Biomedical Engineering Reference
In-Depth Information
from early signs of threatened or impending abortion where
intrauterine hemorrhage may be associated with hematoma
formation. Both can result in extensive vaginal hemor-
rhage. Early resorptions can also be identified by an inap-
propriate GS size for the expected GD, poor development
of the chorionic villi/placenta, or a diminishing GS when
examined consecutively. A small volume of intrauterine
fluid within an enlarged uterus is also suggestive of early
abortion/resorption, although small volumes of intrauterine
fluid may be observed in some nongravid animals during
the follicular phase of the menstrual cycle.
The incidence of live-born twins in Old World monkeys
is extremely rare (
Tarantal and Hendrickx, 1988d
).
Compilation of the published data for the rhesus indicates
a twinning rate of 0.2% (10/4991). However, the appear-
ance of twin GS
e
one with a viable embryo and one
anembryonic
e
has been noted sonographically, which
suggests that the incidence of multiple gestations is prob-
ably greater than reported. These data are similar to the
“vanishing twin” phenomena as noted in the human,
although the outcome in the macaque appears
duration. Other types of cystic structures can be imaged in
the mesentery (common; 1
e
10 mm in length; benign),
ovary (may be follicles or theca lutein cysts), uterus (hydro-,
pyo-, or hematometra), or cervix (nabothian cysts) and can
be aspirated, if deemed appropriate. Other pelvic and/or
uterine solid neoplasms can be detected and biopsied to
confirm the diagnosis.
The use of ultrasound-guided interventional procedures
in these species has been described and its application in
both the pregnant (
Tarantal, 1990
) and nonpregnant female
(
Tarantal et al., 1990
) established. The primary advantage
of these techniques is that they obviate extensive surgical
procedures with all the associated risks, costs, and potential
trauma.
Among the New World monkeys species, ultrasound
has also been used to diagnose pregnancy and monitor fetal
growth in squirrel monkeys (
Narita et al., 1988
). Pregnancy
can be identified on GD 25 with detection of the GS;
cardiac activity can be confirmed approximately 2 weeks
later. Pregnancy in marmosets can be diagnosed by ultra-
sound at around GD 30 by the presence of a hypoechoic
area between the hyperechoic uterine walls. Gestational
sacs are clearly evident by around day 30, and heart beats
are reliably detected by around day 50.
less
favorable.
For those nonhuman primate females determined to be
nonpregnant, recording baseline data of uterine size and
appearance has been suggested (
Tarantal and Hendrickx,
1988d
). These data include measurements of total uterine
length (uterine body and cervix, normal
Prenatal Growth and Development
Hendrickx and Dukelow (1995)
reported routine observa-
tions for evaluating prenatal growth sonographically for
M. mulatta and M. fascicularis at the California Primate
Research Center. These routine observations included
mean GS dimension (GD 14
e
50), GL (~GD 23
e
60), head
measurements (biparietal and occipitofrontal diameters,
head area, and circumference), abdominal area and
circumference, and humerus and femur lengths (see
Tarantal and Hendrickx, 1988b,c
for methods). These
measurements are compared with normative growth data or
predicted values (
Tables 8.8
e
8.10
) for each species and are
used in combination to obtain greater accuracy in either
predicting or confirming gestational age (
Tarantal and
Hendrickx, 1988b
). In addition, embryonic/fetal heart rates
can be obtained during the examination period and
compared with the expected normal rates.
Documentation of normal and abnormal growth and
development of the conceptus is particularly pertinent, both
from a colony maintenance standpoint and for research-
oriented purposes. The standard sonographic evaluation
performed during the second trimester (~GD 75
e
90) is
incorporated in order to assess anatomical configuration,
determine gender, monitor condition, and evaluate
placental development. This is the optimal time for making
judgments about conformation of the fetus since the
volume of amniotic fluid (i.e. the ratio of fetus to the fluid
volume) provides an excellent sonographic “window.”
range for
M. mulatta (Mm) is 52.0
7.1 mm; M. fascicularis (Mf) is
43.6
9.2 mm); uterine body length (Mm 28.2
5.0 mm;
Mf 23.7
4.3 mm), width (Mm 17.8
3.4 mm; Mf 16.8
2.8 mm), and height (Mm 17.5
2.7 mm); uterine shape, contour, and homogeneity;
appearance of the ECE; and endometrial thickness. This
information is particularly useful for documenting early
absorptions/resorptions and for evaluating nonreproductive
females. Alterations in uterine size, contour, and/or
appearance (i.e. changes in echogenicity) may suggest
a pathological process such as leiomyoma, carcinoma,
adenomyosis, endometritis, or endometrial hyperplasia.
Foreign bodies and seminal plugs/coagulum can be readily
identified within the vaginal canal, fornices, or cervix/
endocervical canal by an increase in echogenicity (hyper-
echoic) and in some cases by acoustic shadowing.
Of particular importance is the detection of endometri-
osis, a relatively frequent finding in laboratory-housed
macaques with a history of repeat hysterotomies. Endo-
metriomas may occur in single or multiple sites attached to
the uterus and/or adnexal structures, either homogeneous or
septated, and will usually appear cystic with well-defined
borders and some internal echoes. Diagnosis can be
confirmed by ultrasound-guided aspiration of “chocolate
fluid,” which is a characteristic feature. In some cases,
endometriomas may be complex in appearance (cystic and
solid components) or predominantly solid if of longstanding
3.4 mm; Mf 16.3
