P1130023

Larger fluid accumulations of a physiological origin wffl not bc found in the nonpregnant uterus. Sono-graphically evident secretions in the lumen of the dies-trous uterus can be seen as a indication of endometritis (Adams et al. 1987, Souires et al. 1988). During estrus smali amounts of ffee fluid may be seen as physiologic, but larger ones as pathologic (Fig. 1.50). Immcdiately after mating, the ejaculate can be seen in the uterine lumen (Ginther and Person 1984 c). Mares whose uter-ine hunina were initially closcd, show fluid accumula-tions containing scattered echoes after service (Fig. 131).

The uterine cervix is depicted relatively poorly. Its ul-trasonic image is morę echoic during diestrus and preg-nancy and is therefore easier to recognize than in estrus.

1.3.2 Pregnant uterus

1.3.2.1 Day 9 to 13 of pregnancy

The young conceptus first becomes visible when it fonris a fluid filled vesicle, Jarge enough to be recog-rtized as a found, anechoic sphere on the ultrasound monitor (Fig. 132). Depending upon the quality of the scanner, this is &st possible, with a variation of only a

fcw days, between Days 9 and 13 of prcgnancy (Day 0 * Day of ovulation or last day of scrvice). When using high resolution ultrasonography with a frequcncy of 5 MHz, 3 to 5 mm large conceptuses can be detected as early ąs on Day 9 of gęstation. On Day 10 the blastocyst measures 4 to 7 mm and will be detectable in as many as about 70% of the mares (Ginther 1986). On the Day 11 it reaches 6 to 9 mm and will be visible in nearly all mares (Fig. 1.53 and 1.55). Around Day 12 the concep-tus has a diameter of 10 to 12 mm and can now be detected even with scanners of lesser resolution using 3 to 3.5 MHz frequencies (Ginther 1983 b).

1.3.2.2 Day 14 to 20 of pregnancy

By Day 14 the embryonic veside has a diameter of 14 to 19 mm (Fig. 1.54 and 1.55). The embryonic vesicle is now large enough to make accurate and reliable posi-tive as well as negative diagnoses under field condition of generał veterinary practice, provided 5 MHz ułtra-sonography is used (Kahn and Leidl 1984). Using ultra-sound of lower frequency, this datę may be postponed by a few days (Chevalier and Palmer 1982). The shape of the embryonic vesicle is spherical and the embiyo proper is not yet visible.