Caslicks Procedure

The Caslick procedure of surgically closing the upper part of the vulva has been commonly practiced on broodmares for the past 60 years. The procedure evolved in an effort to treat what E. A. Caslick, DVM, had observed--the negative effect that air had on a mare's reproductive system.

"Early in my experience with the treatment of genital infections, I recognized air as a factor," Caslick wrote on the matter. "Mares that were placed on treatment (for genital infections) apparently became worse for a short period of time and then their condition remained quite constant. If these same mares were allowed a period of rest, an immediate improvement would be observed."

Caslick suspicioned that the treatment-related introduction of air into the reproductive system was doing more harm than the specific treatment was doing good.

"The last case of this infection, I (Caslick) encountered was in 1927. At that time, I became firmly convinced that the admission of air into the vagina by constant treatment was detrimental, so I discontinued treatment of the mare and closed the dorsal (upper) half of the vulvar opening (the first "Caslick's procedure"). In two months, this mare was normal and negative to culturing (for bacteria in the reproductive tract)."

In a 1937 volume of the Cornell Veterinarian, Caslick, a native of upstate New York and a graduate of Cornell's College of Veterinary Medicine, reported his surgical technique and the thought processes that lead up to the technique's development. Large parts of that original article will be quoted here as Caslick's writings give great insight from a veterinarian who, in addition to mastering the science, also (and perhaps more importantly) mastered the art of being a veterinarian.

Wind-sucking, or more technically pneumovagina, was generally accepted as a potential problem in all racing females.

"It has always been common knowledge to the breeders that a mare with an injury to the upper part of the vulva and rectum was frequently a 'wind-sucking' mare and a bad breeder. Most of them were permanently sterile, but such injuries affected only a small number of mares. It was not realized that the mare with a normal vulva might become a bad breeder or permanently sterile for the same reason as an injured mare."

When air enters the vagina it can bring in dirt, bacteria, and other debris. It is this contamination that can lead to vaginitis (inflammation of the vagina), cervicitis (inflammation of the cervix), and metritis (inflammation of the uterus).

The first barrier that protects the uterus from the outside world is the vulva. A defect in the vulva can allow contamination to enter the vagina. Abnormalities in the vulva can be from either previous trauma or deviations from normal anatomy. The second protective barrier is the cervix. The cervix is a circumferential muscular structure and in essence represents the junction between the vagina and uterus. During the heat period, the cervix is relaxed, allowing sperm to enter the uterus; in non-heat periods or during pregnancy, the cervix should remain tightly closed, protecting the uterus or developing fetus. Wind-sucking can lead to chronic inflammatory states in the vagina, cervix, and potentially the uterus that can reduce fertility. Wind-sucking during pregnancy can lead to abnormalities in the developing fetus or even abortion.

The causes and predisposing factors of pneumovagina are essentially unchanged since Caslick's original report.

"The mare may begin the habit of wind-sucking at any time, and apparently for no reason, but it usually follows some derangement of the genital tract," noted Caslick. "Wind-sucking most often follows injuries to the upper part of the vulva and rectum. Other factors involved are conformation of the vulva, age, atrophy of the tissues around the external genital tract, and constant relaxation of the vulva. Certain types of vulvae appear to favor the chances of a mare becoming a wind-sucker; the two most common being the near- or over-perpendicular and the partial horizontal."

These two vulvar conformations favor an incompetency of the vulvar lips. The first is reported to occur more commonly in maiden mares, and the second in older mares which have a sunken perineal region. In the partial horizontal, it appears as if the rectum has moved forward, pulling the upper part of the vulva with it; hence a mid-vulvar part that is horizontal. This conformation also can be associated with mares which are in very poor body condition. The vulvar abnormalities can be a predisposition, but Caslick pointed out that "wind-sucking may occur in any mare, none are exempt, not even the maiden or pregnant mare."

Wind-sucking can be obvious or subtle in mares.

"The most common symptom (sign) of wind-sucking is the gurgling noise or sound produced by the aspiration of air into the vagina, or its expulsion," Caslick observed.

Veterinary inspection can detect abnormalities in the lips of the vulva, an abnormal and persistent "state of relaxation" of the vulva, and/or the presence of air in the vagina as determined by rectal palpation. A small amount of foamy material in the vagina or the presence of a purulent (pus-containing) discharge that develops in a mare approximately five days after breeding is often associated with pneumovagina.

The "operation to prevent wind-sucking" as described by Caslick in 1937 went like this: "The vulva is cleansed; about half the lips and the upper commissure of the vulva are localized with anesthesia (local application of anesthetic to numb the tissue). The edges of the lips of the vulva are scarified (the skin and some subcutaneous tissue is removed with something sharp) to the depth of one-half inch. The two scarified surfaces are brought together and held in position by metal wound clamps or sutures."

The length of vulva sutured together depends on the individual needs of the mare. Caslick reported that, "Any time that the mare is found to be sucking air into the vagina, except in the normal-length heat period, the act should be stopped." He believed that this simple operation "saved the life of at least 15% of Thoroughbred broodmares."

The "fresh" edges of the vulvar lips heal together quite well and stay that way after suture removal in six to 10 days. The only remaining fact to point out is an obvious one: Now that the vulvar lips are closed, they will need to be opened before foaling and potentially before breeding if a substantial length of vulva was sutured; an episiotomy is performed when foaling is eminent and generally surgically closed within two to three days post-foaling unless there are complications.

About the Author

Michael Ball, DVM

Michael A. Ball, DVM, completed an internship in medicine and surgery and an internship in anesthesia at the University of Georgia in 1994, a residency in internal medicine, and graduate work in pharmacology at Cornell University in 1997, and was on staff at Cornell before starting Early Winter Equine Medicine & Surgery located in Ithaca, N.Y. He is also an FEI veterinarian and works internationally with the United States Equestrian Team.

Ball authored Understanding The Equine Eye, Understanding Basic Horse Care, and Understanding Equine First Aid, published by Eclipse Press and available at or by calling 800/582-5604.

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