Pathology of the male reproductive tract

Question 1

What is the structure and function of the scrotum and its contents (testes, epididymis, vaginal tunics and espermatic cord)?

Answer 1

Produce spermatozoa and hormones, especially testosterone

Question 2

What is the structure and function of the accessory glands of the male repro tract?

Answer 2

Produce ejaculatory fluid to support, nourish, and protect spermatozoa

Question 3

What is the structure and function of the penis and prepuce?

Answer 3

Enter the vagina of the female and deposit the ejaculate

Question 4

What are the portals of entry into the male reproductive tract?

Answer 4

• Direct penetration
• Ascending infection
• Hematogenous spread
• Peritoneal spread

Question 5

What are the defence mechanisms of the male repro tract?

Answer 5

• Vulnerability to injury high antigenicity of spermatozoa and the long and narrow duct system
• Isolation for protection and prevention epithelial barrier
• Pattern recognition molecules, soluble factors, continuous flushing, rapid recruitment of inflammatory cells
• Blood testis barrier spermatozoa as foreign to the body
• Reduced immune responsiveness in the testes immunotolerance

Question 6

How does the scrotum (and its contents) respond to injury?

Answer 6

o Germ cell degeneration, death, and depletion
o Sertoli cells: swelling and vacuolation
o Injury to Leydig cells: ceases production of testosterone, impacting on spermatogenesis (increasing apoptosis and by inhibiting maturation of spermatids)
o Testicular compensatory hypertrophy
o Epididymis: severe injury leads to spermiostasis and potential rupture

Question 7

How do the accessory glands respond to injury?

Answer 7

Injury not common. It can lead to reduced function usually, but fertility is maintained

Question 8

How does the penis and prepuce respond to injury?

Answer 8

Excessive swelling or fibrosis may lead to stenosis and prevent penis extrusion

Question 9

What conditions can occur in the scrotal skin?

Answer 9

Susceptible to the same conditions as normal skin
- Dermatitis
- vascular disurbances
- skin tumours
- testicular tumours

Question 10

What conditions can occur in the vaginal tunic?

Answer 10

Susceptible to the same conditions as the peritoneum
- Hydrocele and haematocele
- Disorders of growth
o Mesothelioma and carcinoid
- Inflammation
o Trauma or local infection
o Adhesion: fibrinous and fibrous (limit the movement of the testes and alter its ability to thermoregulate)

Question 11

What conditions can occur in the testes and epididymis?

Answer 11

Degeneration -> testicular degeneration and atrophy

Inflammation -> orchitis, epididymitis

Disorders of growth -> testicular neoplasia, interstitial cell tumours, seminoma germ cells, teratomas

Question 12

Explain testicular degeneration and atrophy

Answer 12

• Uni - (local event) or bilateral (systemic problem)
• In young animals, difficult to differentiate from hypoplasia morphologically
• Major causes include: fever; local inflammation; nutritional deficiencies; ischaemia; obstruction; radiation and therapeutic drugs (amphotericin B, gentamicin, and chemotherapy); hormonal imbalance and senility
• Grossly: reduced in size and firm, areas of mineralization may be present
• Microscopically: decreased numbers of germinal cells, vacuolated Sertoli cells, intratubular multinucleated spermatids, and interstitial fibrosis

Question 13

What is orchitis?

Answer 13

• Inflammatory condition
• Less common than (but usually associated to) epididymitis
• Primary orchitis usually caused by haematogenous infection (Ex.: Brucella species and Corynebacterium
• Anti-inflammatory environment
• Spermatic granulomas may form
• Lymphocytic non suppurative orchitis may be associated to infertile animals
• Intratubular (most likely ascending and associated to epididymitis)
• Interstitial (usually incidental)
• Necrotizing (Ex.: Brucella species, FIP, severe trauma, ischaemia)
• Granulomatous (Ex: Mycobacteria or fungal infections)

Question 14

What is epididymitis?

Answer 14

• Inflammatory condition
   Epididymal enlargement
   Important in rams and dogs, bur rare in other species
   Any inflammation has the potential to cause obstruction of spermatozoal flow and spermatic granuloma
   Usually unilateral and followed by periorchitis
   Acute
  • Gross: swollen and soft
  • Microscopically: bacteria and neutrophils in the lumen, oedema, fibrin exudation, necrosis, extravasation of spermatozoa
   Chronic
  • Gross: firm, spermatic granulomas
  • Microscopically: neutrophils and macrophages in the lumen, epithelial hyperplasia, lymphocytes and plasma cells in the interstitium
   It may cause testicular degeneration
   Fibrinous or fibrous adhesions between vaginal tunics

Question 15

Explain the 4 neoplasms that can arise in the testes

Answer 15

 Sustentacular (sertoli) cell tumours
 Interstitial (leydig) cell tumours
 Seminoma germ cells
 Teratomas

Question 16

Explain Sustentacular (sertoli) cell tumours

Answer 16

More common in dogs, occasionally in bulls and stallions
• Approximately 25% of dogs with Sertoli cell tumours display signs of feminisation (hyperestrogenism)
o Bilateral alopecia, cutaneous hyperpigmentation, atrophy of opposite testis, pendulous prepuce, gynecomastia, decreased libido, attraction of male dogs to affected animal
• Bone marrow suppression is possible
• Prostatic squamous metaplasia
• Enlargement or distortion of affected testis up to 15 cm in diameter
• Local invasion is rare and metastasis uncommon
• Atrophy of seminiferous tubules in both affected and opposite testes

Question 16

Explain Interstitial (leydig) cell tumours

Answer 16

More common in dogs and bulls and relatively rare in stallions
• Enlargement or distortion of affected testis is rare
• 1-2 cm diameter, well demarcated, soft yellow orange
• Haemorrhage, necrosis and cystic degeneration
• Metastases are very rare
• Histologically large polyhedral cells with finely vacuolated eosinophilic cytoplasm
• Associated with an increased incidence of tumours of the circumanal glands
• Associated with prostatic hyperplasia, aggressive behaviour and increased volume of ejaculate
• Approx 16% show hyperstrogenism

Question 16

Explain Seminoma germ cell tumours

Answer 16

• Greater frequency in undescended testes
• May become quite large (>5 cm)
• Cut surface bulges above the surrounding parenchyma
• White to pale grey to tan in colour
• Foci of haemorrhage and necrosis may be present
• Delicate fibrous septa divide the main mass into lobules
• Mitotic figures are prominent
• Seldom malignant

Question 17

Explain Teratomas

Answer 17

Rare
• Never reported in dogs
• Young stallions, undescended testes

Question 18

Why would atrophy or metaplasia occur in the prostate?

Answer 18

• Atrophy occurs in any condition in which there is cessation of androgen stimulation
• Squamous metaplasia occurs with chronic irritation or increased estrogen stimulation

Question 19

What is it called when the prostate is enlarged due to an inflammatory condition?

Answer 19

Prostatitis
o Can be an important disease in dogs usually bacterial (commonly normal flora of skin or lower urinary tract)
 Common in ageing entire dogs
o Clinically important when there is toxaemia or urinary obstruction
o Usually together with hyperplasia Acute: ascending bacteria from urethra
o Chronic: unresolved acute lesions
o Abscess formation and replacement with fibrous tissue
o Important site for persistence of Brucella

Question 20

What disorders of growth can occur in the prostate?

Answer 20

• Benign prostatic hyperplasia
• Prostatic neoplasia - adenocarcinoma

Question 21

Explain benign prostatic hyperplasia

Answer 21

 Common in ageing entire dogs
 Hormone related castration is therapeutic
 Usually relatively regular bilateral enlargement palpable rectally
 May be cystic
 Most are asymptomatic
 Clinical signs usually restricted to constipation but can involve stranguria and haematuria
 Increased prevalence of urogenital tract infection

Question 22

Explain prostatic neoplasia - adenocarcinoma

Answer 22

 Relatively uncommon in dogs and rare inother species
 It is unclear in dogs whether prostatic neoplasia is related to hormonal environment
 Metastasis to urinary bladder, iliac lymph nodes, pelvis and lungs
 Irregular enlarged prostate on rectal palpation

Question 23

What are some of the circulatory disturbances that occur in the penis and prepuce?

Answer 23

Haemorrhage and penile haematoma

Question 24

What inflammatory conditions can occur in the penis and prepuce?

Answer 24

Balanitis (glans penis)/posthitis (prepuce)/balanoposthitis (prepuce & glans penis) o Common in castrated animals  due to hormonal changes o Urination within the prepuce - overgrowth of bacteria o Preputial microbial flora - secondary to trauma o Other examples:  Herpesvirus (Bovine Herpesvirus 1, Canine herpesvirus, Equine herpesvirus 3  Ovine ulcerative posthitis (Corynebacterium renale)  Parasitic balanoposthitis (Habronema spp. in stallions , Strongyloides papillosus in bulls) o May result in phimosis (constriction of the orifice of the prepuce so that it cannot be drawn back over the glans)

Question 25

What disorders of growth can occur in the penis and prepuce?

Answer 25

- Transmissible venereal tumour -> dogs - Squamous cell carcinoma -> stallions and dogs - fibropapilloma -> bulls