Canine Orchitis and Epididymitis: Localization, Sampling, and Brucella Testing

Bottom line

Localize the lesion before labeling scrotal enlargement epididymo-orchitis. Assess perfusion and surgical differentials promptly in an acutely painful patient. Include Brucella canis testing in dogs with suspected orchitis or epididymitis. [1] Plan sampling and staff protection together rather than treating biosafety as a laboratory afterthought.

Scrotal versus testicular localization

Inspect skin separately and palpate the testis and epididymis; pain and edema can obscure localization. [1]

Record laterality, onset, wounds, reproductive history, cryptorchid history, prior antimicrobials, and concurrent urinary signs. These are workup prompts, not independent diagnostic criteria. If discharge is preputial rather than scrotal, use the separate canine balanoposthitis workup.

Ultrasound and the torsion differential

Use B-mode imaging to map both testes, epididymides, and associated fluid; add Doppler assessment of perfusion. Acute orchitis may produce heterogeneous hypoechoic regions or abscessation. Torsion may show absent perfusion, while incomplete torsion may retain reduced flow. [2]

Torsion and strangulated hernia are time-critical ischemic differentials. [1] Do not postpone surgical assessment simply to finish an infectious workup. Treat equivocal imaging as unresolved localization, not proof of uncomplicated infection.

Cytology, culture, and histology

Urethral flora confound semen culture; ultrasound-guided aspiration supports lesion cytology and culture with analgesia or sedation. [1]

Agree the sampling plan with the laboratory before collecting potentially infectious material.

Reserve testicular biopsy; epididymal biopsy risks granulomas. Lymphoplasmacytic inflammation occurs in chronic brucellosis and immune-mediated disease. [1]

Do not diagnose immune-mediated disease from that pattern alone.

Once microbiology and lesion findings are available, make a patient-specific antimicrobial decision. The amoxicillin-clavulanate stewardship reference provides prescribing context, not a default regimen for orchitis or Brucella infection.

Brucella testing: negative is not clearance

Use a B. canis-specific testing pathway agreed with the reference laboratory. APHA recommends serology for most suspected cases; recent exposure may require repeat sampling. Negative blood culture or PCR does not guarantee absence of infection. [3]

APHA's UK guidance describes SAT and iELISA used together and cautions that commercial tests differ; interpret results with exposure history and assay characteristics. [3] Do not transplant one laboratory's validation figures to another test or present an unspecified PCR as a universal rule-out.

Zoonotic precautions before sampling or surgery

Risk-assess semen collection, aspiration, castration, and handling contaminated reproductive fluids. Control sharps, splashes, and aerosols; select protective clothing, gloves, eye protection, and respiratory protection according to the procedure. APHA guidance also calls for safe waste handling and appropriate laboratory containment. [4]

Label submissions with suspected brucellosis so laboratory personnel can take precautions. Follow local animal-health reporting guidance and alert relevant public-health services to possible human infection. [5]

Frequently Asked Questions

Does scrotal edema prove orchitis?

No. Pain and edema can obscure palpation-based localization. [1]

Can Doppler exclude torsion if some flow remains?

Not from that finding alone: incomplete torsion may show reduced rather than absent perfusion. [2]

Is a positive semen culture sufficient?

No. Urethral flora confound semen culture; interpret lesion-directed samples separately. [1]

Does a negative blood culture exclude Brucella canis?

No. Infected dogs may have negative blood culture or PCR results; these do not guarantee absence of infection. [3]

Which Brucella serology should I request?

Discuss the laboratory's B. canis-specific assays and exposure timing. APHA's UK pathway uses SAT and iELISA in parallel. [3]

What changes before aspirating a suspect case?

Risk-assess infectious fluids, sharps, splashes, and aerosols; agree protective measures and laboratory containment before sampling. [4]