AMBULATORY PRACTICE How to Manage Hydrops Allantois/Hydrops Amnion in a Mare Nathan M. Slovis, DVM, Diplomate ACVIM, CHT*; Kristina G. Lu, VMD, Diplomate ACT; Karen E. Wolfsdorf, DVM, Diplomate ACT; and Walter W. Zent, DVM, Diplomate ACT (hon) Authors’ address: Hagyard Equine Medical Institute, 4250 Ironworks Pike, Lexington, KY 40511; e-mail: [email protected]. *Corresponding and presenting author. © 2013 AAEP. 1. Introduction Hydrops conditions of the placenta in the mare are uncommon, with hydrops allantois being reported more frequently than hydrops amnion.1 The condi- tion in the mare usually develops during the last trimester of pregnancy and is characterized by the excessive accumulation of allantoic (hydrops allan- tois) or amnionic fluid (hydrops amnion). The se- quelae of unnoticed or untreated hydrops allantois/ amnion can be significant, including abdominal wall hernias, prepubic tendon rupture, and cardiovascu- lar shock associated with unattended foaling and dystocia2–4 The condition is often detected by the horse owner as a sudden onset of abdominal enlarge- ment (over a period of a few weeks), ventral edema, varying degrees of colic, lethargy, anorexia, tachy- cardia, and, on occasion, dyspnea associated with intra-abdominal hypertension (Fig. 1). Differential Fig. 1. Mare with hydrops allantois. Note the pendulous “pear- diagnoses include twins, other causes of colic, and shaped” abdomen. causes of ventral edema. Definitive diagnosis requires a trans-rectal exam- ination of the reproductive tract and transabdomi- nal sonogram to detect abnormally abundant fetal whereas a normal volume at term ranges from 8 to fluids. The allantoic fluid volume in mares with 18 L.5 Rectal examination will reveal a large, fluid- hydrops allantois can range from 110 to 230 L, filled uterus of varying tightness with the dorsal NOTES 34 2013 ր Vol. 59 ր AAEP PROCEEDINGS AMBULATORY PRACTICE Fig. 4. Several 5-gallon buckets used to quantitate the volume of allantoic fluid drained during the procedure. Quantitating the Fig. 2. Sonographic image of a hydrops allantois. Note the amount of fluid evacuate is important so that the veterinarian excessive allantoic fluid with a depth of 30.29 cm (normal allan- can calculate the amount of intravenous fluids needed to prevent toic depth : 4.7–22.1 cm). hypotensive shock. wall potentially protruding above the level of the pubis and absence of fetal ballottement.6 Rectal exam for hydrops amnion is similar to hydrops al- appearance. The average normal volume of amni- lantois, except the uterus will not be protruding onic fluid in the mare is 3 to 7 L.9 Excessive amni- above the level of the pubis.6 Transabdominal onic fluid depth will also be noted. Normal fluid sonography for hydrops allantois will reveal exces- depth of the amnionic cavity is 0.8 to 14.9 cm (mean, sive allantoic fluid, with depth Ͼ18 cm highly sug- 7.9 Ϯ 3.5 cm).7,8 gestive of hydrops allantois. The normal amount of Treatment for hydrops usually consists of the allantoic fluid depth is 4.7 to 22.1 cm, with a mean early recognition and drainage of the excess fluid, maximal depth of 13.4 Ϯ 4.4 cm (Fig. 2).7,8 Imaging which usually leads to termination of the pregnancy. of the non-pregnant horn usually reveals an abnor- There has been one report in literature in which mal amount of allantoic fluid. conservative medical management for hydrops am- In hydrops amnion, the sonographic appearance of nion resulted in a viable foal.10 This animal, how- the amnion is turgid, without the normal undulating ever, was noted to be of small stature at 1 year of age and had limb deformities that had to have several procedures performed over the first 10 month of life until they were eventually corrected. The compli- cating sequelae associated with hydropic conditions may include rupture of the prepubic tendon or ab- dominal musculature, inguinal herniation, uterine rupture, abortion, and hypovolemic shock. Uterine inertia associated with the prolonged stretching of the uterus and abdominal musculature is common during parturition.3,10 This inertia can result in dystocia and retention of fetal membranes. Given the severity of the complications associated with hydropic conditions, slow drainage of the excessive fluid(s) with resulting abortion is often recom- mended to salvage the mare.3 The following technique describes how to safely drain excessive fluid and perform a vaginally as- sisted delivery in mares with hydropic conditions. c Fig. 3. Sharp, 32F Trocar to penetrate the chorioallantoic mem- 2. Materials and Methods brane. Note the water proof “waders” worn by the veterinar- ian. This is important to stay dry and comfortable during the The following diagnostic equipment and supplies are draining procedure. needed: AAEP PROCEEDINGS ր Vol. 59 ր 2013 35 AMBULATORY PRACTICE ● Ultrasound machine abdominal musculature or the prepubic tendon. ● 5- to 7-mHz linear transrectal probe These mares should have controlled drainage of the ● 2- to 3.5-mHz transabdominal probe fluid because of the high risk for fatal complications. ● 10- to 14-gauge intravenous catheter In our experience, it is not uncommon to have an ● Two 1-L bottles of 8% hypertonic saline animal that is hypocalcemic. Hypocalcemic pa- ● 40 to 60 L of polyionic crystalloids tients will be more vulnerable to hypotensive shock ● High-flow fluid administration set when the abdominal pressure is released during hy- ● Prostaglandin E (PGE) gela (if cervical dilation dropic drainage. These animals may require intra- is desired) venous calcium supplementation before and during ● or N-butylscopolammonium bromide gelb drainage. (compounded) The placement of a large indwelling intravenous ● Brown gauze catheter (10- to 14-gauge) is important for the ad- ● Lidocaine and scissors for episiotomy (“open” ministration of polyionic crystalloid fluids while the caslicks) allantoic or amnionic space is slowly drained. The ● Sterile gloves and sleeve amount of fluid administered intravenously that is ● 28F to 32F thoracic trocarc (sharp tip) needed to prevent hypotensive shock is dependent ● Sterilized stomach tube on how rapidly the hydropic fluids are drained. ● 5-Gallon bucket Initially, 10 L of fluids will be given during the first ● Euthanasia solutiond 30 to 60 minutes of the procedure. By the end of ● Flunixin megluminee the procedure, it will not be uncommon to have ● Sedation administered an equivalent of one fourth of the vol- ● Detomidinef ume drained intravenously (ie, if 100 L was ● Romifidineg drained, then 25 L had been given intravenously ● Xylazineh over an 8- to 12-hour time interval). If the mare’s ● Prophylactic treatment with antibiotics heart rate becomes greater than 56 to 60 bpm or the ● Head snare animal becomes ataxic or shaking, then the drain- ● Chains and handles age of hydropic fluids should be stopped and a bolus ● Sterile lubricant dose of colloids (Hetastarch,j 10 mL/kg IV) or 8% (2–4 mL/kg IV) hypertonic salinek will be warranted to correct the hypotension and normalize the heart Evaluation of the Mare rate. Once a diagnosis of hydrops allantois or amnion is confirmed, fetal viability is determined, and the ud- Hydrops Drainage der development and milk electrolytes (when war- The technique for drainage involves several consid- ranted) will be assessed to estimate the level of fetal erations, with the most important being safety and maturity. Client communication is critical to es- comfort for both veterinarian and the patient. Lo- tablish the relative value of the mare or fetus, the cation (stocks or stall) is determined by the individ- risks posed to each, and the potential sequelae. ual preference and the condition of the mare. Mares that present early in gestation may undergo The mare may have to be initially sedated and elective termination of pregnancy by intramuscular treated with flunixin meglumine (1 mg/kg IV) for injection of cloprostenoli (500 ␮g IM q 12 h until ease of management. The tail should be wrapped delivery), as long as the amount of fluid is not too and the perineal area should be surgically prepared. excessive to send the mare into shock with sponta- If present, the caslicks should be “opened.” Sterile neous abortion. Cases that occur later in gestation, technique should be followed during the procedure. or those with profound abdominal enlargement with Prostagladin Ea or N-butylscopolammoniumb bro- large volumes of fluid within the uterus, usually mide gel is gently massaged onto the cervix if cervical require controlled drainage of the hydropic fluid be- dilation is desired. A PGE1 gel can be made by crush- fore expulsion of the fetus to control cardiovascular ing 200 ␮g of misoprostoll tablets, resuspending in 1.5 shock. Mares that present during the last 2 to 4 to 2 mL of saline, and further mixing with 1.5 to 2 weeks of pregnancy may be managed by conserva- mL of sterile lubricant. PGE2 gel may also be tive therapy (maintain abdominal wrap for support, used.11 After 5 minutes, the cervix can be gently veterinary evaluation at least weekly, and have vet- dilated manually. The veterinarian should be care- erinary staff available for correction of dystocia and ful not to excessively dilate the cervix because he or hypotensive shock) or partial drainage. The aim of she will not be able to control the rate of drainage of the partial drainage is to maintain pregnancy for as the fluid. If the veterinarian does not want to abort long as possible for additional fetal maturation to the fetus or induce the mare, then the dilation of the occur. A physical exam of the mare will be per- cervix may not be recommended. Once dilated, the formed along with complete blood cell count, fibrin- mucus plug will be easily removed and the chorio- ogen, and serum biochemistry. In the authors’ allantoic membrane can be palpated.