AN IMPORTANT SESSION at the
2016 congress of the British Equine
Veterinary Association was devoted to
“The periparturient mare”.
Moderated by James Crowhurst of
the Newmarket Equine Hospital, first
speaker was Barbara Dallap Schaer of
the University of Pennsylvania School
of Veterinary Medicine who described
an approach to abdominal pain in the
post-partum mare.
It was important, she said, to remember
the foal and
to consider
the mare
both from the
immediate
clinical
situation
and from
her future reproductive potential. The
post-partum mare showing abdominal
pain could be presenting with either
severe pain or mild pain due to
uterine contractions or retained foetal
membranes.
Origin of pain
Where does the pain originate? It
may be coming from the uterus
(be particularly vigilant for uterine
haemorrhage), or the intestinal tract
(common problems are large colon
volvulus, devitalised small colon,
rectal tears caused during foaling) or
the urinary tract. Each of these tracts
needs thorough investigation.
This needs to be preceded by
history-taking. The mare’s reproductive
history is important: you need to know
the length of this gestation, how the
foaling went and whether she has had
any previous colic episodes. How has
she responded to medication?
Clinical examination starts
with looking at the animal from
a distance, noting the abdominal
profile, her behaviour and the
degree of discomfort. Then make a
thorough examination, assessing the
inflammatory response (look for scleral
injection and mucous membrane
colour) and doing a complete colic
work-up.
Perform a rectal examination,
paying attention to the reproductive
tract as well as the gastro-intestinal
tract. Use rectal and trans-abdominal
ultrasonography to conform
haemorrhage, peritonitis and organ
displacement. Abdominocentesis
should also be performed: small
increases in parameters may follow
foaling stress but if more than one
parameter is significantly raised (total protein >3.0 g/dl, total nucleated cell
count >15,000 cells per microlitre, or
percentage of neutrophils >80%), this
is clinically significant.
Increased lactate can be an early
warning of haemorrhage, preceding
the fall in packed cell volume or total
solids. Leukopaenia or leucocytosis,
hyperbrinogenaemia or increased
serum amyloid A may indicate an
inflammatory process in either the
gastrointestinal or the reproductive tract.
Timely diagnosis
and
intervention
are essential.
The
examination
needs to be
consistent and thorough, using all available
diagnostics and the clinician’s
knowledge of the conditions that are
likely to be the source of the distress.
The decision to refer needs to relate
to the degree of discomfort and
clinical deterioration: 40% of deaths in
periparturient mares are due to ovarian
or uterine haemorrhage.
Retained membranes
Huw Griffiths of the Liphook
Equine Hospital gave an “Update
on retained foetal membranes”.
The equine placenta is made up
of the chorioallantois, the amnion
and the placental vasculature.
The placental attachment is
diffuse, microcotyledonary and
epitheliochorionic.
When the foetal placental blood
vessels collapse, the chorionic villi
lose their blood supply and shrink.
At the same time the maternal crypts
relax. Thus, the placental attachment
disintegrates and the foetal membranes
are free to respond to the uterine
contractions and so be expelled. This
should happen within three hours of
the foal’s birth.
Retained foetal membranes (RFM) is
rare in ponies and Arabs but common
in draught mares, with a 54% incidence
in Friesian mares. Overall, mares that foal normally have a 2 to 10%
incidence of RFM. The outcome of
RFM can be death following laminitis,
metritis, myocarditis or endotoxaemia
so early, active treatment is essential.
Failure of detachment often happens
in the tips of the uterine horns, with
the non-gravid horn having the higher
incidence. Efficient detachment needs active uterine contractions and
release at the microvilli. An abnormal or diseased placenta can result in
adhesions which will lead to RFM.
The normal uterine contraction
should progress from the apices of
the uterine horns to the cervix so
that the allantochorion inverts on
itself. Caesarean section extends the
second stage of labour and increases
the likelihood of RFM. During the
operation the placenta should be
treated gently, only being removed if
it comes away easily. Too much force
can lead to uterine haemorrhage or
prolapse.
The placenta can be peeled back so
that it is not included in the repair of
the uterine incision. In one study, the
incidence of RFM was 28% following
embryotomy, 30% following caesarean
with a dead foal and 70% following
caesarean with a live foal.
Oxytocin is used to improve uterine
contraction, starting two to three hours
after foaling: 10 to 20 IU can be given
every two hours. This interval is chosen
as although the half-life of oxytocin is
about six minutes, the mare’s receptors
take two hours to replenish.
Oxytocin mobilises calcium but
if testing shows that the mare is
low in serum calcium, 40 IU of
oxytocin can be given in 450ml Ca-Mg
borogluconate. This treatment worked
in 64% of mares. Only 44% of the
mares responded when the oxytocin
was given in saline.
Gentle, careful uterine lavage,
repeated many times if necessary, is
valuable to remove any debris that may
have been left by other methods. RFM appears not to influence future breeding
outcomes.
Uterine tears
Barbara Dallap Schaer came back to
discuss “Diagnosis and treatment of
uterine tears”, explaining that the mare
with a uterine tear may show illness
right after foaling or not for 24 to 48
hours post-partum.
Signs can be insidious: there may be
fever, mild colic or anorexia or there
may be signs of endotoxaemia. These
signs may be caused by other conditions
such as a vaginal tear that stretches into the peritoneal cavity, or damage
to rectum or small colon mesentery, or
vascular compromise to the terminal
small colon or rectum.
Dystocia may cause a tear in the
dorsal body of the uterus while a
normal foaling can be followed by
a tear to the tip of the pregnant
horn. In the mare with suppurative
peritonitis exploratory celiotomy may
be needed to find and repair the tear
and to determine the source of the
trouble which may be coming from the
gastrointestinal tract.
Medical treatment needs to be
aggressive: intravenous antibiotics,
supportive therapy, anti-endotoxaemia
treatment and drain placement and
abdominal lavage. Lavage may be
continuous or repeated daily and
culture of the fluid can guide antibiotic
therapy.
Prognosis is variable, influenced by
the size and location of the tear and the
impact of the subsequent peritonitis.
