Structure and Function of the Male Canine Reproductive Tract

Structure and Function of the Male Canine Reproductive Tract

By: Dr. Bari Spielman

What Are the Common Diseases of the Canine Male Reproductive Tract?

  • In the puppy, the testicles are initially located within the abdominal cavity. Within several days of birth, they begin to move downward and outward through the inguinal canal in the groin. Within 6 to 8 weeks of age, they have moved into the scrotum. Failure of a testicle to move into the scrotum is called an undescended testicle, or cryptorchidism. The undescended testicle may lie in the groin just outside the abdominal wall or it may be retained within the abdomen. Because the temperature of an undescended testicle is higher than normal, it is infertile. Testicles retained in the abdomen also have a higher incidence of developing tumors later in life.

  • Testicular tumors, torsions (twisting upon itself) and orchitis (inflammation of the testis) may also occur. Epididymitis (inflammation of the epididymis) is the most common disorder of the epididymis.
    Testicular tumors may not cause any clinical signs until they are large enough to be noticed. Torsion and inflammation of the testicle cause pain, irritation, and infertility. Inflammation of the testes may occur with bacterial infections, viral infections, trauma, and immune diseases.

  • Benign prostatic hypertrophy (enlargement) is common in older unneutered male dogs. The prostate gland slowly enlarges as the dog ages due to the chronic influence of testosterone hormone. This enlargement does not occur in castrated dogs. Excessive enlargement of the prostate may lead to urinary and rectal blockage, resulting in clinical signs of straining to defecate, straining to urinate and painful urination.

  • Other disorders of the prostate include the formation of abscesses following infection of the gland, the development of sterile cysts, and the growth of tumors. Most prostatic tumors in the dogs are malignant carcinomas.

  • Several disorders of the prepuce are seen in the dog. Phimosis is the existence of an abnormally small opening in the prepuce, which prevents protrusion of the penis. Paraphimosis is the inability to withdraw the penis into the prepuce. Priapism is persistent erection of the penis that is not associated with sexual excitement. It usually develops following certain spinal cord injuries or urinary infections. Inflammation and infection of the prepuce may also develop in the dog. Tumors of the prepuce may also occur. A contagious tumor that is spread during breeding is the transmissible venereal tumor.

  • Trauma may occur to the scrotum, prepuce and urethra. Trauma to the pelvis may affect the prostate gland. Such trauma may include blunt injuries from automobile accidents, bite wounds, and falling on to sharp objects.

    What Types of Diagnostic Tests Are Used to Evaluate the Canine Male Reproductive Tract?

  • A thorough physical examination and complete history are imperative for the successful management of any reproductive disorder. Diagnostic tests are tailored to the individual patient.

  • A complete blood count, biochemical profile and urinalysis are important parts of any baseline workup. The urine is often cultured for bacteria. Infection, inflammation and other systemic disorders need to be considered and/or ruled out.

  • Radiographs (x-rays) of the abdominal structures may be of benefit in many cases. An ultrasound may be performed on the prostate and testicles. This may require referral of your dog to a specialist in veterinary internal medicine or reproductive medicine.

  • Aspirates for cytology (microscopic cellular evaluation) and/or biopsies (microscopic tissue evaluation) of any masses and tumors are important. Biopsies may also be performed on the prostate. Aspirates and biopsies are occasionally performed on the testicles to assess male dogs known to be infertile. If the testicle is surgically removed, then biopsy is always indicated.

  • Semen analysis is sometimes performed to evaluate cases of infertility. Collection of a semen sample can be accomplished by allowing the male to mount a bitch (female dog) in heat, through the use of a teaser bitch, or by hand stimulation. Collected semen is examined microscopically and cultured for bacteria.

  • Serologic testing for Brucellosis may be indicated. Brucellosis is caused by a bacterium that may infect the male reproductive tract.

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