion water into either the umbilical artery or vein. The mares were all located in the Netherlands and consisted of 47 Friesian mares (32%), six Draft horse mares (4%), 12 ponies (8%), 69 Warmblood mares (47%), and a mix of Arabians, Andalusian horses, Haflingers, or Iceland ponies (9%). All mares had normal parturition, dystocia, abortion, or stillbirth. Mares undergoing Cesarean section were not included in this report.

Initial treatment of mares consisted of a maximum of three oxytocin^a (10–20 IU, IM) injections every 1–2 hours. Mares that did not expel fetal membranes after oxytocin administration underwent infusion of the umbilical vasculature. Mares were restrained in stocks or in a box stall. The perineal area of the mare was cleaned prior to the procedure. Immediately before starting the procedure, mares were administered oxytocin^a (10 –20 IU IM). A foal nasogastric tube or stallion catheter (with a maximum external diameter of 9 mm) was attached to a water hose using a hose connector with flow control valve (Figs. 1 and 2). An umbilical vessel (vein or artery, both are equally effective) was incised longitudinally using a standard scalpel blade (Fig. 3). The catheter, attached to the flow control fitting on the garden hose, was slowly advanced up the vessel under low water pressure until it could not be advanced further (Figs. 4 and 5). The veterinarian manually held the tube in situ and adjusted the water flow depending on the physical reactions of the mare (Fig. 6). In mares showing mild discomfort (shifting weight, mild efforts to kick), fluid flow was discontinued for a short period to allow the mare to relax and progress of placental release to be assessed. If the membranes remained firmly attached, low-pressure fluid infusion was resumed. After 3–5 minutes of intravascular fluid infusion, gentle traction was placed on the neck of the membranes at the mare’s vulva. Traction was continued until the membranes were released (Fig. 7), the mare demonstrated discomfort, or tearing of the membranes was suspected.
 

3. Results

In the majority of the cases (135/147; 91.8%), full separation and expulsion of the placenta occurred within 5–10 minutes of umbilical vasculature infusion. In four mares (2.7%), incomplete separation and tearing of the membranes occurred. [...]