Page 506 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Reproductive system: 2.1 The female reproductive tr act 481

VetBooks.ir DELAYED UTERINE INVOLUTION Diagnosis
The vagina tilts downwards on vaginal examination
Definition/overview
Post partum the uterus usually contracts markedly with, or without, urine pooling and vaginitis. The
uterus is flaccid and voluminous on rectal examina-
within the first few days, expelling a brown discharge tion. Hyperechoic intrauterine fluid is seen on ultra-
(lochia) from the vulva for 3–7 days and decreasing in sound examination.
size to its pre-gravid state. Histologically, the endo-
metrium returns to the non-pregnant state at approxi- Management
mately 14–15 days. In delayed involution the uterus The intrauterine fluid should be removed by lavage
fails to involute in the normal time frame, remaining using large volumes of dilute saline/povidone–iodine
flaccid, voluminous and fluid-filled. Recognition of solution. Oxytocin by intravenous or intramuscular
delayed involution can be a critical factor in deciding injection (15 IU) stimulates uterine contractions and
whether to mate a mare on the foaling heat. involution. Parenteral antibiotics and antiendotoxic
therapy may be necessary if systemic signs are pres-
Aetiology/pathophysiology ent. Paddock exercise is helpful. There is no evidence
Delayed uterine involution most commonly follows that prophylactic oxytocin or uterine lavage in the
abortion, dystocia, retained fetal membranes, pla- early post-partum period promotes involution or
centitis, uterine infection or haemorrhage, or lack of prevents failure of involution.
exercise.
Prognosis
Clinical presentation Good if treatment is implemented promptly,
Often there are no clinical signs, but occasionally although breeding may have to be delayed until the
there is an increase in vulval discharge. In unusual second or third oestrus following foaling.
cases the mare may be dull, have a poor appetite and
show abdominal discomfort.

DISORDERS AND DISEASES OF THE OVARY AND OVIDUCT

CHROMOSOMAL ABNORMALITIES internally and externally (e.g. ovarian/uterine hypo-
AND DISORDERS OF SEXUAL plasia) and infertility. The abnormality arises during
DEVELOPMENT OF THE MARE embryogenesis (mitosis) or gamete formation (meio-
sis). They are a particular problem when mares are
Definition/overview bought for breeding without a veterinary breeding
Horses have 64 autosomes and two sex chromo- examination, as detailed internal examination by
somes (XX for a mare, XY for a stallion). The most palpation and ultrasound may be necessary to iden-
common sex chromosome abnormality is 63XO, the tify the abnormal anatomy. The most commonly
equivalent to Turner’s syndrome in humans. It is reported disorder of sexual development (DSD) in
not unusual for chromosomal abnormalities to go horses is 63XO; others include mosaics (where two
unnoticed as it is generally only if the mare is bred different cell populations exist within the same
or examined for breeding that she will be identified. animal – e.g. 64XX/63X and 63X/64XX/65XXX),
Definitive diagnosis requires a karyotype on a blood gene deletions and SRY (sex-determining region on
sample. No treatment is available. the Y chromosome) abnormalities. All breeds can be
affected.
Aetiology/pathophysiology
Chromosomal abnormalities are usually associ- Clinical presentation
ated with abnormalities of the sex chromosomes Mares generally present at breeding or pre-breeding
and often lead to abnormal female genitalia, both examinations, or because of infertility, subfertility,