Uterine Lavage in Mares (Female Horses): Indications and Technique

Uterine lavage in mares is a therapeutic procedure involving the infusion and subsequent drainage of sterile fluids—typically warm saline or lactated Ringer’s solution—into the uterus.

This technique aims to remove accumulated fluids, inflammatory debris, and infectious agents, thereby enhancing uterine health and fertility.

Indications

• Removal of intrauterine fluid and inflammatory debris after breeding.
• Treatment of post-breeding endometritis in mares with delayed uterine clearance.
• Enhancement of uterine contractility to assist fluid expulsion.
• Support antibiotic therapy by cleaning the uterine environment.
• Management of mares with large post-breeding fluid accumulations (>2 cm depth).
• Adjunct to oxytocin or prostaglandin treatment for impaired uterine clearance.

Technique

The technique of uterine lavage involves the mechanical suction or siphonage of 2-3 litres of previously warmed (to 42°C), sterile physiological (buffered) saline or lactated Ringer’s solution infused into the uterus via a catheter that has been retained within the cervix via a cuff.

The most convenient is a large-bore (30 French) (80 cm) autoclavable equine embryo flushing catheter. The cuff is useful as it effectively seals the internal cervical os.

The catheter should only be inserted after thorough cleansing of the perineum. The rationale for such an approach is :

• To remove accumulated uterine fluid and inflammatory debris that may interfere with neutrophil function and the efficacy of antibiotics.
• Stimulation of uterine contractility.
• Recruitment of fresh neutrophils through mechanical irritation of the endometrium.

The saline is infused by gravity flow 1 litre at a time, and the washings are inspected to provide immediate information concerning the nature of the uterine contents. The lavage should be repeated until the fluid that is recovered is clear.

In most cases, the fluid is evenly distributed in both horns, making transrectal massage of the uterus unnecessary. If a rectal examination is performed whilst the catheter is in the uterus care must be taken to avoid contaminating the catheter.

The fluid should be recovered in the same container from which it was infused, thereby preventing air being aspirated into the uterus via the catheter. Measurement of the recovered fluid and ultrasonographic examination of the uterus should be performed after flushing to ensure that all the fluid has been recovered. This is necessary because you are dealing with a mare with an impaired ability to drain the uterus spontaneously.

For this reason the process is usually combined with oxytocin injection. Ideally these mares will be bred only once, but if repeated matings are necessary, uterine lavage should be performed after each mating.

Large-volume lavage is beneficial in many cases, particularly the mare with a relatively large (above 2 cm depth) accumulation of fluid after breeding. The process is time-consuming and there is the possibility of further contamination of the uterus by passage of a drainage tube.

Oxytocin

The ideal method of treatment will be the use of a non-invasive technique with early and complete elimination of any intrauterine fluid.

Oxytocin stimulates uterine contractions in the cyclical, pregnant and postpartum mare and hence can be used as a method to promote uterine drainage in mares with defective uterine clearance. However, its use was discouraged because of the worry that it would cause severe colic.

Prostaglandin Analogues

Prostaglandin analogue cloprostenol given at a dose rate of 500 µg IM increased myometrial activity and assisted in uterine clearance. Of the prostaglandins administered (PGF2 α, cloprostenol and fenprostalene) cloprostenol produced the most consistent response.

Cloprostenol would seem to be indicated in mares that have lymphatic stasis as shown by excessive fluid within the endometrium or large lymphatic cysts. Cloprostenol should not be given more than 24 hours after ovulation in case of inducing premature luteal regression

Intrauterine Plasma Infusions

Intrauterine plasma has been used in the susceptible mares and had an enhancing effect on phagocytosis by uterine neutrophils.

However, its use may only apply to mares without a mechanical clearance problem and thereby repeatedly fail to become pregnant, but have no history of fluid accumulation.