Page 466 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Reproductive system: 2.1 The female reproductive tr act 441

VetBooks.ir Clinical presentation achieved in the last 30 days of pregnancy by admin-
istering oxytocin (see Induction of parturition,
Hydrops usually occurs in the pregnant mare in the
last trimester of pregnancy, with a rapid accumula-
of the cervix over a 15–30 minute period or by plac-
tion of fluid in the uterus leading to visible abdomi- p. 458). Abortion can be induced by manual dilation
nal enlargement over a few days to weeks (Fig. 2.42). ing dinoprostone (6 mg vaginal tablets) within the
In some severe or chronic cases the mare may have cervix for a few hours, after which the allantochori-
problems standing after recumbency, signs of breath- onic membranes can be manually ruptured through
ing difficulties, low-grade abdominal pain and, in the cervical os. Whether abortion or induction is
extreme cases, rupture of the ventral abdominal wall used, assistance with delivery of the foal is usually
or prepubic tendon. Secondary ventral peripheral required because of uterine inertia. It is important
oedema or inguinal herniation may occur, and uter- to control the drainage of fluid from the uterus in
ine rupture has occasionally been reported. order to minimise fluid imbalance and/or circulatory
shock in the mare, which can be fatal. A sterile naso-
Diagnosis gastric tube can be useful for siphoning out the fluid
Clinical signs and rectal palpation can confirm these and regulating the flow. Intravenous polyionic fluids
conditions, but transabdominal or transrectal ultra- or hypertonic saline may be useful during drainage
sonography may help differentiate hydrops amnion to help maintain blood pressure.
from hydrops allantois and detect abnormalities of After parturition or abortion, retention of pla-
the placenta and/or fetus. On rectal palpation the cental membranes is common and should be treated
uterus is massively enlarged, filling much of the cau- as soon as possible. Use of an oxytocin drip may
dal abdominal cavity and making it difficult to detect stimulate contractions and prevent uterine pooling
the fetus. If the foal is identified as being abnormal of blood within the splanchnic circulation. Uterine
(Fig. 2.43), treatment should be directed more involution and subsequent fertility are unaffected.
towards saving the mare.
Prognosis
Management Severe or chronic cases carry a guarded to poor prog-
Given that it is unlikely the mare will sustain the nosis for the mare, especially if abortion or parturition
pregnancy, the high risk of severe secondary mater- is not induced quickly and circulatory and/or ventral
nal issues and the high likelihood of fetal abnor- abdominal wall problems ensue. There are reports of
malities, it is recommended that the pregnancy is normal foals being born from mares with this condi-
terminated. Induction of parturition is most easily tion, but most are abnormal and non-viable.

2.42 2.43

Figs. 2.42, 2.43 (2.42) A late-pregnant mare showing gross abdominal enlargement due to a hydrops.
(2.43) After parturition the foal was found to be abnormal, with a hydrocephalus and grossly enlarged abdomen.
(Photo 2.43 courtesy Tracey Chenier)