Mares in estrus can be challenging—and even dangerous—to deal with. So some owners seek a veterinarians’ help to control their mares’ estrous cycles and reduce estrus-related behavior. One of those methods involves placing a marble in the mare’s uterus, which essentially keeps the mare from cycling.

While veterinarians have noted no significant uterine problems during treatment with this technique in the past, they recently encountered what they believe to be a significant complication. Jessica Klabnik-Bradford, a veterinary student at the Kansas State University (K State) College of Veterinary Medicine; Maria Soledad Ferrer, DVM, MS, Dipl. ACT, clinical associate professor of theriogenology at K State; and a team of veterinarians from the college recently presented the case in a poster at the 2013 Society for Theriogenology Conference, held Aug. 7-10 in Louisville, Ky.

Intrauterine marbles help suppress estrus by extending the mare’s natural corpus luteum (the structure formed after the follicle releases the egg, or ovulates, and then produces progesterone) function. When veterinarians place a glass marble in the mare’s uterus, pregnancy recognition occurs and estrus is suppressed due to the corpora lutea’s persistent function. Mares return to estrus after the marble is removed.

In the current case, a 16-year-old Appaloosa mare who had no reproductive history presented to K State with a foul-smelling suppurative (pus-producing) vulvar discharge, Klabnik-Bradford said. Suspecting pyometra (infection of the uterus), endometritis (inflammation of the uterine lining), or vaginitis (inflammation of the vagina), veterinarians performed transrectal ultrasound to further explore the problem