LAPAROSCOPIC OVARIECTOMY: New alternative for hormone-related behaviour in mares
Jennifer Lansdowne, Ludovic Bouré and Simon Pearce Department of Clinical Studies Ontario Veterinary College University of Guelph, Guelph

Ovariectomy is a surgical procedure performed to remove one or both ovaries. In horses, bilateral ovariectomy is done as an elective surgery in mares that are not going to be used for breeding purposes. An indication for ovariectomy in mares is to prevent estrus-associated behaviour. In these cases, undesirable behaviour occurs when the mare is in estrus and includes frequent posturing and urination, striking, kicking, difficulty under saddle and other dangerous or undesirable vices. Mares that respond to progesterone therapy are likely to respond to ovariectomy and removal of both ovaries is indicated in these cases. In addition to behavioural concerns, ovariectomy may be requested for registration purposes or for mares to be used for semen collection. It is also ecommended in mares that are carriers of a detrimental genetic condition in order to remove the defect from the breeding population (such as severe combined immunodeficiency syndrome in Arabian horses).

Ovariectomy in mares was first described before the twentieth century and involved the use of an écraseur (crusher) via colpotomy (vaginal approach). Unfortunately, this technique is associated with a high rate of potentially fatal complications. The standard technique at present (laparotomy) involves large abdominal wall incisions (at least 20 to 30 cm long). These large incisions require that the mares be rested several weeks to months after the surgery in order to allow complete healing. Recently, laparoscopic ovariectomy techniques have been developed in mares. Laparoscopy is a surgical technique that uses a rigid endoscope to view the organs within of the abdominal cavity. Laparoscopy uses specially adapted instruments to allow surgery within the abdomen to be performed from outside the body, thus requiring very small incisions. Laparoscopy is extremely popular in human surgery, particularly for gall bladder and appendix removal. Humans experience very small incisions, minimal post-operative pain, and can be discharged a few hours after surgery. The use of laparoscopy in horses is a more recent development, but the advantages are the same. (i.e. very small incisions, minimal postoperative pain, and a quick return to exercise).

Laparoscopic ovariectomy can be performed with the horse standing, or under general anaesthesia. The method used depends on the mare’s temperament and the surgeon’s preference. In both approaches, the ovary is located, tied off using laparoscopic ligatures, cut from the ovarian pedicle, and removed through one of the small incisions in the body wall. Laparoscopy permits excellent observation to perform the surgery. The largest incision required in the mare will be one that is just large enough to remove the ovary (normally about the size of a golf ball). Normal sized ovaries are therefore best removed using this technique; however, even with slightly enlarged ovaries the incision will be much smaller than that required when performing ovariectomy via laparotomy. After removal of the ovaries, the abdomen is deflated, the incisions are sutured closed and the horse is recovered from anesthesia. Following surgery, mares are observed for pain and complications. Pain is generally minimal, especially compared to procedures requiring large incisions.

Laparoscopic ovariectomy is a minimally invasive surgery. For this reason it can be highly beneficial for horse owners because mares can return to training two weeks after surgery. Standing laparoscopic ovariectomy of normal ovaries has the added benefits of being a rapid procedure that is relatively inexpensive for the client due to the reduced anesthetic costs. Cost of equipment and training are currently the main disadvantages of laparoscopic ovariectomy. However when the instrumentation and expertise is available, laparoscopy is a superior technique compared with laparotomy for ovariectomy in the mare.

The Research Team:
(left to right) Dr. Carolyn Kerr develops anesthetic techniques for laparoscopy at the OVC. The research team, headed by Dr. Ludovic Bouré, also includes Dr. Simon Pearce and Masters student Jennifer Landsdowne.

The Ontario Veterinary College at the University of Guelph currently offers ovariectomy by laparoscopy as well laparoscopic cryptorchidectomy (laparoscopic removal of testis retained within the abdomen). Several additional surgical procedures are currently being developed including laparoscopic removal of infected umbilical structures, laparoscopic repair of ruptured bladders and laparoscopic treatment of abdominal adhesions.

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Updated: October 2005.