10 Equine Male Reproductive Surgery

Equine Male Reproductive Surgery

• The presentation covers equine male reproductive surgery, addressing the diagnosis and management of conditions such as cryptorchidism and penile/preputial trauma.
• Dylan Lutter DVM, MS, DACVS-LA from Kansas State University delivers the information.

Objectives

• Diagnose cryptorchidism in horses.
• Understand the anatomy of the external genitalia.
• Learn how to manage penis and preputial trauma.
• Discern differential diagnoses for granulomatous lesions.
• Know surgical and medical options for genital neoplasia and their limitations.
• Understand the indications and basic techniques for reefing, phallectomy, and en bloc resection.

Overview

• Topics include cryptorchidism (testicular descent, diagnosis, surgical procedures), anatomy of the equine penis & prepuce, equine penile & preputial disorders (wounds/trauma, paraphimosis/priapism, intersex patients, granulomatous lesions, hematuria/hemospermia), and surgical procedures for the equine penis & prepuce.

Cryptorchidism

• Cryptorchidism is also known as "crypt," "Rig," or "Ridgling."

Inguinal Canal

• The external inguinal ring is a slit in the EAO directed Craniolaterally.
• The internal inguinal ring is directed dorsolaterally.
• Cranial border: caudal edge of IAO
• Ventromedial border: rectus abdominus/prepubic tendon
• Caudal border: Inguinal ligament
• External pudendal vessels & genitofemoral nerve pass caudally.
• Spermatic cord/testicle passes cranially.

Testicular Descent

• Mediated by androgens.
• Gonads in the fetus originate near the caudal pole of the kidney and become testes (or ovaries) at 40 days gestation.
• The gubernaculum extends from the caudal pole of the testes through the inguinal canal.
• By day 45 of gestation, the peritoneum invades through the canal, forming the vaginal cavity.
• At 5 months of gestation, the epididymis descends into the vaginal process.
• At 8.5 months gestation, the vaginal ring enlarges, and the gubernaculum starts to shorten, pulling the testes into the inguinal canal.
• Between 270 and 300 days of gestation the testicles remain there until birth.
• Within the first few weeks of neonatal life, the vaginal ring shrinks in size to approximately 1 cm in diameter, preventing things from going in or out.
• The deep inguinal ring atrophies in the early weeks after birth, trapping the testicle on whichever side of the deep ring it is on.
• HCG has been used to stimulate descent in people and has been described in horses, but is not routinely done due to limited knowledge.

Cryptorchid Definitions and Facts

• AQHA definition: Less than two visible testicles descended into the scrotum, and is also a genetic defect.
• AAEP definition: Any animal that does not have two testicles palpable in their entirety below the external inguinal rings.
• Causes persistent stallion-like behavior.
• Affected horses may develop neoplasia.
• Can be definitively diagnosed by 2 months of age.
• Failure of descent of the testicle occurs at a 10-15% incidence.
• Improper development causes infertility.
• 10% of crypts are bilateral.
• Inguinal crypts: Caught in inguinal canal, “high flanker”, and more commonly on the right (56% of right-sided crypts).
• Abdominal crypts: Caught in the abdomen, most common, more common on the left side (75% of left-sided crypts), usually near the vaginal ring and may be near the kidney.

Ethics of Cryptorchidism

• Performing surgical or other procedures to conceal genetic defects in animals to be shown, bred, raced, or sold as breeding animals is unethical, aligning with AAEP ethical and professional guidelines.

Diagnosis of Cryptorchidism

• Requires a history, physical exam, rectal palpation, ultrasound and hormonal testing.
• Note that history is often unavailable or unreliable.
• Physical exam involves examination for incisional scars and palpation of superficial inguinal rings.
• Hormonal testing with HCG stimulation test is the gold standard, anti-Mullerian Hormone, basal testosterone, and unconjugated estrogens are also helpful but less predictable.

HCG Stimulation Test

• Administer 5,000-10,000 units of HCG intramuscularly (IM) or intravenously (IV).
• Perform Testosterone assay.
• Time 0.
• 1 hour.
• 6 hours & 12 hours.
• 24 hours
• Results of greater than 100 pg/ml indicate cryptorchidism.
• Results of less than 40 pg/ml indicate geld.
• You should be looking for a 200% increase over baseline at 1 hour.

Cryptorchid Surgery: Laparoscopic vs. Open

• Laparoscopic Cryptorchidectomy: Can be done standing, has a lower complication rate, shorter lay-up period (7-10 days), requires specialized equipment that may be more costly, and has a very steep learning curve.
• Open Cryptorchidectomy: Is a well-established approach that has been described for over 100 years, does not require special equipment, is fast with experience, has a very steep learning curve, may retrieve an abdominal testicle without hand entering the abdomen, has a higher risk of post-op complications (hernia, evisceration), and has a longer lay-up period including stall rest for several days and restricted activity for 3-4 weeks.

Open Surgical Cryptorchidectomy Approaches

• Inguinal Approach: Most useful for inguinally retained testicles, often palpable, involves the surgeon reaching through the inguinal ring, and requires closing the external ring to prevent evisceration.
• Parainguinal: It involves a parallel incision just cranial & medial to the inguinal ring, often as a backup plan if determined to be an abdominal testes, and does not disrupt the vaginal tunic.
• Suprapubic, Paramedian: 10 cm lateral to midline at level of the prepuce.
• Flank: Requires paralumbar fossa incision large enough for surgeon's arm.

Key Steps for Inguinal Approach

• Incise directly over & parallel to the palpable inguinal ring.
• Blunt dissection down to the ring.
• Grasp the gubernaculum.
• Apply traction to expose the vaginal process.
• Incise the vaginal process to expose the epididymis.
• Continue traction on the epididymis until the testicle is exposed.
• Enlargement of the deep inguinal ring may be necessary.

Standing Laparoscopic Cryptorchidectomy

• It’s pre-op preparation is similar to standing laparoscopic ovariectomy.
• Plan for standing chemical restraint.
• The horse must be well-behaved enough to stand in stocks.
• Cryptorchids are often poorly trained and half wild.
• Surgeons may prefer a reduced bulk diet before surgery to increase intra-abdominal visualization.
• Anesthetized laparascopic cryptorchidectomy is also an option.
• May need to convert to an open approach if visualization is poor.

Male Reproductive System: Components of the Equine Penis

• Root of the penis: Composed of 2 crura (R & L portions of the CCP) that converge & form the shaft of the penis.
• Shaft of the penis: Major portion that contains 2 erectile bodies called the corpus cavernosum penis (CCP) and corpus spongiosum penis (CSP).
• Glans: Terminal portion and enlargement of CSP with 3 parts and a urethral process.

External Anatomy of Equine Prepuce

• Commonly called the "sheath."
• Folded sleeve of the skin that covers the free portion of the penis.
• Contains 2 layers, aka laminae: External (haired) and Internal (hairless).
• Has 2 cavities separated by the preputial fold: Internal & external.
• Also contains a preputial ring.
• In foals, the epithelium of the internal lamina is fused with the penile epithelium and a cytolytic process, controlled by androgens, forms the 2 laminae by 1 month old.

Erectile Tissues of the Penis

• Corpus Cavernosum Penis: Major erectile tissue covered by Tunica Albuginea which sends in fibrous trabeculae to for a cavernous framework in the CCP.
• Corpus Spongiosum Penis: Proximal unlargement is the Bulb of the Penis that surrounds the urethra and enlarges at termination to form the glans penis.

Clinical Examinations

• Urination- put in a freshly bedded stall to observe and catch urine.
• Erection/Ejactulation.
• Palpate preputial cavities, and urethral sinus, externally inguinal rings, and rectally palpate sex glands, root of penis, inguinal rings
• Visual inspection, sedation, manual traction.
• Block the pudendal nerve if necessary.
• Options are ultrasonography, endoscopy, cytologic fluid exam.

Intersex/Pseudo-hermaphrodite

• Cosmetic surgery is sometimes performed.
• Should castration or spay be performed.
• Need to locate the gonads to determine the approach.

Wounds and Lacerations of the Penis

• Usually superficial, caused by kicks, jumping fences, or falls.
• Hematomas usually from superficial vasculature & not CCP/CSP.
• A "fractured penis" implies a ruptured CCP, which is rare.
• For lacerations, debride & suture open wounds, ensure hemostasis, control infection, consider urethral involvement for patency, and potentially place a stent/indwelling urethral catheter.
• Partial amputation may be needed if there is severe trauma.
• For hematomas, compression is used to control hemorrhage & reduce edema.
• Hydrotherapy & confinement are helpful.
• If persistent, investigate cause for more severe damage.

Mechanism of Erection

• Innervated parasympathetically from the pudendal nerve.
• Blood supply primarily from the internal pudendal: 3 br.- bulb, deep, dorsal arteries of the penis.
• External pudendal contributes branches to the dorsal artery.
• Obturator contributes to the deep artery.
• CCP parasympathetic outflow dilates & straightens coiled branches of the deep artery of the penis, filling he cavernous spaces of CCP and venous outflow from CCP is obstructed by ischiocavernosus muscle contraction i.e. closed system.
• CSP artery enters at the bulb of the penis and remains an open system during erection, and outflow is from the dorsal veins of the penis.
• The dorsal artery of the penis courses over the dorsal border and supplies the free end (glans).

Phimosis

• Phimosis is the inability to extend the penis, caused by trauma- edema or scar tissue.

Paraphimosis

• Paraphimosis, is the inability to retract the penis with prolonged sedation/nerve block, very low but inherent risk with phenothiazine tranquilizer use, ~1 in 10,000 horses, stallions, paralysis, neoplasia, and severe debilitation.
• Paraphimosis is edema- accumulation of excess interstitial fluid due to alteration of Starling's forces (Increased capillary permeability and increased hydrostatic pressure.)
• Goal is to replace penis back into prepuce with hydrotherapy, NSAIDs, topical sweat, Sling, Probang if needed, and purse string suture in preputial orifice.

Paraphimosis/Penis Trauma

• Apply an Esmarch bandage, secure the penis in the prepuce with a purse-string suture for 10-14 days.
• If paraphimosis persists, phallectomy is indicated.

Priapism:

• Persistent erection with an unknown mechanism.
  • High-flow: increased arterial flow, rarely reported-true incidence unknown.
  • Low-flow: results in stasis of blood in CCP to form clot, more common.
• Treatment for acute conditions (within a few hours) includes 8 mg Benztropine, slowly IV, most effective if acute (anticholinergic effects), 62- agonists reported in men Clenbuterol suggested but untested in stallions, 10 mg Phenylephrine (a-1 agonist) QS to 10ml saline directly injected, and q 15 min reported in men, unknown in hores.
• Treatment for chronic or non-responsive cases includes irrigation of CCP with 10 IU heparin/ml saline through large bore needles from glans to 10 cm caudal to scrotum with phenylephrine injection at the end of lavage.
• CSP/CCP shunt -perineal region Suture 3 cm opening in the tunica albuguinia between CSP & CCP.

Granulomatous Lesions Differentials

• Relevant for anywhere on the body.
• Not just the penis.
• All are common in this area.
• Include sarcoid, squamous cell carcinoma, habronemiasis, granulation tissue, phycomycosis (pythiosis).
• Further differentiated by anatomic location, geography, and season.
• Sarcoid are most common skin tumor in horse.
• SCC- mucocutaneous junctions.
• Habronemiasis – summer months.
• Phycomycosis – gulf coast states.

Squamous Cell Carcinoma Diagnosis & Treatment

• Diagnosis is confirmed via Appearance, FNA / cytology, Impression smear / cytology or Excisional biopsy.
• Additional treatment methods include 5- fluorouracil or cisplatin intralesionally or as a topical cream (effudex), Cisplatin Electrochemotherapy, Beta- irradiation, and surgical excision.

Cryosurgery

• Freezing temperatures are used to cause cryonecrosis.
• Technique uses Liquid nitrogen -196 °C, with fast freeze - slow thaw, and a double cycle of 30 ° C.
• Debulking increases effectiveness of this treatment.

Urethral Tear

• Presented for Hemorrhage from penis in Stallions/ geldings.
• Located at the ischial arch.
• Identify with Endoscopy with difficulty visualizing.
• Needs surgical decompression & be prepared for hemorrhage in stallions.

Male Equine Surgeries include

• Segmental Posthetomy; Reefing
• Partial Phallectomy
• Phallopexy
• Perineal Urethrotomy/Urethrostomy