Lecture 27- Stallion Infertility

What are the major causes of breeding injuries in stallions?

Kicks, mounting fences/walls, breeding hobbles, and phantom collection injuries

What body regions are commonly injured during breeding accidents?

Body, penis, and testicles

What penile injury may occur during phantom collection?

Rupture of the dorsal artery of the penis

What structures may be damaged during phantom collection injuries?

Glans penis and penile shaft

What normal penile finding is commonly mistaken for pathology?

Dorsal venous plexus

How does the normal dorsal venous plexus appear?

Non-uniform swelling on the dorsal penile surface

What are the major categories of testicular degeneration?

Unilateral or bilateral; temporary or permanent

What is a common cause of testicular degeneration?

Thermal injury

What environmental factors may cause testicular degeneration?

Increased ambient temperature and scrotal insulation

What forms of scrotal insulation can impair thermoregulation?

Edema, dermatitis, and hemorrhage

What conformational problem may contribute to testicular degeneration?

Incompetent testicular heat-exchange system

What additional causes of testicular degeneration were mentioned?

Age, parasite migration, blood flow abnormalities, and vasculitis

What is the most common cause of testicular degeneration in stallions?

Age-related degeneration

What lesions are associated with age-related testicular degeneration?

Gradually developing vascular lesions

What cellular change occurs early in age-related testicular degeneration?

Altered Sertoli cell function

What endocrine abnormality may accompany age-related degeneration?

Pituitary dysfunction and hormonal imbalance

What semen abnormalities are characteristic of testicular degeneration?

Low sperm concentration and high numbers of primary morphological defects

What endocrine tests may aid diagnosis of testicular degeneration?

GnRH challenge, hCG stimulation, and hormone assays

What hormone concentrations are commonly measured during testicular degeneration workup?

Testosterone, estrogen, FSH, LH, and inhibin

What hormonal pattern is associated with testicular degeneration?

Increased FSH; decreased inhibin and estrogen; normal LH and testosterone

How can testicular degeneration be differentiated from testicular hypoplasia?

Degeneration requires previously normal size, texture, and function

What are the characteristics of mild testicular degeneration?

Normal/slightly small testes with slightly soft to soft consistency

What are the characteristics of severe testicular degeneration?

Marked reduction in testicular size and firm consistency

What histologic change occurs in severe testicular degeneration?

Connective tissue replaces normal testicular parenchyma

What palpation finding develops as testes decrease in size?

Wrinkled tunica albuginea

What epididymal finding may occur with advanced degeneration?

Epididymides feel disproportionately large relative to testes

How does testicular torsion typically present?

Painful, acute onset scrotal enlargement

What important clinical reminder was emphasized regarding stallions presenting for colic?

Always examine the testicles

Which breed is most commonly affected by testicular torsion?

Standardbreds

What physical examination finding is common with testicular torsion?

Enlarged swollen testicle

How is testicular torsion diagnosed?

Epididymal-tail orientation and ultrasonography

Does testicular torsion tend to recur?

Yes

What treatment is recommended when a torsed testicle is compromised?

Unilateral or bilateral orchiectomy

Can an abdominal retained testicle undergo torsion?

Yes, causing severe abdominal pain

What structures should be palpated to determine testicular orientation?

Epididymal tail and ligament of the tail of the epididymis

What is the normal texture of the epididymis?

Soft and spongy

Can a testis be rotated 180° without clinical signs?

Yes

Can some stallions experience intermittent spontaneous torsion?

Yes

How do spontaneously rotating testes behave?

Freely movable and easily returned to normal orientation

Do stallions with mild intermittent torsion necessarily show pain?

No

What is known about the effect of intermittent torsion on semen quality?

The effect is unknown

What are the major causes of orchitis?

Traumatic, infectious, parasitic, and autoimmune

How do infectious causes of orchitis usually reach the testis?

Hematogenous spread

Which infectious diseases were associated with orchitis?

Equine influenza, streptococcal infections, and Salmonella

Which parasite was specifically mentioned as a cause of orchitis?

Strongylus edentatus

What autoimmune mechanism can lead to orchitis?

Disruption of the blood-testis barrier

How is orchitis commonly treated?

Long-term antibiotics and NSAIDs

Why may acute orchitis require hemiorchidectomy or hemicastration?

Risk of damage to the opposite testis and poor recovery of the affected testis

Is primary bacterial epididymitis common in horses?

No, it is uncommon

What relationship exists between epididymitis and orchitis?

Epididymitis almost always accompanies orchitis

What organism causes most reported cases of epididymitis?

Streptococcus equi zooepidemicus

What may serve as the original nidus for epididymal infection?

Verminous migration

What clinical signs may be seen with epididymitis?

Lethargy, inappetence, abdominal pain, or no signs

What diagnostic samples may be collected for epididymitis?

Semen culture and fine-needle aspirates

What ultrasonographic finding is associated with epididymitis?

Dilated anechoic pockets

How well does epididymitis respond to antibacterial therapy?

Poorly

What is often the most practical treatment for epididymitis?

Unilateral orchidectomy/hemicastration

How do testicular neoplasms usually present?

Painless with insidious onset

What is the most common testicular tumor in older stallions?

Seminoma

What cell type gives rise to seminomas?

Germ cells

In which age group are seminomas generally diagnosed?

Sexually mature males

How do seminomas typically appear grossly?

Pale, soft, and lobulated

What is the most common testicular tumor in young stallions (<2 years)?

Teratoma

What cell type gives rise to teratomas?

Pluripotential stem cells

Which testicular tumor produces testosterone?

Interstitial (Leydig) cell tumor

Which testicular tumor produces estrogens?

Sertoli cell tumor

What is the overall prognosis for testicular neoplasia?

Generally good

How can testicular neoplasia affect fertility?

May interfere with thermoregulation

Where should tumor extension be evaluated in cases of testicular neoplasia?

Spermatic cord

What differential diagnoses should be considered with scrotal enlargement?

Testicular torsion, scrotal hernia, varicocele, hydrocele, epididymitis, orchitis, and periorchitis

What is a varicocele?

Dilation of the pampiniform plexus

What is the most common neoplasia of the equine penis/prepuce?

Squamous cell carcinoma (SCC)

In which equine population is SCC more common?

Geldings

How does penile SCC typically appear?

Plaques or shallow roughened ulcerated lesions

What treatment options exist for penile SCC?

Cryosurgery, surgical excision, reefing, penile amputation, and topical therapies

What is the second most common preputial tumor?

Sarcoid

What causes summer sores?

Habronema muscae larvae

Where are summer sores most commonly located?

Urethral process and preputial orifice

Is the scrotum a common site for summer sores?

No

What type of tissue reaction occurs with summer sores?

Granulomatous inflammation

What gross lesion is characteristic of summer sores?

Yellow caseous granules

How can summer sores interfere with normal function?

May obstruct urination

What is the primary treatment for summer sores?

Ivermectin

What concern exists regarding ivermectin therapy?

Possible resistance

What additional treatment may be required for summer sores?

Systemic and topical moxidectin

Define paraphimosis.

Inability to retract a flaccid penis into the prepuce

What are the key features of paraphimosis?

Penile prolapse, paralysis, and inability to retract

What conditions may precipitate paraphimosis?

Trauma, surgery, tranquilizers, exhaustion, and severe debilitation

What neurologic diseases may cause paraphimosis?

Herpesvirus infection, protozoal myelitis, rabies, and dourine

What is the most important immediate treatment for paraphimosis?

Support the penis

How does prognosis change with duration of paraphimosis?

Progressively worsens over time

What supportive therapies are recommended for paraphimosis?

Penile support, massage, hydrotherapy, and moderate exercise

How long should supportive therapy generally continue?

At least one month

When is improvement typically observed in paraphimosis?

Within 7-10 days

What complications develop if paraphimosis fails to respond?

Thrombosis, fibrosis, skin excoriation, cold insensitive penis

What salvage procedure may ultimately be required for severe paraphimosis?

Castration and penile amputation

What important surgical rule was emphasized before penile amputation?

Castration should be performed first

Define phimosis.

Inability to protrude the penis from the prepuce

What clinical sign is commonly observed with phimosis?

Urine dribbling

What congenital defect commonly causes phimosis?

Congenital stricture of the preputial ring