P1130043

13.3.1.3 Abdomen and pelvic region

The abdominal organ easiest to depict by ultrasono-graphy is the stornach (Fig. 1.88). It fills a hypoechoic oval area in the background of the last few ribs and sbows the typical features of an equine stornach, namely the dorsal cul-de-sac and the ventral body.

Nett to the stornach lies the coarseły granular, moderately echoic liver which is passed by the black cords of the large abdontinal blood vessels (Fig. 1.88).

Under optimal conditions it may be possible to de-termine the sex of equine fetuses by means of ultra-sonography (Curran and Ginther 1989). For this pur-pose the location of the genital tubercle between the hind legs raust be deterrnined. The embryonic genital bud differentiates into penis and prepuce in the małe fetus and into clitoris and vulva in the female fetus. Dur-ing feta) development the genital tubercle migrates Erom its origin between the hind legs cranially towards the umbilicus in the małe and caudally towards the tai] in the female. By determining its position ffom about Day 60 of gestation the sex of the fetus can be diag-nosed. In both sexes the genital tubercle consists of a

bilobular, hyperechoic structure. The opli mai time for transrectal ultrasonographic scx determination in equine fetuses appears to lic between Days 60 and 70 of gestation. The sex determination is possible at laler stages too, but then the morę craniovcntral position and the larger size of the fetus may make the optimal depk' don of the caudal body region difficult and not possible in eveiy examinadon.

In contrast to the situadon in bovine fetuses (see Chapter 2.4.2), it has not been possible to determine the sex of equine fetuses by sonographic imaging of the scrotum (Pipers and Adams-Brendemuehi. 1984). One reason for this is that the testes descend much later into the scrotum in the equine fetus than in the bovine fetus. Therefore, the depiction of the scrotum and testes cannot be used to differentiate between the sexes of equine fetuses.

Occasionally, the umbilical cord which floats around within the placental fluids can be seen (Fig. 1.89). A transverse secdon through the umbilical cord shows the typical arrangement of two umbilical arteries and one vein in the equine fetus.