Castration Of The Normal Horse

 

    Castration is probably the most common surgical procedure performed in male horses.

Castration is usually performed to prevent or eliminate aggressive male behavior in animals not intended to become breeding stallions.

Other indications for castration include:

Testicular neoplasia, testicular trauma, spermatic cord torsion, orchitis, periorchitis, Hydrocele, hematocele, and most  cases of inguinal or scrotal hernia.

Castration may be safely performed at any age.

Factors that influence the age at which castration is performed are the veterinarians personal preference, the owners wishes, and the potential breeding value of the animals.

Foals that are destined to become geldings may best be castrated before they are weaned.

Foals castrated at this age seen to recover from surgery more quickly and with fewer complications than older animals.

Some owners prefer delaying castration until  later age to allow for development of a more masculine appearance.

Horses with potential value as breeding animals are usually not castrated until after maturity, when performance has been fully evluated.

Castration can be performed safely and acceptably either with the horse standing, using chemical restraint and local anesthesia, or with the horse in recumbency under general anesthesia.

Factors for choosing one method or the other include the surgeon's preference, practice tradition, owner's desire, behavior of the horse, descent of the testicles, and location where the surgery will be performed.

 

J Standing castration:

Prior to castration a physical examination should be performed to determine if the animal is healthy.

The scrotal region should be palpated to determine if both testicles have descended and to evaluate for inguinal herniation.

Ideal candidates for standing castration are animals that allow genital palpation without sedation.

Horses that elicit a marked hostile or evasire response to genital palpation may best be casterated in recombancy under general anesthesia.

Standing casteration of small ponies and horses with poorly developed testicles is mechanically difficult.

 

J Anesthesia and surgical preparation:   

Standing castration is performed using chemical restraint and local anesthesia.

A number of sedative-hypnotic, tranquilizing, and opioid agent are available for chemical resistant in the horse and selection is based on personal preference.

Detomidine (0.011 to 0.022 mg /kg IV) in combination with butorphanol (0.011 to 0.022 mg/kg IV) provides excellent sedation analgesia for standing castration.

Following adequate sedation (4 to 8 minutes) local anesthesia is performed.

Following application of a lip twitch anesthesia of the testis and spermatic cord is accomplished by injecting 10 to 25 ml (depend on the size of the testicle) of local anesthetic into the parenchyma of each testicle using an 18 - to 20 gauge, 3 - 8 cm needle.

Anesthesia of the scrotal skin is achieved by subcutaneous infiltration of local anesthetic along each side of the scrotal raphae.

The horses tail should be warpped to prevent it from contaminating the surgical field.

The scrotum, inguinal region, and medial thighs should be scrubbed before and after administration of the local anesthetic.

 

J Surgical technique:

Standing castration should be performed with both the surgeon and handler postioned on the same side of the horse.

The right-handed surgeon stands on the left side of the horse, making body contact in the flank area.

Both spermatic cord are grasped with the left hand, and the testicles are displaced ventrally to tense the skin of the scrotum.

With a scalpel blade held in the right hand, longitudinal incisions are made over each testis, parallel and equidistant from the scrotal raphe and extending the full length of the testis.

Each incision is made in a craniocaudal direction through the skin , tunica dartos, and scrotal fascia, leaving the parietal vaginal tunica intact.

A longitudinal incision is then made through the vaginal tunic over the length of the left testicle, allowing the testicle to prolapse through the incision.

The mesorchium is then perforated to separate the vascular spermatic cord and ductus deference from the vaginal tunic.

This permit separate emasculation of the vascular spermatic cord and the vaginal tunic.

Emasculation of the vaginal tunic first eliminates the pull of the cremaster muscle on the testicle.

The procedure is then repeated on the right side (testicle).

The emusculator should be placed distally around the tissue to be severed, loosely closed and slid proximally to the site of eventual transection.

Care must always be taken to ensure that the emasculator has been applied correctly so that the crushing component is proximal to the cutting blade.

Failure to do so can result in severe or fatal haemorrhage.

The emusculator should be applied at right angles to the tissue to be divided, and the jaws should be inspected to ensure that they do not contain scrotal skin.                         

Tension on tissue should be released during transection, and the emusculator should remain in place for 1 to 2 minutes.

The vascular spermatic cord or large adults or mature breeding stallions may be ligated with a transfixation ligature and then emusculated distal to the ligature.

Following removal of both testicles, any fascia protruding from the incision is excised.

The wounds are left open to heal by second intention.

If the horse begins to resist manipulation at any time during the procedure, additional chemical restraint should be administered.

J Postoperative management :

The tetanus immunization history for each patient should be determined.

Horses not previously vaccinated for tetanus should receive tetanus antitoxin and tetanus toxid.

Horses previously immunized against tetanus should receive aboster if more than 6 months has passed since the last vaccination.

Horses should be confined to a clean stall for 12 to 24 hours after surgery and observed closely for hemmorhage or evisceration.

Thereafter, the horse should be force-exercised at least 15 minutes twice daily until healing is complete.

Horses turned out on pasture should be checked daily to ensure that they are exercising sufficiently to controle postoperative edema.

Routine administration of antibiotics and nonsteroidal anti inflammatory drugs has not been recommended.

It is commonly administers phenylbutazone (2.2 mg/kg, twice daily for 3 days) and procain penicillin G (22.000 u/kg I/M , twice daily for 3 days) to horses castrated at 2 years of age or older.

J Recumbent castration:

Indications for castration in recombency under general anesthesia include personal preference, owner's request, fractious animals small ponies, and horses with poorly developed or inguinal testicles.

A requirement for recumbent castration is a clean, safe area for induction and recovery from anesthesia.

Prior to castration, a physical examination should be performed to ensure that the animal is healthy.

The scrotal region should be palpated to determine that both testicles have descended and to evaluate for inguinal herniation.

Fractious animals may need to be sedated to allow adequate palpation.

Ideally, grain and hay should be with held from the horse for 12 hours before surgery.

J Anesthesia and surgical preparation:

Short - term general anesthesia for recumbent casteration can be safely induced and maintained with a variety of injectable drugs.

The most commonly used anesthetic drugs for recumbant castration of horses is a combination of xylazine and ketamine.  

Xylazine is administered first at 1.1 mg/kg IV.

Only following the onset of adequate sedation (2 to 4 minute) 2.2 to 3.0 mg/kg of ketamine is administered intravenously.

This protcol results in recumbency in 1 to 2 minutes and provides 10 to 15 minutes of surgical anesthesia.

The administration of butorphanol (0.022 to 0.044 mg/kg IV ) simultaneously with or just after xylazine administration may provide additional analgesia and muscle relaxation.

If additional time is required to complete the surgical procedure, anesthesia may be safely prolonged by administering one-third to one- half of the original dose of xylazine and ketamine intravenously.

Following induction of anesthesia, the horse is positioned in lateral recumbency, and the upper hind limb flexed and pulled forward by a robe tied or held by an assistant.

For right-handed operators, castration is most easily performed with the horse in left lateral recumbency.

The scrotum, prepuce, and inguinal region are throughly scrubbed.

J Surgical technique:

The surgeon should stand behind the horses croup and reach over to the operative field.

The lower testicle is tensed in the scrotum with the left hand and a skin incision is made over the greater curvature of the testicle for the length of the testis.

The incision is continued through the tunica dartos and scrotal fascia, leaving the parietal vaginal tunic intact.

At the same time, pressure exerted by the thumb and fore finger of the left hand causes the testis within the vaginal tunic to be extruded.

A 3 to 4 cm longitudinal incision is then made through the vaginal tunic over the cranial pole of the testis.

The right thumb is inserted through the incision and ventral traction is applied while fingers of the right hand prolapse the testicle through the incision.

During this maneuver the right index and midle fingers are hooked into the inverted vaginal tunic.

This provides a firm handle for further manipulation and balances the pull of the cremaster muscle.

The scrotal fascia is then stripped from the vaginal tunic in a proximal direction with the left hand.

The use of a gauze sponge facilitates the stripping process.

The incision in  the vaginal tunic is than extended proximally with scissors, allowing observation of all enclosed structure (testicle, epidermis, ductus deferens, spermatic vessels) an inspection for the presence of intestine or omental tissue.

Young horses or horses with relatively small spermatic cord may be safely emasculated across the entire spermatic cord.

In mature horses or will develop young horse the mesorchium can be penetrated to separate the vascular spermatic cord and ductus deferens from the vaginal tunic.

This permits separate emasculation of the vascular spermatic cord and the vaginal tunic.     

Emulsculation of the vaginal tunic first eliminates the pull of the cremaster muscle on the testicle.

Alternatively, the entire spermatic cord or vascular spermatic cord may be ligated with a transfuxation ligature and then emasculated distal to the ligature.

Care must always be taken to ensure that the emusculator has been applied correctly so that the crushing component is proximal to the cutting blade, (cutting blade closest to the testicle).

Failure to do so can result in severe or fatal hemorrhage.

The emusculator should be applied at right angles to the tissues to be divided, and the jaw should be inspected to ensure that they do not contain scrotal skin.

Tension on the tissues should be released during transection, and the emusculator should remain in place for 1 to 2 minutes.

The procedure is then repeated on the upper testicle.

The wound are left open to heal by second intention.

Any fascia protruding from the incision site, after the horse stand should be trimmed with scissors.

J Postoperative management

Postoperative management of horses undergoing recumbent castration is the same as far horses undergoing standing castration.

J Castration with primary closure:

Traditionally, castration wounds have been left unsutured to heal by second intention.

However, techniques of primary closure with or without scrotal ablation have been developed and used successfully to castrate horses.

Primary closure enables wound healing to proceed quicker with less chance of secondary bacterial infection.

The most successful techniques appear to involve isolation of the testicle with or without prior placement of transfixation ligature.

Scrotal ablation and closure of the deeper fascid layers may be performed to reduce dead space.

Although castration with primary closure may be ideal, it probably not practical for field castration-surgery time is longer than most field anesthetic regimens supply, and strict adherence to aseptic technique is required.

J Complications of castration:

Complications associated with castration represent one of the major categories of malpractice claims in the equine practice.

The most commonly encountered complication, include infection and hemorrhage.

Less frequently encountered complications include evisceration, penile damage, hydrocele, and accidents associated with physical restraint and general anesthesia.

The incidence of these complications can be minimized by careful planning by the surgeon.

Horses should be kept under close observation for at least the first 24 hours because this period is when the most serious complications are likely to occur.

J Hemorrhage:

Excessive hemorrhage is the most common immediate postoperative complication of castration.

The most likely source of excessive hemorrhage is the spermatic vessels.

Hemorrhage from the spermatic vessels may result from improper application of the emusculator or the use of an inferior or malfunctioning emusculator.

Upside - down application of the emusculator results in severe hemorrhage because the spermatic vessels are cut proximal to the site of the crush.

Incorporation of the scrotal skin in the jaws of the emusculator may result in insufficient crush of the spermatic vessels.

Oblique transection of the spermatic cord increasse the diameter of the served end of the spermatic vessels and increases the likelihood of hemorrhage.

In mature stallions or well - developed young horses with large spermatic cords, separate emusculation of the vascular spermatic cord and vaginal tunic may be required for adequate hemostasis.

Hemorrhage may also occur from scrotal vessels that are lacerated during the incision or when excising scrotal fascia. This hemorrhage is usually not serious and stops spontaneously.

The scrotum and the stump of the spermatic cord should be examined to locate the source of hemorrhage.

Bleeding scrotal vessels should be clamped and ligated. If the hemorrhage is coming from the spermatic vessels, a long hemostatic forceps can often be used to grasp the end of the transected cord. The forceps should remain in place for 12 to 24 hours.

If the source of hemorrhage cannot be located and controlled  in  the standing horse, exploration under general anesthesia is indicated.

Severe blood loss may necessitate volume replacement with intravenous fluids or whole blood.

Cross - matched whole blood administered at 15 to 25 ml/kg is the treatment of choice for severe blood loss. Or hypertonic saline (4 ml/kg 7 % Nacl) followed by isotonic crystalloid fluids.

J Infection:

Mild scrotal and preputial edema is expected following castration and is controlled by ensuring adequate postoperative exercise.

Excessive edema accompanied by a fever indicates infection of the castration wounds.

Infection of the scrotal wounds is the most common complication following routine castration.

Factors such as premature sealng of the open casteration wounds, retained blood clots, contamination, use of ligatures, and poor surgical technique increase the occurence of wound infection. In addition, it is believes that wound infection are common in horses castrated at/over 2 years of age.

Treatment should include reestablishing drainage from  the scrotal wounds and the administration of systemic antibiotics such as procaine penicillin G.

The administration of a nonsteroidal anti-inflammatory drug such as phenylbutazone is indicated to reduce edema and soreness.

Hydrotherapy of the scrotal wound may assist in keeping the wounds open and clean.

Infection of the spermatic cord may occur as a result of contamination during surgery or from extension of scrotal infection.

** Infection of the spermatic cord with streptococcal organisms is referred to as "champignon".

Clinical signs of spermatic cord infection include scrotal swelling, fever and inflammation and induration of the spermatic cord.

Early or mild cases of spermatic cord infection usually respond to systemic antibiotic administration and proper scrotal drainage. However, surgical removal of the infected spermatic cord may be necessary in some cases.

** Chronic, low - grade, staphylococcal infection of the spermatic cord has been referred to as "Scirrhous cord".

The condition is characterized by multiple small abscess surrounded by extensive fibrous tissue.

The condition may not become clinically apparent for months to years after castration.

Successful treatment requires complete surgical removal of the affected tissue.

Extension of scrotal or spermatic cord infection into the peritoneal cavity is a rare but potentially serious complication of castration in horses.

Signs of septic peritonitis include fever, depression, colic, tachycardia, hemo-concentration, weight loss, reluctance to move and diarrhea or constipation.

Suspecion of septic peritonitis warrants collection and evaluation of peritoneal fluid. However, results of peritoneal fluid analysis must be interpreted.

Peritoneal nucleated cell counts of > 10.000 / Ml are common for 5 or more days following uncomplicated castration, and occasionally cell counts of > 100.000 / Ml are encountered.

A diagnosis of septic peritonitis should not be based only on the presence of a high nucleated cell count, but also on the presence of toxic or degenerative neutrophils intracellular bacteria in the peritoneal fluid.

Treatment of septic peritonitis includes administration of systemic antibiotics based on culture and sensitivity result, supportive therapy, and possibly abdominal lavage.

In some instance, resection of an infected spermatic cord may be required.

J Evisceration:

An uncommon but potentially fatal complication of castration is herniation of small intestine through the vaginal ring and open scrotal incision.

Intestinal evisceration has also occurred where the scrotal wound was closed primarily but the vaginal tunic had not been closed.

Factors such as preexisting inguinal hernia, recovery from general anesthesia, and postoperative rearing have been incriminated in  the development of evisceration.

Evisceration usually occurs within the first 4 hours after surgery, but has been reported up to 6 days postoperatively.

As soon as intestinal evisceration is observed, immediate measures need to be taken to prevent further prolapse and to reduce contamination and damage.

If only a short length of the intestine has prolapsed, it may be able to be reduced into the scrotum and maintained with towel clamps or sutures.

Large prolapses may be supported and protected by moistened towels fashioned into a sling. 

The horse is anesthetized and positioned in dorsal recumbency.

The prolapsed intestine should be cleaned and throughly lavaged with a balanced electrolyte solution.

The ventral abdomen and inguinal area are prepared for surgery.

If the bowel is healthy and relatively uncontaminated, it should be replaced into the abdomen. Aspiration of intraluminal gas may also facilitate intestinal reduction.

Significcantly compromised bowel necessiates resection and anastomosis. The vaginal ring may need to be enlarged so that a portion of normal bowel can be exteriorized.

If sufficient normal intestine cannot be exteriorized, the prolapsed bowel may be blind ended and resected with an intestinal stpling device, oversewn with suture, and then replaced into the abdomen.

Anastomosis may then be performed through a ventral midline laparotomy.

In an attempt to prevent reevisceration, the spermatic cord should be closed with a transfixation ligature if possible, and the external inguinal ring should be closed also.

Omental evisceration may also occur in horses following castration. When this is noted, a rectal examination should be performed to ensure that intestine has not entered the inguinal canal as well.

Ideally, the horse should be placed under general anesthesia, the prolapsed omentum cleaned, and the scrotal - inguinal area are prepared for surgery.

The parietal vaginal tunic is incised exposing the prolapsed omentum and the vasular spermatic cord stump. The omentum is ligated and transected distally and then replaced into the abdomen.

The spermatic cord is then closed with a transfixation  ligature  and transected distally.

The distal portion of the spermatic cord and omentum is then removed via the scrotal wound.

Successful management of omental prolapse may also be achieved by simple transection of the exposed omentum as proximally as possible with an emasculation. This may be performed on the standing or recumbent animals.     

No attempt is made to replace the omentum into the abdomen.

It is possible to reduce the incidence of post castration evisceration by identifying high - rise patients by obtaining an accurate history and performing a through preoperative physical examination.

Horses with:

1- A history of an inguinal hernia as a foal.

2- Siblings or relatives with histories of inguinal herniation or evisceration.

3- Un explained hind limb lamness or back pain.

Physical findings of inguinal or scrotal swelling are candidates for recumbent castration with transfixation ligatures of the spermatic cord and closure of  the external inguinal rings.