Ultrasonography in Small Ruminant Reproduction Management

Animal Reproduction Science 130 (2012) 184–186
Contents lists available at SciVerse ScienceDirect
Animal Reproduction Science
journal homepage: www.elsevier.com/locate/anireprosci
Applications of diagnostic ultrasonography in small ruminant
reproductive management夽
P.R. Scott
University of Edinburgh, Easter Bush Veterinary Centre, Roslin, Midlothian, Scotland, United Kingdom
a r t i c l e
i n f o
Article history:
Available online 25 January 2012
Keywords:
Fertility
Pregnancy diagnosis
Reproduction
Small ruminant
Ultrasonography
a b s t r a c t
Modern portable ultrasound machines provide the veterinary clinician with an inexpensive
and non-invasive method to further examine the reproductive tract of both male and female
sheep on farm which should take no more than 5 min with the results available immediately.
Unlike cattle, ultrasound examination of the ovaries is not undertaken because failure to
cycle during the normal season is rare in sheep and there are no common ovarian conditions
causing acyclicity. Accurate diagnosis of foetal number has greatly improved the nutritional
management of late gestation ewes over the past 30 years. Late gestation nutritional supply
in response to foetal demand greatly reduces perinatal lamb mortality by ensuring lamb
birthweight and ewe colostrum accumulation. The contents of vaginal prolapse have been
determined using ultrasonography which has led to an improved method for correction.
A retained foetus when second stage labour is considered to have been completed, and
uterine torsion, can be identified during ultrasound examination allowing timely correction.
Ultrasonographic examination of palpable scrotal abnormalities can provide much useful
information particularly in the diagnosis of epididymitis, orchitis and testicular atrophy.
© 2012 Elsevier B.V. All rights reserved.
1. Introduction
Many veterinarians in cattle practice routinely employ
ultrasonographic examination using 5 MHz linear array
scanners transrectally for examination of the ovaries and
uterus, as well as for the early detection, and possibly
sexing, of bovine embryos. This equipment can also be
employed to provide diagnostic quality ultrasound images
of the gravid ovine or caprine uterus, yielding immediate
results; in these species, examination of the ovaries is rarely
undertaken. A 5 MHz linear array scanner can also be used
for ultrasound examination of the scrotum.
夽 This paper is part of the special issue entitled: Reproductive Health
Management of Sheep and Goats, Guest Edited by G.S. Amiridis and G.C.
Fthenakis.
E-mail address: [email protected]
0378-4320/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.anireprosci.2012.01.013
2. Methodologies for diagnostic ultrasonography in
small ruminant reproduction
2.1. Bladder, uterus, vagina and ventral abdomen
The absence of fleece in the ventral midline and inguinal
area expedites preparation when examining the ventral
and caudal abdomen in sheep. Ultrasonographic examination of the bladder and caudal abdomen are undertaken in
the standing animal, by using either 5.0 MHz linear array or
sector scanners (10 cm versus 20 field depth, respectively).
The caudal abdomen is examined for the bladder and gravid
uterus. The right inguinal region immediately cranial to the
pubis is cleaned with a mild detergent solution diluted in
warm tap water to remove superficial grease and debris.
The right inguinal region is chosen, because the left side
of the abdomen is largely occupied by the rumen. Ultrasound gel is liberally applied to the wet skin to ensure good
contact. The transducer head is firmly held at right angles
against the abdominal wall to image the uterus.
P.R. Scott / Animal Reproduction Science 130 (2012) 184–186
2.2. Obstetrical problems
The contents of the vaginal prolapse can be readily
determined using real-time B-mode ultrasonography with
a 5 MHz transducer and either linear array or sector scanners (Scott and Gessert, 1998a,b).
2.3. Scrotal contents
Sequential examination of the pampiniform plexus,
the head of the epididymis, the testis and the tail of
the epididymis is undertaken, as the linear array scanner is moved distally over the lateral aspect of the
scrotum.
3. Findings in diagnostic ultrasonography in small
ruminant reproduction
3.1. Pregnancy, gestation stage and foetal numbers
Ultrasonography has been successfully employed in
commercial flocks for the past 30 years to determine foetal
numbers and gestation stage, permitting more precise
feeding and management during late gestation (Fowler and
Wilkins, 1984; White et al., 1984; Russel, 1985). Real time
transrectal ultrasonographic scanning of sheep applied
between 24th and 34th day of gestation offers a safe,
accurate and practical means for diagnosing pregnancy
(Garcia et al., 1993). Accuracies of diagnosis of pregnancy
of over 99%, of differentiation of non-pregnant, singleand multiple-bearing ewes of 98% and of determination of
actual foetal numbers of 97% can be achieved in practice at
scanning rates of at least one ewe per minute (White et al.,
1984).
3.2. Obstetrical problems
Ultrasonographic examination is of particular value,
when transabdominal ballotment suggests the presence of
a foetus in utero after delivery of lamb(s) some 12–48 h
previously, but contraction of the cervix prevents further manual examination of the uterus (Scott and Gessert,
2000). This situation may be compounded when the
number of lambs delivered is less than the foetal number determined during a mid-pregnancy examination. It
can prove difficult to differentiate the contracted uterus
from a uterine horn containing a single lamb by transabdominal ballotment alone, but this problem can be easily
resolved by ultrasonographic examination of the caudal
abdomen.
Ultrasonography has been used to monitor uterine
involution post-partum, which was delayed in ewes after
manual correction of dystocia and caesarean section
(Hauser and Bostedt, 2002).
Uterine torsion is a problematic diagnosis in sheep,
because vaginal examination is restricted by the narrow
diametre of the reproductive tract and will not identify
a torsion involving the body of the uterus cranial to the
cervix. Recent work has described the application of transabdominal ultrasound examination of the uterine wall as
185
close to the cervix as possible (ventral midline immediately
cranial to the pelvic brim with the probe head directed
vertically) as a non-invasive means of detecting uterine
torsion in sheep (Wehrend et al., 2002). Oedema of the
uterine wall following torsion resulted in a doubling of
the thickness from 5 mm to over 10 mm. Whilst a 7.5 MHz
scanner was used in this investigation, a 5 MHz linear scanner should provide diagnostic quality sonograms. The early
recognition of this condition and delivery of the lambs by
caesarean section should significantly improve the surgical
outcome (Scott, 1989).
Vaginal prolapse may contain the dorsal vaginal wall,
urinary bladder, uterine horn(s) or both urinary bladder
and uterine horn(s). Urinary bladder is readily identified as
an anechoic (black) area on the sonogram, usually greater
than 10 cm in diametre and compressed dorso-ventrally.
A fold in the bladder wall, which presents as a hyperechoic (white) line, can often be visualized in the ventral
one-third of the anechoic area. Sections through the tips
of uterine horn(s) appear as anechoic circles measuring
3–5 cm in diametre bordered by the hyperechoic uterine
wall; caruncles are not usually observed.
3.3. Scrotal contents
The pampiniform plexus is clearly visible as a collection of thin walled vessels (anechoic cylinders and
circles bordered by hyperechoic walls). The normal testis
appears as a uniform hypoechoic area with a hyperechoic
mediastinum clearly visible. The tail of the epididymis
is distinct from the testis and considerably smaller in
diametre (2–3 cm compared to 6–7 cm) with an obvious
capsule.
The testis is much reduced in size (normal: >7 cm in
diametre, frequently 5 cm for atrophy cases) and appears
more hypoechoic than normal and contains many hyperechoic dots. These hyperechoic dots are thought to represent
the fibrous supporting architecture, now more obvious
due to atrophy of the seminiferous tubules. Ultrasonography was reported to be useful for the diagnosis of
intra-scrotal abnormalities after experimental inoculation
with Arcanobacterium pyogenes into the testicle, especially
during investigation of the long-standing stage of the disease after clinical findings had subsided (Gouletsou et al.,
2004).
Epididymitis caused by Brucella ovis or Actinobacillus
seminis/Histophilus ovis is a major cause of ram infertility
in many countries. Ultrasonographic examination in rams
with epididymitis reveals a normal pampiniform plexus.
Typically, the swollen scrotal contents frequently appear
as multiple 1–5 cm diametre anechoic areas, containing
many bright spots surrounded by broad hyperechoic lines
(fibrous capsule), which extend up to 1 cm in thickness
typical of thick-walled abscesses. The abscesses generally involve the tail of the epididymis, but may extend
to involve the body and head of the epididymis, respectively. The testis is embedded within fibrous tissue reaction
and is much reduced in size and appears more hypoechoic than normal and contains many hyperechoic spots
consistent with testicular atrophy (Karaca et al., 1999).
In unilateral epididymitis, the contralateral testicle is
186
P.R. Scott / Animal Reproduction Science 130 (2012) 184–186
much smaller than normal and appears more hypoechoic.
4. Concluding remarks
Ultrasonography has been used most successfully in
small ruminant reproductive management to determine
foetal number in mid-pregnancy, thereby ensuring adequate energy supply during the final six weeks of gestation.
The speed and very high accuracy of the operators have
ensured the widespread uptake of this technique by
sheep producers in many countries. Such targeted nutrition has major economic and animal welfare benefits.
Combined with ewe energy status evaluation using ␤hydroxybutyrate measurement (Russel, 1985), ultrasound
examination to determine foetal load is the most important
veterinary advice for farmers regarding the management of
pregnant ewes and the benefits of such expertise cannot be
over-emphasised. Moreover, use of ultrasonography during breeding evaluation of rams/buck offers an accurate,
non-invasive technique additionally to the clinical examination of the genitalia. Finally, diagnostic ultrasonography
(Scott and Sargison, 2010) can be employed successfully
for disorders of the genital tract of female (particularly of
obstetrical problems) and male animals.
Conflict of interest statement
The author has nothing to disclose.
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