THE MERCK VETERINARY MANUAL
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Orchitis and Epididymitis in Small Animals

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Acute inflammation of the testis or epididymis can be caused by trauma, infection (fungal, bacterial, or viral), or testicular torsion. Infection can be hematogenous or urologic in origin. Clinical signs are pain and swelling of the testes, epididymides, and/or scrotum. There may be wounds or other lesions in the scrotal skin. Orchitis and epididymitis are rare in cats unless due to trauma.

The scrotal contents should be carefully palpated to identify which structures are involved, including the epididymis and testis, but patient discomfort and edema can make palpation difficult. Ultrasonography (with sedation or analgesia as needed) is helpful to further evaluate the affected structures and to confirm the presence of testicular torsion and focal (eg, mass, abscess) lesions in the testis or epididymis. It can also identify less common causes of scrotal enlargement such as scrotal hernia or hematoma.

Diagnostic tests should always include evaluation for Brucella canis infection. (Also see Brucellosis in Dogs.) Cytologic examination of semen with bacterial and mycoplasmal culture are also helpful, but semen collection from animals that are ill or in pain may be difficult. Testicular or epididymal specimens for cytology and culture may be obtained by fine-needle aspiration. Testicular biopsy for histopathology and bacterial culture may be performed, if needed, after less invasive diagnostic tests have been completed. Because of the greater risk of granuloma formation, epididymal aspiration and biopsy are rarely done. If future reproduction is not of importance, specimens can easily be obtained during castration.

Treatment is difficult unless the underlying cause can be identified. The prognosis for maintaining fertility is guarded despite aggressive therapy because of the potential for irreversible damage to the germinal epithelium, tubular degeneration, development of immune-mediated orchitis, or obstruction of the duct system. These sequelae may take months to occur. Application of cool water packs may decrease testicular damage caused by local swelling and hyperthermia; care must be taken not to damage the scrotal skin. In the case of unilateral involvement, the unaffected testis/epididymis must be protected from damage by heat, pressure, and direct extension of the disease process. Hemicastration may be prudent. If bacterial cultures are positive, appropriate systemic antibiotics should be administered for 3–4 wk. There is no completely successful treatment for B canis infection. All antifungal agents interfere with spermatogenesis, either directly or indirectly. The potential for inolvement of the prostate by direct extension dictates the use of antibiotics with good prostatic penetration once inflammation has subsided (fluoroquinolones). Culture and sensitivities should refine therapy.

Histopathology may suggest an immune-mediated process (eg, lymphocytic-plasmacytic infiltration); treatment with immunosuppressive drugs has been attempted without success. Chronic B canis infection also causes lymphocytic-plasmacytic inflammation. Furthermore, as a result of inhibitory effects on the hypothalamic-pituitary-gonadal axis, glucocorticoids can cause testicular atrophy and infertility. The ischemic damage caused by testicular torsion becomes irreversible within hours. When maintaining fertility is not important, castration is the treatment of choice for orchitis and epididymitis due to any cause. Lesions of the scrotal skin are treated the same as other skin lesions, keeping in mind that resection of scrotal skin can promote thermal damage to the testes.

Chronic orchiepididymitis may develop as a sequela of the acute syndrome, or there may be no previous history of testicular inflammation. Possible causes include those of acute orchiepididymitis, immune-mediated orchitis and epididymitis, neoplasia, and spermatocele or granuloma formation. Most animals are asymptomatic except for infertility. Physical examination often reveals testicular atrophy. Tumors may be palpable. Palpation of the epididymis may reveal induration or enlargement, which may erroneously be interpreted as dramatic relative to the atrophic testis. Epididymal atrophy is uncommon. Ultrasonography can help identify the lesions.

Other noninflammatory causes of testicular atrophy include previous exposure to excessive pressure, heat, cold, and cytotoxic agents. Hormonal causes (eg, glucocorticoids, estrogen from contralateral Sertoli cell tumor, iatrogenic exposure to human transdermal hormone replacement therapy) are also possible.

The prognosis for return of normal fertility in cases of chronic orchitis/epididymitis is grave. If warranted by the dog's value as a stud, the diagnostic and therapeutic plan is as described above for the acute condition.

Last full review/revision October 2013 by Autumn P. Davidson, DVM, MS, DACVIM

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