6 Equine Castration

• Equine castration is a procedure performed by Dylan Lutter DVM, MS, DACVS-LA at Kansas State University.

Learning Objectives

• Know the technique and indication for open and closed castration
• Recognize and know how to manage the common complications of castration
• Reference Equine Surgery 5th Edition p 994-1034 for further information

Anatomy: The Testes

• Covered by the scrotum.
• Testicle is a key component.
• The epididymis has a head and body with a testicular bursa
• It also has a tail with connecting ligaments to the vaginal tunic.
• The spermatic cord includes the ductus deferens and the testicular artery and vein (pampiniform plexus).
• The cremaster muscle is also part of the anatomy.

Anatomy: The Vaginal Tunic

• Extension of the peritoneum
• Visceral tunic contacts the testicle, spermatic cord and epididymis.
• Parietal tunic lines the scrotal cavity and inguinal canal.
• Vaginal ring is a palpable internal opening to the inguinal canal.
• Vaginal process includes both tunics traveling through the inguinal canal.
• Vaginal cavity is the space between the two tunics and equates to the peritoneal cavity and communicates with it.
• Intestine could herniate into the scrotum, resulting in evisceration post castration

Anatomy: The Inguinal Canal

• External Inguinal Ring: Slit in the EAO and directed craniolaterally.
• Internal Inguinal Ring is directed dorsolaterally with cranial border caudal edge of IAO.
• Ventromedial border of Internal Inguinal Ring: rectus abdominus/prepubic tendon.
• Caudal border of internal Inguinal Ring: Inguinal ligament.
• External pudendal vessels and genitofemoral nerve pass caudally.
• Spermatic cord/testicle passes cranially.

Timing of Castration

• Owners often dictate the timing of the procedure.
• Can be based on "the signs" or the moon, or weather (heat vs. cold).
• Ranchers may wait until after the first freeze.
• It is often after weaning, especially if there are no facilities to separate stallions.
• Can wait until 4 years to allow for masculine characteristics.
• Racehorses are not castrated until they have proven to have no ability.

Pre-Op Considerations

• Location and conditions: Farm vs. hospital and inside vs. outside, considering weather conditions
• Ensure two palpable/visible testicles.
• Check tetanus vaccine status (vaccine vs. anti-toxin).
• Ensure an adequete stock of anesthetic medications.
• Consider antibiotics, with peri-operative use becoming more standard.
• Availability of pain medications is essential.

Tetanus Considerations

• Tetanus Toxoid requires an initial dose followed by a booster 4 weeks later, with a single dose not being protective.
• The first dose can be given at the time of castration.
• Tetanus Anti-Toxin: give antibodies to the tetanus toxin.
• Administer only if colt is not fully vaccinated at the time of castration; can be given at the same time as a tetanus toxoid vaccine.

Location of Surgery

• Choose wisely: Level, clean & open area with plenty of room for induction & recovery.
• Consider outside temperature.
• Surgery site should be out of the wind, dust, and away from farm activities.
• Be close to the truck/supplies.

Anesthesia and Positioning

• Anesthesia protocol should include a single dose of injectable drugs with backup drugs drawn and ready
• Backup is typically 50% of induction doses
• Common Anesthetic medications: Xylazine / ketamine +/- midazolam/diazepam
• Placement of an IV catheter can be considered.
• Positioning: Lateral recumbency with a leg tied up is best for solo/minimally assisted procedures.
• Dorsal recumbency is an option with pads &/or assistants to hold.

Additional Considerations

• Confirm the horse has two testicles before surgery:
• Check for presence of a scrotal hernia.
• Do not remove the down testicle if only one is descended.
• Check for and address an inguinal hernia: Bowel herniating through the inguinal rings within the vaginal tunic
• Hernia should be reducible and not preclude moving forward with closed castration; ligation is a must.
• Some clinicians close the external inguinal ring.

Standing vs. Recumbent

• Personal preference, local or breed custom, and surgical setting/temperament of the horse influence the choice.
• Weather is a factor

Open vs Closed

• Refers to whether the vaginal tunic is incised.
• Personal preference.
• A more complete removal of vaginal tunic can be completed with the closed technique.

Hemostasis

• Just emasculators on spermatic cord are indicated for routine castrations on young horses.
• Emasculate cremaster and spermatic cord separately for castrations on larger, mature stallions.
• Ligatures on spermatic cord: Circumferential, Transfixation, Miller's, Modified Miller's, or Roeder's Knot are all appropriate, with clinician preference.
• Ligation involves a pre-tied loop.
• Completed using a circumferential or transfixation suture using 1 USP absorbable suture like Polyglyconate or Polygalactin 910 on spermatic cord
• Significantly reduces the incidence of omental herniation and evisceration; should be considered in those with increased risk of significant post-op complications.
• Ligation does not completely eliminate the risk, there is a 7.6% incidence of herniation in draft colts

Key Surgical Steps

• "Closed" castration technique is not really closed unless a ligature is used
• Goals: Remove all testicular tissue, complete hemostasis, no evisceration or herniation, and effective drainage.
• Aclomplished by many different techniques

Emasculators

• "Nut to Nut": Surgeon should always check the nuts before cutting
• Crushing tool for hemostasis.
• Styles vary by clinician preference and region.
• Serra or Reimer style are most common.
• Method should provide means for cutting
• The Modified Whites is a noncutting version.
• The Reimer is a separate cutting emasculator.
• The Serra is a combined cutting emasculator.

Drainage

• Effective drainage methods include making long incisions, stretching incisions, connecting the two incisions and remove the ventral scrotum, or Excising the median raphe

Anesthetized Closed Castration

• Use a scrotal approach
• Post op keep incisions open

Scrotal Ablation

• Involves castration with removal of scrotal skin and primary closure.
• Procedure avoids many post-operative complications.
• More time consuming and costly.
• May be more popular in affluent areas.

Aftercare

• Exercise is needed to keep incisions open and minimize edema formation.
• NSAIDs (3-5 days)
• Monitor for bleeding and tissue protrusion.
• Castration incisions are typically left open to heal by second intention.
• Postoperative edema is likely.
• Encourage exercise.
• Forced exercise by riding or hand walking for 30 minutes daily is key.
• Orally administer two grams of Phenylbutazone once daily for 3 days to help minimize edema and discomfort.
• Signs that this has occurred include; lameness, reluctance to move, scrotal edema, horse does not clean up feed, or the rectal temperature is greater than 101.5° F. If any of these signs are observed, please call.

Complications

• Scrotal and preputial edema
• Hemorrhage
• Omental herniation
• Seroma
• Evisceration
• Others: fever, lameness, colic, septic peritonitis, tetanus, and penile damage.
• All can be prevented or minimized by good surgical technique and aftercare.

Hemorrhage

• Hemorrhage is often from transected cutaneous vessels that converge on the inguinal canal.
• Monitoring: ok to monitor if you can count the drips.
• Treatement: Ligate drips you cannot count and act quickly if it is a stream of blood.
• Keep horse quiet.
• Attempt to find bleeding vessel standing.
• Pack scrotum with gauze.
• Anesthetize and ligate bleeding vessel
• Consider Intravenous formalin (though controversial)

Omental herniation

• This should be promptly addressed, and may need to occur during ER hours (not a 5 alarm emergency).
• Keep the horse confined and calm/still.
• Clean the area, ligate, and excise (may do standing or may need anesthesia).

Post-op Seroma

• Has sealed incisions
• Open incisions to allow drainage

Evisceration

• Treatment: Referral strongly advised/essential!
• All-hands-on deck emergency.
• Important to remain calm and think.
• Keep horse calm & still.
• Protect the bowel & keep it moist & clean with clean towels to support.
• Anesthetize and place in dorsal recumbency.
• Make an inguinal approach over the external inguinal ring.
• Locate the vaginal tunic.
• Lavage and replace bowel through the deep inguinal ring into abdomen.
• Pack inguinal canal with gauze and begin broad spectrum antimicrobial therapy.

Scirrhous Cord

• Sciirhous Cord: Aka septic funiculitis with an infected spermatic cord
• Results in chronic draining tract in scrotum
• Cause: Poor technique and contamination, especially during ligation.
• Surgical resection of affected tissue is required.

"Proud Cut"

• Layman's term for stallion like behavior following castration.
• Formerly was due to leaving a portion of the epididymis.
• Could be the result of the opposite- excising only the epididymis
• This is a differential diagnosis
• Cryptorchid
• Learned behavior: Should reduce until 60 days post-op
• ~ 20-30% of geldings will still exhibit sexual behavior, with ~ 5% may be aggressive, stallion-like.

Standing Castration

• Must select a clean quite site
• Free of obstructions
• Tranquilization
• Twitch restraint
• Local Anesthesia:
  • Must block scrotal incision, testicle, and spermatic cord
  • Incise from cranial to caudal pole of testes
  • Dissect the spermatic cord from the surrounding fascia using a gauze 4x4
• Use emasculators to crush and cut the spermatic cord
• Afterwards clean surgical equipment.

Cryptorchidism

• Will be covered in the male reproductive surgery chapter