CASE 2: Azoospermia (lack of spermatozoa in the ejaculate) in a dog
Case Information:
In 8-year-old, intact male Vizsla was presented for the complaint of poor semen quality. The dog was a proven sire, with litters born 3.5 and 5 years prior to presentation. Brucellosis testing had been negative at the time of the last breeding. His most recent history is that he had had semen collected for freezing at another clinic five months earlier. Two semen samples were collected; the first contained few spermatozoa and the second contained no spermatozoa. The semen was cultured and Streptococcus sp. were identified; the dog was treated with an appropriate antibiotic to no effect.
Semen was collected again four months later. It again contained no spermatozoa. At that time, samples were collected for assessment of thyroid hormones, and bloodwork to assess general fitness; all tests were within normal limits.
On physical examination, the dog had small testes. Both were of normal consistency, but the surface of the right testis was irregular. The prostate was palpably normal on rectal examination.
Semen was collected and again no spermatozoa were present. The semen was cultured and no significant growth of bacteria occurred. Alkaline phosphatase, an enzyme secreted into semen from the epididymes, which surround the testes, was measured in the semen to determine if a complete ejaculate was obtained. The value was high, indicating that the azoospermic semen sample did contain fluid from the testes.
Question:
What diagnostic tests allow us to determine what is happening within the testes?
Answer:
Ultrasound of the testes and epididymes allows visualization of the testicular tissue and may pinpoint small abscesses, tumors, or other local abnormalities of the testis that are not palpable.
Testicular biopsy may be performed either by aspiration with a small diameter needle or by collection of a wedge of testicular tissue. Fine needle aspirate is less invasive and requires only sedation of the dog, but yields less information than does collection of a wedge biopsy, which is quite invasive and requires general anesthesia for the dog.
Case Outcome:
Testicular ultrasound was performed. No obvious testicular lesions were identified.
Azoospermia, lack of spermatozoa in the ejaculate, can be caused by abnormalities from within the testes, such as infection, neoplasia (cancer), and bilateral cryptorchidism (retention of both testes in the groin or abdomen). Causes from outside the testes include poor collection technique, pain or apprehension on the part of the male dog, hypothyroidism, treatment with drugs that decrease spermatogenesis, and blockage of the epididymal ducts preventing outflow from the testes.
The dog was neutered and the testes submitted for pathologic evaluation. The left testis contained a 2-3 mm diameter mass (interstitial cell tumor), and the right testis contained 2 small masses (interstitial cell tumor and seminoma).
In summary, diagnostic tests appropriate to perform on a dog with no spermatozoa in the ejaculate include:
Measurement of alkaline phosphatase in semen
Bacterial culture of semen
Measurement of thyroid hormones in blood
Tests for general fitness of the dog, including complete blood count and serum chemistry profile
Canine brucellosis serologic test
Testicular ultrasound
Testicular biopsy