Fluid-filled structures of endometrial uterine cysts can be an impediment to fertility. Not only might they interfere with sperm transport to the fallopian tubes, but cysts also can impede embryonic migration through the uterus in the initial phases before implantation. Non-maiden mares greater than 10 years of age have a greater risk of developing uterine cysts than younger mares.
In an Italian study, researchers proceeded with a new technique on eight mares, aged 13-21 years [Carluccio, A.; Gloria, A.; Mariotti, F.; et al. Ethanol sclerotherapy for the treatment of uterine cysts in the mare. Journal of Equine Veterinary Science, April 2018, vol. 63; pp. 27-29]. These mares had remained open for two seasons despite appropriate natural or AI breeding attempts with fertile stallions. Based on uterine bacterial culture and biopsy, none of the mares had other fertility issues, such as bacterial endometritis.
All of the cysts were identified at the junction of the uterine horns and the body, with three-quarters of them located at the base of the right uterine horn. Most were 4 - 6 cm in size carrying 40-120 ml of fluid. Via hysteroscopy, puncture by an 18-gauge needle drained fluid from the cystic cavities. Each emptied cystic cavity was then injected to 40% capacity with 70% ethanol in saline in a process termed ethanol sclerotherapy.
Breeding via artificial insemination commenced on the second cycle post treatment. All the mares conceived by this second or third cycle following treatment, although breeding of one mare was delayed until the following year due to treatment late in the season. While this one mare did get bred, conceive and carry a foal to term the next season, she was not considered in the final analysis of this study. The results conclude that 87.5% of treated mares had an embryonic vesicle on ultrasound exam at Day 14.
Previous attempts at resolving uterine cysts have used laser ablation techniques through hysteroscopy, but that has been fraught with complications and a potential for uterine wall perforation and peritonitis. This newer sclerotizing procedure using ethanol only removes the inner layer of the cyst and creates vessel thrombosis followed by fibrosis. In these eight mares, there was no recurrence of cysts. Following treatment, fertility recovered to 87.5%. All the mares carried the foals to term without complications.
Such success using ethanol sclerotherapy indicates that uterine cysts might contribute to infertility, and that this method is safe and successful in resolving this particular fertility issue.