I. Conferencias Magistrales

MEDICINA VETERINARIA Y ZOOTECNIA I. Conferencias magistrales Fetal sexing in early and advanced gestation: more than just a genital tubercle Dr Stefania Bucca, EVMC, PO Box 5825, Doha, Qatar Introduction Fetal gender determination in the mare provides a useful management tool to breeders, by allowing a pre-delivery estimation of the value of offspring. Knowing fetal gender in advance of delivery allows for commercial strategies to be implemented, as the value of stock at sales time is often determined by the gender of the offspring. Diagnostic windows for fetal gender determination First stage diagnosis: early gestation There are two different stages when fetal sex diagnosis can be made by ultrasonography. The first stage is between 57 and 70 days gestation and involves the identification of the genital tubercle by trans-rectal ultrasonography. The genital tubercle is the precursor of the penis in the male and the clitoris in the female and, around day 55 gestation, appears as a hyperechoic equal sign (=), located between the fetal hindlimbs, at an approximately equal distance between the tail and the umbilicus. As gestation progresses, the genital tubercle migrates towards the tail in the female fetus and towards the umbilical cord in the male. The shape of the genital tubercle may change in time into tri-lobed or conical. Disadvantages: Small diagnostic window, a single diagnostic parameter and service required usually at peak time in the breeding season. Second stage diagnosis: advanced gestation The second stage for fetal sex diagnosis avails of a much wider diagnostic window between 100 and 260 days gestation and multiple parameters to validate diagnosis (fetal primary sex organs), but may require a combi- nation of trans-rectal and trans-abdominal ultrasound scanning. Furthermore, fetal gender determination in Memorias del IX Seminario Internacional de Medicina, Cirugía, Ortopedia y Reproducción Equina MEDICINA VETERINARIA Y ZOOTECNIA Mayo - agosto 2018 - Página 194 advanced gestation can be carried out during summer, fall or early winter, at a more convenient time of the year for the busy equine reproduction clinician. Techniques Trans-rectal sonographic viewing of the equine fetus requires standard rectal palpation skills, as per rou- tine ultrasound (US) examination of the mare’s reproductive tract. Thorough skin preparation of the mare’s abdomen is necessary for diagnostic percutaneous US evaluation. Mares are best examined in stocks and although tranquillisation is not usually required, sedation of the mare in advanced gestation reduces fetal activity and lowers the fetus towards the ventral abdomen, enhancing trans-abdominal imaging. Sedation is contraindicated when a trans-rectal approach is adopted. Cranio-caudal and dorso-ventral orientation of the fetus should be initially established. Gender determination is then made by scanning of the caudal fetal abdomen, hindquarters, and buttocks to identify the position of the genital tubercle or the anatomical structure of the primary sex organs. Frontal, cross-sectional and oblique scanning planes may all be required to obtain adequate visualization of diagnostic parameters, particularly during early fetal gender determination. Diagnostic parameters in advanced gestation Fetal gonads are identified within the caudal abdomen as two symmetrical oval structures, ventral to the kidneys, with an oblique orientation of their long axis, converging caudally towards the pelvic inlet. The fetal gonads show a distinctive echotexture that differs from male to female. A marked diversity in echotexture can be appreciated in the female gonad between cortex and medulla with intense peripheral color Doppler signal. Male gonads appear uniformly echodense, with a small outer dotted area (the pampiniform plexus) and a hyperechoic longitudinal, central line (medianistinum). Intense color Doppler signal is detected in these two areas, as they correspond respectively to the pampiniform plexus and the testicular vein. The fetal primary sex organs may be clearly identified on ultrasound as early as 100 days gestation. In the male fetus a fully comprehensive gender diagnosis will include the identification of: penis and prepuce, scrotum/testicular compartments, urethra and gonads. The penis is visualised in the ventro-caudal abdomen, just behind the umbilicus, may be partially/completely encased within the prepuce or appear fully extended and occasionally erect. The urethra can be easily visualised along the ventral shaft of the flaccid or erect penis as a double hyper-echoic line. The fetal scrotum displays a composite echodensity, as the scrotal compartments appear as two symmetrical, oval, less echodense areas. The hypo-echoic appearance of each scrotal compartment relates to the presence of the adjacent gubernaculum testis. In the female fetus the primary sex organs to be visualized to reach diagnosis include: mammary gland, nipples, vulva/clitoris, and gonads. The fetal mammary gland can be visualised in the pubic region and appears triangular or trapezoidal in shape and uniformly echodense. The nipples emerge from the ventral border of the mammary gland as relatively large hyper-echodense areas. No relevant structures can be visualised over the ventral perineum, as opposed to the male fetus, where the urethra runs the entire length, up to the anus. The fetal clitoris is a hyper-echoic structure that bulges out of the buttocks, high up in the perineum. The vulvar commissure can be seen coursing between the anus and the clitoris, in a cross-oblique section of the fetal buttocks. Diagnosis Diagnosis by a single exam per rectum is rapidly attained when the fetus is in posterior presentation, even up to 8 months gestation. The rate of positive diagnosis per rectum reaches 100% between 110 and 130 days gestation, with an estimated time of less than 150 seconds. In transverse presentation gender determination per rectum is easily accomplished when the fetus assumes a ventro-caudal position within the mare’s pelvis. In anterior presentation, the fetal hindquarters can be visualised trans-rectally up to 5 months gestation, according to fetal size and location within the uterus. Rotation of the fetus over the long and short axis is commonly observed up to 8 months pregnancy and frequent changes of presentation occur Memorias del IX Seminario Internacional de Medicina, Cirugía, Ortopedia y Reproducción Equina MEDICINA VETERINARIA Y ZOOTECNIA Mayo - agosto 2018 - Página 195 around 5-6 months. At this time, repeating the exam 5-10 minutes later may find the fetus in a more advan- tageous position for diagnosis. A trans-abdominal approach is usually necessary for gender determination over 5 months of gestation, when the fetus lies in anterior presentation. Finally, proper identification of the mare at the time of examination and the provision of a signed certificate of fetal gender diagnosis should be an integral part of the service offered. Management strategies for the high-risk pregnancy Dr Stefania Bucca, EVMC, PO Box 5825, Doha, Qatar Introduction Most gestational complications in the mare tend to present during the last trimester of pregnancy. These conditions seem to have an initially slow and elusive course and then suddenly precipitate into a life-threa- tening emergency; clear examples include: placentitis (covered elsewhere), uterine torsion, hydrops of fetal membranes and ventral hernias. Uterine torsión The condition usually presents as a mild intermittent colic during mid to late gestation and most mares will continue to pass feces, despite abdominal discomfort. Involvement of the GI tract can generally be ruled out and the mare usually responds well to administration of non-steroidal - antinflammatory / analgesic drugs. When blood supply is severely compromised or a concurrent involvement of the GI tract is present, colic signs are more severe and prolonged. A uterine torsion of ≤1800 may go asymptomatic and resolve spontaneously, but rectal palpation will identify excessive tension over the broad ligament involved. Tor- sions >1800 are unlikely to spontaneously correct and increase the risk of compromised utero-placental blood flow and subsequently fetal oxygenation. Rectal palpation is diagnostic for uterine torsion: one broad ligament is stretched horizontally across the top of the uterus, crossing ventrally and laterally across the midline. The broad ligament on the side of the torsion is usually more caudally placed and runs as a vertical band that disappears under the uterus; ie: in a left uterine torsion, the right broad ligament is stretched horizontally across the uterus. Uterine rupture with subsequent septic peritonitis is the leading cause of maternal fatality. Management of uterine torsion Three different modalities of correction, include rolling the mare under general anesthesia, standing flank laparotomy or ventral midline celiotomy. Hydrops of fetal membranes Hydrops of fetal membranes refers to the overproduction of fluid into either the amniotic or the allantoic compartments (hydramnion or hydrallantois). Both conditions are uncommon, but universally recognized because of their dramatic appearance and consequences. Their etiology remains obscure, although hydramnion has been occasionally associated with fetal cranio-facial deformities, suggesting a potential role of fetal deglutition in the regulation of amniotic fluid volumes. Congenital abnormalities of the fetus, placentitis and twin pregnancies have been associated with hydroallantois and a

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