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13.4.2 Abnormal pregnancy

There can be many signs of abnormal cvents during advanced pregnancy. The shape and size of the feta! sac can no longer be assesscd, bccausc it has become too łaige. Ultrasound esaminations at this stage concen-trate on the fetus (see also Chapter 133). In cases of imminent abortion it has been noted that the fetus had a heart ratę beyond the outer limits observed in intact pregnanries.

Often the fetus is not immediately expclled after it has died. A steady decline in the amount of placental fluid can be observed by ultrasonography in such cases. The sonoanatomy of the fetus also changes. Many struć-tures that can be seen in live fetuses become less elear (Fig. 1.98). Parenchymatous organs in particular, which undergo rapid postmortem changes and are normally traversed by a rich supply of blood vessels change their typical appearance (Staudach 1986). The hypoechoic appcarance of blood vessels changes to look like the surrounding tissues. because of intravascular coagula-tion of blood. Soft tissues may loose their typical struc-ture and look much less differentiated. Ossified bonę segments retain their echogenicity and will therefore re-main yisible for a much longer period of time. Even once the placental fluids have totally disappeared fetal echoes can usually be found for several morę weeks (Glnther et al. 1985).

In hydrallantois and hydramnion cases the most ob-vious finding is the extensive amount of fluid in the uter-us. There is an excessive accumulation of placental fluids between the uterine wali and the fetus. In some instances this is so extcnsivc that it exceeds the scanning depth of 20 to 30 cm of Iow frequency ultrasound (Fig. 1. 99) and the fetus can not be reached traasrectally. During transcutaneous examination it might be detecta-blc in the vicinity of the matemal navel.

1.3.43 Post partum uterus

During the first few days of the post partum period the uterus of most mores cbntains some lochial secrc-tions. The depth of the fluid accumulation can reach several ccntimetcrs, evcn in normal post partum mares (Fig. 1.100). It sometimes happens that on the basis of an ultrasound examination a uterus is found to be free of fluid during the first few days after parturition (Fig. 1.101); not infreąuently, however, lochial fluid may be found in the same uterus during a foliow-up examina* tion l to 2 days later (McKinnon et al. 1988). The pro-portion of mares that do not have any fluid łeft in their uterine lumina incrcases significantly after Day 7 post-partum. At the time of foal heat only 25 % of mares have lochial secretions in their uterus. In the case of an abnormal postpartum period with the retęntion of lochia the resultant fluid accumulation in the uterus can be strikingly cxtensive and many centimcters deep (Fig.

Fig. 1.102: Lochiometni in a marę 4.5 days postpartum. The fluid pool in the uterus (arrows) extcnds many centimcters dcep. The same day 1.51 of fluid were drained from this uterus.