Canine Reproduction - Common Questions

These notes form part of the Dogs NSW Member Education Breed Seminars, held on DOGS NSW grounds - Dr. Ciaran Galvin MVB (UCD IRELAND)

 

COMMON QUESTIONS WHICH YOU MAY OR MAY NOT KNOW THE ANSWERS TO?

My dog has only got one testicle. Why does this happen and what can I do?

Normal testicular descent occurs in three phases:

1. Abdominal translocation is downward migration and maintenance of the testis near the internal inguinal ring as the abdominal cavity elongates. The testis and epididymis on each side are attached to the gubernaculum, which mediates movement by growth and subsequent dehydration and shrinking of this gelatinous connective tissue. Physical presence of the testis is necessary at this stage, suggesting testicular weight, and secretion of testosterone and other secretory factors is important for this part of the process to occur.

2. Transinguinal migration is movement of the epididymis and testis through the abdominal wall, and is mediated by intra - abdominal pressure. Because the inguinal canal does not close until 6 months of age in dogs, on average, transinguinal migration of testes is possible until the said age and dogs should not be definitely diagnosed as cryptorchid until they are older than 6 months.

3. Inguinoscrotal migration is movement of the epididymis and testis into the scrotum. Testosterone is not necessary for this final stage, although it may play a role in the development of supportive structures guiding testicular movement.

Many factors play a role in testicular descent. Genetic factors most certainly play a role. In dogs, mode of heritability is undefined but testicular descent is most likely multi- genetic. The trait can be carried by bitches or dogs. Epigenetic factors (alterations in gene expression) and environmental factors also play a role. Retained testes are significantly more likely to become neoplastic than are descended testes. Because of this predisposition to neoplasia and the heritable component of pathogenesis, bilateral castration is strongly recommended. Cryptorchid dogs cannot be shown.

Compounds that have been reported to cause testicular descent in dogs include gonadotropin releasing hormone (50 to 750 μ g one to six times in dogs aged 2 to 4 months, success rate 26.6% of 301 dogs), and human chorionic gonadotropin (100 to 1000 I U intramuscularly four times in a 2- week period in dogs less than 16 weeks of age, success rate 84% of 25 dogs, or 300 to 1000 I U three to four times in dogs of an unspecified age, success rate 75%).
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No single compound has been demonstrated consistently to cause testicular descent in dogs. Artificially inducing testicular descent is an ethical concern.

Cryptorchidism

Cryptorchidism is a common condition in dogs, with a reported incidence of 1.2 to 6.8%. One or both testes may be retained; in unilateral cryptorchids, the right testis is the one most commonly retained. Testes are more commonly retained in the inguinal area than in the abdomen. Retained testes are usually small and atrophic, and are more likely to undergo neoplastic change when the dog is aged than are descended testes. The small size of retained testes makes them difficult to identify by palpation or diagnostic imaging. There are no reports of successful identification of non - neoplastic retained testes using radiography. Ultrasonography may be used, especially to confirm that a palpable inguinal mass is a retained testis and not a superficial inguinal lymph node. Although testicular tissue has a unique ultrasonographic appearance , abdominally retained testes are atrophic and may be difficult to identify unless torsion of the spermatic cord or neoplasia has caused testicular enlargement. Pathology of the testis may distort architecture of the tissue, causing a mixed echogenicity. Because location of retained testes is variable, ultrasonography is not commonly used to differentiate bilaterally cryptorchid dogs from castrated dogs.
Differentiation of bilaterally cryptorchid dogs with abdominally retained testes from castrated dogs may be achieved by (1) palpation of the prostate— the prostate atrophies within weeks of surgery in castrated males and shows normal age - related hypertrophy in males with testes; or by (2) elevated serum testosterone concentrations with challenge testing— administer 1 to 2 μ g/kg gonadotropin releasing hormone intramuscularly and draw blood for testosterone assay 60 minutes later. Any value greater than 3 n g/ml strongly suggests that at least one testis is present. Although it may be possible to identify retained testicular tissue using ultrasound, surgical exploration and castration must be recommended to remove that male from the breeding pool.

 

Are prostate problems common in dogs?

Prostate problems are very common in dogs over 6 years of age. The main issues affecting the prostate are benign prostatic hypertrophy and prostatitis.

BENIGN PROSTATIC HYPERTROPHY
Benign prostatic hypertrophy and hyperplasia (BPH) is an age- related phenomenon in male dogs and humans. Testosterone is metabolized to dihydrotestosterone, which is the active compound that stimulates increase in the glandular and connective tissue portions of the prostate. With increasing age, as testosterone secretion slows and relative estrogen secretion increases, prostatomegaly occurs even more quickly, such that the majority of dogs aged 5 to 6 years or more have significant BPH.

Clinical signs
Many dogs with BPH are asymptomatic. The classic clinical sign of BPH is dripping of bloody fluid from the prepuce unassociated with urination. Signs may worsen if the male dog is exposed to a bitch in heat. Other signs are referable to increased size and vascularity of the prostate and include hematuria (as bloody prostatic fluid drains into the urinary bladder), hemospermia, passage of ribbon - shaped stools, and rectal tenesmus. Systemic signs of disease are uncommon in the absence of secondary prostatitis.

Diagnosis
The prostate encircles the urethra at the neck of the urinary bladder. It is palpable per rectum until it becomes large enough to pull the bladder forward into the abdomen; eventually it may be palpable per abdomen. The prostate is symmetrical with a distinct median raphe. In dogs with BPH, the prostate remains symmetrical as it increases in size. The dog does not show evidence of pain when pressure is put on the prostate per rectum or when it contracts as the dog ejaculates. Rectal palpation is not a very accurate diagnostic procedure; in one study, BPH was not identified by rectal palpation in 44.8% of affected dogs. Ultrasonography reveals a uniformly enlarged prostate. Fine - needle aspirate may be performed with ultrasound guidance for collection of samples for cytology or culture. Ejaculated prostatic fluid also may be submitted for cytology and culture. In either instance, culture is used to rule out prostatitis.

Treatment
Castration is the best treatment for BPH because this is an androgen- mediated disorder and all significant androgen secretions arise from the testes. No medical therapy is as effective as castration for minimizing clinical signs of BPH. Significant reduction in prostate size occurs within 3 weeks of castration.

For valuable breeding dogs or others that cannot be castrated, several medical therapies are available. Treatment with estrogen compounds has been described historically but is not recommended. Therapy with progestins has also been described (megestrol acetate, 0.5mg/kg per os once daily for 4 to 8 weeks; medroxyprogesterone acetate, 3 to 4 mg/kg subcutaneously at intervals of 10 weeks or longer). Semen quality is not affected negatively by treatment with progestins.

The preferred medical therapy is with the human drug finasteride (Proscar ™ — 5 mg tablet; Propecia™ — 1mg tablet; dose regimen is 5mg once a day per os for dogs weighing 5 to 50 k g). Finasteride prevents conversion of testosterone to dihydrotestosterone, decreasing prostate size while retaining normal libido and spermatogenesis. No side effects have been reported with use of this drug in dogs. Semen volume decreases as prostate size decreases but conception rates and semen quality do not vary.

PROSTATITIS
Prostatitis is inflammation of the prostate gland. Causative bacterial organisms are those of the normal urethral flora. The normal canine prostate is built to withstand infection. Infection occurs secondary to prostatic or urinary tract disease. Benign prostatic hypertrophy is the most common underlying problem in intact dogs. Prostatic neoplasia, most commonly adenocarcinoma, is the most common underlying problem in castrated dogs.

Clinical signs
Acute prostatitis is associated with clinical signs typical of any acute infection. The dog may be febrile, lethargic, and in appetent. The dog may cry out when ejaculating or refuse to breed. Signs of benign prostatic hypertrophy (BPH) may also be present, including dripping of bloody fluid from the prepuce unassociated with urination, hemospermia, passing of ribbon - shaped stools, and rectal tenesmus. Dogs with prostatic adenocarcinoma usually have metastatic disease by the time prostate disease is evident. Signs may include cachexia, muscle atrophy, respiratory distress, lymphadenopathy, and ataxia. Chronic prostatitis is associated with fewer systemic signs. Generally, the clinical manifestation is as for the underlying problem. The dog may present for the complaint of infertility or poor semen quality.

Diagnosis
Diagnosis of prostatitis requires demonstration of growth of bacteria from the prostate. Prostatic fluid, collected by ejaculation or prostatic tissue, collected by fine - needle aspirate or biopsy may be submitted for culture and sensitivity. Rectal palpation may be used to determine prostate size and presence of pain upon palpation but is inaccurate for diagnosis; in one study, rectal palpation was used to identify prostatitis in only 23.6% of affected dogs. Ultrasound should be used to guide sample collection. On ultrasound, the infected prostate appears mottled and may have scattered mineralization. Prostatic neoplasia may appear more whorled in appearance. The two conditions cannot be definitively differentiated by ultrasound alone. There are no reported complications from fine - needle aspirate or biopsy of the potentially infected prostate. Diagnosis of the underlying disorder is best made by prostatic biopsy, especially if index of suspicion for prostatic neoplasia is high.

Treatment
In acute prostatitis, the prostatic capsule is disrupted and any antibiotic deemed suitable by culture and sensitivity will penetrate the prostatic tissue. In chronic prostatitis, the capsule is intact and only lipophilic antibiotics that are not highly protein bound are likely to penetrate the tissue well. Antibiotics most efficacious for treatment of chronic prostatitis include fluoroquinolones, trimethoprim- sulfa, and chloramphenicol. Long- term use of trimethoprim- sulfa drugs may be associated with anemia and keratoconjunctivitis sicca. Treatment with the antibiotic chosen should last for 4 to 6 weeks. Reculture prostatic tissue or fluid 1 week and again 1 month after therapy and retreat if necessary. Concurrent treatment for BPH with finasteride or castration may hasten resolution. If prostatic adenocarcinoma is present, the animal should be treated palliatively.

My dogs doodle will not go back in and he keeps licking it. What do I do?
Paraphimosis is extrusion of the non erect penis from the prepuce. Paraphimosis occurs most commonly in older, castrated toy breeds, although it may occur in any breed. Underlying causes are medical (balanoposthitis [infection of the penile and preputial mucosa], foreign object, neurologic disease) or behavioural. Erection of the penis is not hormonally mediated but is instead neurologic and so can occur in dogs regardless of intact status. Any irritation of the penile mucosa or of the nerves mediating erection and protrusion of the penis may cause drying of the penis and inability of the dog to retract the penis completely into the prepuce. Balanoposthitis is a secondary infection with the normal preputial flora. Underlying causes include foreign objects, prostate disease, and atopic dermatitis. Behavioral causes of paraphimosis include unintended positive reinforcement and sequencing. Many owners very vigorously scold the dog for extruding or licking at the penis; dogs may see this increased attention as a positive reinforcement. Similarly, dogs may learn a sequence of events (go out to urinate, lick at the penis, get a treat) and exhibit the behaviour for a reward.

Clinical signs
Paraphimosis is extrusion of the non - erect penis from the prepuce. This should be differentiated from priapism, which is persistent erection of the penis and which is associated with systemic effects and eventual nonviability of penile tissue. In dogs with paraphimosis, the exposed portion of the penis dries and reddens, especially if chronically exposed. The dog does not usually feel pain when the area is examined. If balanoposthitis is present, creamy, yellowish discharge overlies the penis when extruded and the penile and preputial mucosa is erythematous. Neurologic disease may be associated with other neurologic signs.

Diagnosis
Extrusion of the penis and inspection of the prepuce are diagnostic for balanoposthitis and presence of foreign objects. A sample of preputial discharge should be submitted for culture and sensitivity. Rectal examination of the prostate should be performed. In castrated dogs, the prostate should barely be palpable. Prostatomegaly in a castrated dog is highly suspicious of prostatic neoplasia, and carries a poor prognosis. The dog should be evaluated for atopic dermatitis. A complete neurological examination should be performed. Owners should be questioned about the frequency with which the problem occurs and about any possible sequencing leading to or reinforcing this behaviour.

Treatment
Balanoposthitis is treated with appropriate antibiotic therapy, based on culture and sensitivity, and treatment of the underlying cause, if identified. Behavioural causes should be addressed by teaching the owner not to overreact when disciplining the dog for the behaviour and to try to break up sequences leading to the behaviour. It may be beneficial to leave a leash on the dog when in the house so when he starts licking, the owner can just gently drag his head away from that area and distract him. If no cause can be identified, some dogs respond to therapy with progestins, which have anti- inflammatory and antianxiety properties. Examples include megestrol acetate (0.5 m g/kg per os once daily for a maximum of 30 days) and medroxyprogesterone acetate (2.5 m g/kg subcutaneously every 5 months with a maximum of two treatments). Side effects of progestins in male dogs are polyphagia, diabetes mellitus, and possibly mammary neoplasia. Some dogs self - traumatize to a large extent. These dogs may be best treated with antipsychotic drugs or tranquilizers. Surgical replacement and fixation of the penis has been described, with suturing of the dorsal penile epithelium to the apposing preputial surface.

Article appeared in DOGS NSW magazine, April 2018 edition.