Uterine artery rupture
Rupture of reproductive tract blood vessels is most commonly seen at or soon after
foaling. Uterine artery rupture is more common in older (>12 years old) multiparous
brood mares, as a result of sclerotic degeneration of the vessels; however, fatal
haemorrhage can also result from ruptured ovarian, vaginal or pudendal vessels, or
from tearing of the cervix, uterine or vaginal walls during foaling. Initial clinical signs
will depend on the scale and location of the bleed, and in particular whether the
vessel haemorrhages into a confined space. When a uterine artery bleeds into the
broad ligament or a vessel haemorrhages within the uterine wall, initial clinical signs
are primarily associated with abdominal pain whereas, if the vessel bleeds into the
abdominal cavity, the initial signs will be those of acute blood loss, e.g. a rapid weak
pulse, rapid shallow breathing, cold extremities and pale mucus membranes. In the
case of a bleed into the abdominal cavity, the diagnosis is often presumptive since
progression may be too acute to allow a full work-up. Moreover, the prognosis is
grave since even blood transfusion is generally inadequate to maintain perfusion and
oxygenation, while attempts to identify and ligate the bleeding vessel are unlikely to
succeed.
Haemorrhage within a closed space such as the broad ligament or uterine wall in a
mare presented with colic can be confirmed by per rectum palpation and
ultrasonography; in such cases, it is hoped that a clot will form and arrest the
bleeding. Further treatment is supportive and focused on pain relief, blood
transfusion if the packed cell volume is falling rapidly or is below 12 and still
decreasing, and keeping the mare in a quiet environment in the hope that the broad
ligament does not rupture and/or the haemorrhage does not dissect out through the
tissues of the uterus and vagina. Further circulatory support is provided only if
absolutely necessary because, while expanding the circulatory volume and raising
the blood pressure may aid perfusion and oxygenation, they can also interfere with
clot formation. Anti-fibrinolytic drugs such as aminocaproic acid are sometimes
recommended to assist clot stabilisation, but little is known about their efficacy in
horses (Frazer, 2003).
Uterine tear/rupture
Uterine tears can arise as a result of dystocia or the correction thereof, but can also
arise spontaneously during an uneventful foaling. The former are most often located
in the caudo-ventral uterine body, whereas spontaneous tears often occur in the tip
of the pregnant horn. Large, dystocia-related tears in the uterine body are often
associated with considerable haemorrhage, and emergency circulatory support may
be required to stabilize the mare while attempts are made to surgically close the tear
and arrest the bleeding through a vaginal approach. Smaller tears, particularly in the
tip of the uterine horn, may not present until two or more days after foaling when the
mare shows signs of peritonitis (colic, pyrexia, depression, abdominal defence). In
such cases, the affected uterine horn will usually be poorly involuted; however, the
tear may be difficult to locate per vaginam because of the length and pronounced
folds of the uterine horn. Moreover, hysteroscopic investigation is complicated by the
difficulty in inflating the post-partum uterus. On the other hand, a peritoneal tap is a
very useful part of the diagnostic work-up; obvious similarity in appearance and
odour of uterine and abdominal fluids is suggestive of a full thickness tear. While
large full thickness tears should be corrected surgically (laparotomy or laparoscopy),
Proceedings
of
the
South
African
Equine
Veterinary
Association
Congress
2016
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