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Orchitis and Epididymitis in Dogs and Cats


Autumn P. Davidson

, DVM, MS, DACVIM, Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis

Reviewed/Revised Jul 2020 | Modified Oct 2022
Topic Resources

Acute inflammation of the testis and/or epididymis is most commonly infectious (bacterial, fungal or viral). The source of infection can be hematogenous or urologic or by direct inoculation. Clinical signs include pain and enlargement of the testis or epididymis. Scrotal edema and excoriation of the scrotal skin may also be present. Orchitis and epididymitis are rare in cats unless due to trauma (bite wounds).

Orchitis and Epididymitis

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 identify and further evaluate the affected structures with direct diagnostic tests (eg, fine-needle aspiration) and to rule out differentials such as testicular torsion (color flow doppler), incarcerated scrotal herniation, hematoma, ora neoplastic mass. Abscessation can also be identified. The ischemic damage secondary to testicular torsion or incarcerated inguinal herniation becomes irreversible within hours.

Diagnostic tests in the dog should always first include evaluation for Brucella canis Brucellosis in Dogs infection. Cytologic examination of semen with bacterial and mycoplasmal culture are helpful, but semen collection from animals that are ill or in pain may be difficult, and contamination from normal urethral flora is inevitable. Testicular or epididymal specimens for cytology and culture are best obtained by ultrasound-guided 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 biopsy is rarely done. If future reproduction is not of importance, specimens can easily be obtained during castration; scrotal ablation may be indicated.

Even with identification of a causative infectious organism and appropriate antimicrobial treatment, the prognosis for maintaining fertility in infectious orchitis/epididymitis cases is guarded because of the potential for irreversible damage to the germinal epithelium, tubular degeneration, development of immune-mediated orchitis (secondary to breakdown of the blood-testis barrier), and obstruction of the duct system. These sequelae may take months to occur.

In the case of unilateral involvement, the unaffected testis/epididymis must be protected from damage by heat, swelling, 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 weeks. There is no completely successful treatment for B canis infection; castration is advised. All antifungal agents interfere with spermatogenesis, either directly or indirectly. The potential for involvement of the prostate by direct extension dictates the use of antibiotics with good prostatic penetration once inflammation has subsided (fluoroquinolones).

Alternatively, clients may interpret epididymal prominence as a mass when testicular atrophy is marked. These cases usually present with a history of semen abnormalities and subfertility, especially if bilateral. Histopathology of the testis may suggest a nonseptic, primary immune-mediated process (eg, lymphocytic-plasmacytic infiltration). Treatment with immunosuppressive drugs has been attempted without success because spermatogenesis is also arrested. As a result of inhibitory effects on the hypothalamic-pituitary-gonadal axis, glucocorticoids can cause testicular atrophy and infertility. Other noninflammatory causes of testicular atrophy include previous exposure to excessive heat, cold, cytotoxic agents, and hormonal causes (eg, glucocorticoids, estrogen from Sertoli cell tumor, iatrogenic exposure to human transdermal hormone replacement therapy). Chronic brucellosis can cause lymphoplasmacytic inflammation as well.

When maintaining fertility is not important, castration is the treatment of choice for orchitis and epididymitis. Lesions of the scrotal skin are treated the same as other skin lesions, keeping in mind that resection of scrotal skin can permit thermal damage to the testes by bringing them closer to the abdominal wall.

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