Diagnostic Approach to Equine Testicular Disorders

Abstract

Management of breeding stallions is crucial to equine reproduction. The longevity of the breeding career is the ultimate objective, whether the stallion is used for natural cover or for semen collection and artificial insemination. Stud farm veterinarians should be aware of the techniques used to evaluate testicular function and the diagnostic approach to testicular disorders in cases of emergency. This paper presents the clinical methods used to evaluate testicular health, including palpation, ultrasonography, biopsy, and fine-needle aspiration. The discussion of testicular disorders is broken down into four categories: congenital disorders (cryptorchidism, monorchidism, and testicular hypoplasia), differential diagnosis of scrotal enlargement, differential diagnosis of causes of progressive testicular enlargement, and differential diagnosis of testicular asymmetry or reduction in size with an emphasis on testicular degeneration. The sudden increase in testicular size is often accompanied by severe clinical signs and is a major cause for referral of stallion for surgery. Testicular disorders are illustrated with clinical cases seen by the authors.

Keywords: biopsy; cryptorchidism; degeneration; hernia; orchitis; scrotum; stallions; testis; trauma; ultrasonography.

Figure 1

Measurement of the total scrotal width in a stallion using calipers.

Figure 2

Testicular measurements using calipers technique. (a) Length, (b) width, (c) height.

Figure 3

Testicular measurements by ultrasonography (a,b) length, (c,d) width, (e,f) height. Note the homogeneous appearance of testicular parenchyma. Arrows indicate the central vein (mediastinum testis).

Figure 4

Normal testicular ultrasonography. (a) spermatic cord (t.a. testicular artery), (b) head of the epididymis (h.e), (c) testis, (d) tail of the epididymis (t.e).

Figure 5

Testicular biopsy technique in stallions using a self-firing Bard Biopty instrument. (a) administration of lidocaine at the biopsy site, (b) incision of the scrotal skin and vaginal tunic, (c) insertion and firing of the biopsy instrument.

Figure 6

Testicular histology from a 5-year-old Friesian stallion with spermatogenic arrest and reciprocal translocation rcp (13; Y) (pter; qter).

Figure 7

Congenital inguinal hernia in an 2-day-old Arabian foal.

Figure 8

Congenital inguinal hernia in a thoroughbred foal managed by manual reduction and placement of truss.

Figure 9

Transcutaneous ultrasound imaging zones to determine the location of a cryptorchid testis: inguinal imaging (red), caudo-cranial transabdominal imaging (blue).

Figure 10

Transcutaneous inguinal ultrasonography. (a) Partial abdominal, and (b) complete abdominal cryptorchid testes.

Figure 11

Transcutaneous transabdominal ultrasonography of a complete abdominal testis.

Figure 12

Transrectal ultrasonography of abdominal testis. g: Gubernaculum, ub: urinary bladder, t: testis, pp: pampiniform plexus.

Figure 13

Appearance of the scrotum of stallion that sustained a testicular trauma (a kick) to the left testis during breeding.

Figure 14

Ultrasonogram showing scrotal edema (arrow) following a traumatic injury. t: testis, ce: cauda (tail of) epididymis.

Figure 15

Testicular rupture and hemorrhage. (a) ultrasonographic image showing the irregular contour of the testis due to rupture albuginea, (b) ruptured testis (arrow) during the unilateral castration. (t: testis).

Figure 16

External appearance of the scrotum in 2 stallions. (a) Indirect Inguinal hernia of the jejunum in an Andalusian stallion, (b) inguinal hernia of the large intestine in a quarter horse stallion.

Figure 17

Ultrasonographic images of inguinal hernia of the omentum (top) and jejunum (bottom). T: testis, o: omentum, i: intestine).

Figure 18

Right 180-degree spermatic cord torsion in a stallion. Note the cranial location of the tail of the epididymis (arrow).

Figure 19

Ultrasonography of the spermatic cords (top) and the testes (bottom) in a stallion with a unilateral spermatic cord torsion. T: testis.

Figure 20

Ultrasonographic (top) and gross (bottom) of orchitis with abscessation of the testis due to Corynebacterium pseudotuberculosis in a stallion.

Figure 21

Ultrasonographic appearance of epididymitis in a stallion.

Figure 22

Gross (top) and ultrasonographic appearance of hydrocele in stallions in an environment of high heat index. (a) Moderate, (b) severe, (c) spermatic cord, (d) testis.

Figure 23

Ultrasonographic appearance of a pyocele (arrows) in a stallion with post-surgical peritonitis.

Figure 24

Ultrasonographic appearance of varicocele in a stallion.

Figure 25

Gross appearance of testicular seminoma in a stallion.

Figure 26

Ultrasonographic appearance of seminoma in a stallion.

Figure 27

Histological features of testicular seminoma from a stallion.

Figure 28

Gross appearance and fine needle aspirate from cutaneous scrotal lymphosarcoma (nodules indicated by arrows) in a Quarter horse stallion.

Figure 29

Premature round germ cells seen in ejaculate from a stallion with testicular degeneration.

Figure 30

Histological features of severe testicular degeneration in a stallion.