Urovagina in Horses: Urine Pooling, Infertility, and Mare Management

Urovagina is a condition in which urine pools in the vagina of a mare instead of draining away normally. It may happen only at certain times, such as during estrus when the cervix is relaxed, or it may become a chronic problem in mares with poor reproductive tract conformation. Merck notes that a definitive diagnosis requires direct observation of urine in the vagina during vaginoscopy.

This matters because urine is irritating to delicate reproductive tissues. Over time, pooled urine can inflame the vaginal lining and may contribute to chronic uterine irritation, vaginitis, endometritis, and infertility. Some mares also develop urine staining on the tail and inner thighs, an abnormal voiding pattern, or discomfort around the vulva.

Urovagina is most often discussed in broodmares, especially older mares or mares after foaling injuries, because fertility is usually the main concern. Still, even a mare not intended for breeding can need care if urine pooling is causing irritation, discharge, odor, or recurrent infection. Your vet can help sort out whether the issue is mild and manageable or whether surgical correction is likely to improve comfort and reproductive success.

Urovagina usually develops because the mare's anatomy no longer keeps urine and outside contaminants moving in the right direction. Poor perineal conformation, loss of vulvar seal, a sloped or sunken anus, and weakness of the vestibulovaginal fold can all make it easier for urine to reflux into the vagina. Merck also notes that urine may be present transiently during estrus or chronically when conformation is poor.

Older, thin, or multiparous mares are often at higher risk because repeated foaling, age-related tissue stretching, and loss of body condition can change the angle and support of the reproductive tract. Trauma from foaling can also damage the tissues that normally help separate the urinary and reproductive passages.

In some mares, urovagina overlaps with pneumovagina, where air is aspirated into the reproductive tract because the vulvar seal is not tight. That combination can worsen irritation and contamination. The result is not always dramatic at first, but over time it can create an environment that is less favorable for conception and early pregnancy.

Because several reproductive problems can look similar, your vet will also consider other causes of infertility or discharge, including vaginitis, endometritis, cervical problems, and poor breeding timing. That is why a full breeding soundness evaluation is often more useful than treating the visible urine pooling alone.

Diagnosis starts with history and a careful reproductive exam. Your vet will look at the mare's perineal conformation, vulvar seal, and any urine staining on the tail or inner thighs. In breeding mares, Merck recommends a complete breeding soundness examination that can include palpation and transrectal ultrasound, manual vaginal examination, and visual vaginal examination with a speculum.

The key test is vaginoscopy, because direct visualization of urine in the vagina is what confirms urovagina. Ultrasound may help show fluid in the vagina behind the cervix and can also assess the uterus and ovaries. Your vet may examine the mare during estrus and diestrus because the amount of pooling can vary with the stage of the cycle.

If fertility is the concern, your vet may also recommend uterine culture, cytology, and sometimes endometrial biopsy. These tests help determine whether urine pooling has already led to inflammation or infection and whether the uterine lining still has a reasonable chance of supporting pregnancy. In more complicated cases, referral to an equine reproduction specialist can be very helpful.

This is one of those conditions where the anatomy matters as much as the lab work. A mare can have mild urine pooling with acceptable fertility, while another with more severe conformational change may need surgery to have a realistic chance of carrying a foal.

Not every case can be prevented, especially in older mares or mares with significant post-foaling conformational changes. Still, early attention to reproductive anatomy can reduce the chance that mild problems become chronic ones. Regular breeding soundness exams are especially helpful for mares with a history of infertility, difficult foaling, urine staining, or repeated uterine inflammation.

Maintaining healthy body condition can also matter. Very thin mares may lose soft tissue support around the perineum, which can worsen poor vulvar seal and urine reflux. Good postpartum care is important too, because trauma after foaling can change the shape and function of the reproductive tract.

If your mare has poor vulvar conformation, your vet may recommend preventive management before breeding season, such as close monitoring, treatment of any uterine inflammation, or a Caslick-type procedure when appropriate. These steps do not prevent every case of urovagina, but they can reduce contamination and improve the reproductive environment.

The biggest preventive step is not waiting through multiple failed breedings. When urine pooling is caught early, your vet has more options to protect the uterus, improve comfort, and build a plan that fits your mare's future use.