Ultrasonic Exam of the Mare
Transcript of Ultrasonic Exam of the Mare
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A guide for ultrasonographic
examination of the mare reproductive
system
By
Dr. Derar Refaat IbrahimLecturer of Theriogenology
Dept. Theriogenology
Fac. Vet. Med.
Assiut University
Code- 059-I0
A guide for ultrasonographic
examination of the mare reproductive
system
By
Dr. Derar Refaat IbrahimLecturer of Theriogenology
Dept. Theriogenology
Fac. Vet. Med.
Assiut University
Code- 059-I0
A guide for ultrasonographic
examination of the mare reproductive
system
By
Dr. Derar Refaat IbrahimLecturer of Theriogenology
Dept. Theriogenology
Fac. Vet. Med.
Assiut University
Code- 059-I0
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Ultrasonic exam of
the Mare
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A key feature of the reproductive examination is the ultrasound
exam. With the ultrasound, you are able to see much more than
you can feel.
Ultrasonography is used for diagnosis and management in almost
every aspect of breeding management.
Ovaries
Examination of the ovaries can aid in determining the stage of the
cycle and in predicting or identifying impending ovulation.Characteristics of the ovaries at the various stages of the estrous
cycle are:
o Anestrus: small ovaries, absence of a corpus luteum (CL), no
follicles > 20 mm
OvaryOvary
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o Transition: ovaries of variable size, absence of a CL, follicles
> 25 mm present
o Estrus: ovaries of variable size, absence of an active CL,
may see regressed CL, follicles > 25 mm present, usually 1,
occasionally 2, large (dominant) follicle present
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o Luteal (Diestrus): early - evidence of recent ovulation; later -
ovaries of variable size, follicles may be present and can be
large, CL present
Ovulation
Various parameters have been investigated in an attempt to predict
with accuracy the time of ovulation. By palpation, the estimation of
follicular size and softness are the parameters used.
Increase in follicular size:
Change in follicular shape:
CL
Ovary
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o follicles will frequently develop a "pear-shaped" appearance
shortly before ovulation. The "stem" of the pear is the tract
the follicle develops leading to the ovulation fossa.
Echogenicity of antrum: In many cases, hyperechoic particles will
appear in the antrum close to ovulation. However, if these particles
increase in number and echogenicity, this indicates that the follicle
is likely to be anovulatory.
It is important to be able to recognize ovulation. This is a key event
in the management of endometritis, scheduling pregnancy
examinations, etc. Because mares remain in estrus behaviorally
after ovulation, many mares are bred needlessly after they have
ovulated. Detecting ovulation will reduce unnecessary breedings,
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thereby reducing contamination of the uterus and preserving
stallion reserves for mares that need it.
Corpus luteum
A very recent ovulation may be hard to detect upon examination.
Within 12 - 24 hrs, it will fill in and have a hyperechoic
appearance.
The equine CL has great variation in its ultrasonographic
appearance.
It can have a homogenous echotexture or a trabecular
appearance.
The appearance often changes somewhat as the CL matures. A
CL may remain visible as a smaller hyperechoic structure even
after luteolysis.
Uterus
Examination of the uterus is extremely helpful in determining the
stage of the estrous cycle.
o Anestrus: the uterus is thin and elliptical, with a fairly
homogenous echotexture, bright spots indicating air are not
uncommon
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o Estrus: a characteristic pattern, giving the appearance of an
orange slice or wagon wheel, results due to the edema in the
endometrial folds
o Diestrus: edema is absent, the uterus is round (more so than
during anestrus), homogenous echotexture of the uterus
This is helpful when breeding a mare with shipped semen. For example,
if a mare is given prostaglandin and is presented for examination based
on the time lapse since the prostaglandin injection and the owner's
impression that the mare is coming into estrus, and upon examination
has a 43 mm follicle but no edema in the uterus - should semen be
ordered? Probably not. It may be that that follicle is going to regress and
she will build a new follicle, accompanied by uterine edema, in the next
few days.
Estrus Diestrus Anestrus
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Uterine pathology
The ability to view uterine pathology with ultrasonography is
indispensable in managing the infertile mare. Excessive uterine edema and fluid in the lumen during estrus
before breeding, retention of fluid in the uterus after breeding, fluid
in the uterus during diestrus are all examples of pathologic
problems that would go undiagnosed without the benefit of
ultrasound.
The best way to diagnose this problem is with ultrasonography in
the period after mating.
Fluid present in the uterus at 12 or 24 hours after breeding is a
clear indication for therapy to improve uterine clearance.
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Endometrial cysts, although their role in infertility is somewhat
controversial, may cause problems in early pregnancy diagnosis
and identification of twins. Small cysts do not interfere with normal
pregnancy.
o During ultrasound examinations before breeding, the
location, size and shape of endometrial cysts should be
recorded.
o Photographic records are ideal.
o In this way, archival information is available which will aid in
future examinations and the ability to discern a vesicle.
Large multilobulated cysts
Normal pregnancy
Endometrial cyst
Normal pregnancy
Endometrial cyst
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o Endometritis: fluid present in the uterus has many echogenic
particles inside. The wall is thick and hyper echogenic.
Pregnancy
Early detection of pregnancy is critical for good broodmare
management.
Basically, it not only provides information on whether or not the
mare is pregnant but allows one to manage twin pregnancy in the
most advantageous manner, may serve to give early notice of a
uterine infection and if not pregnant allows mare time to arrange re-
breeding.
Blood vessels
Thick uterine wall
Hyper-echogenic fluid
Blood vessels
Thick uterine wall
Hyper-echogenic fluid
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Ultrasonic Characteristics of early pregnancy in thoroughbred mares. (A) 15 day
pregnancy note the echogenic lines on the dorsal and ventral locations (dorsal and
ventral arrows) on the yolk sac (B) 18 day pregnancy note the Guitar-pick shape of
the conceptus;C21 day pregnancy note the irregular form of the conceptus and
the embryo can be seen as small echogenic dot (white arrow) in the ventro-medial
aspect of the conceptual swelling;D28 day pregnancy note the development of
the allantois (white arrow);E 35 day pregnancy note the dorsal position of the
embryo (white arrow) andF60 day pregnancy, with the fetus recumbent on the
ventral uterine floor.
A B C
D E F
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Normal development of the pregnancy can be monitored and it is
advisable for the practitioner to be familiar with the normal
appearance of the conceptus.
Manipulation of twinning in mare using
Ultrasonography
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*Abortion can be differentiated from normal pregnancy with ease
Normal and abnormal pregnancy 60 days After mating inthoroughbred mares
Normal ultrasonic appearance of the
conceptus in 60 days-pregnant mare
Abnormal ultrasonic appearance
of the conceptus in 60 days-aborted
mare detected ultrasonographically
during routine examination
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Fetal sexing
Fetal sexing is becoming more and more in demand.
Gender determination is based on the location of the genitaltubercle.
o The genital tubercle is the precursor of the penis in the male
or the clitoris in the female.
o The tubercle migrates toward the umbilicus in the male and
toward the anus in the female.
Ideal times for performing the procedure are from 59 to 68 days or
5 to 6 months.
o Before 58 days the tubercle is not distinct enough and has
not migrated sufficiently to make a distinction.
o After 70 days the fetus is hard to reach until it is
approximately 3.5 to 4 months of age.
o As the fetus gets larger, a transabdominal approach may be
preferred.
It is important to mention that accuracy is based on certainty and
that the veterinarian should keep their own written records. If cattle
are available, it is easier to learn the technique on cattle because
the manipulations are easier and they are more tolerant of
prolonged rectal examinations.
Assisted Reproduction Techniques
Ultrasonography has opened up new possibilities for assisted
reproduction in horses.
Oocyte collection for GIFT and IVF is based on ultrasound guided
transvaginal oocyte aspiration.
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Fetal sexing can be performed at approximately 60-70 d and after
approximately 100 d.
Twins, if not managed before fixation of the conceptus or formation
of the endometrial cups, can be reduced to a singleton using
transvaginal ultrasound guided aspiration techniques.