Aetiology and assessment of epididymo-orchitis
Epididymo-orchitis most commonly occurs as a complication of a urethral infection caused by Chlamydia trachomatis or Neisseria gonorrhoeae in males1 who are sexually active, or a urinary tract infection caused by enteric gram-negative bacteria. Males who engage in insertive anal sex are at risk of infection with sexually acquired enteric pathogens in addition to other sexually transmissible pathogensLampejo, 2017Taylor, 2015. In a significant number of cases, no pathogen is identified.
Epididymo-orchitis can also occur secondary to a number of systemic bacterial infections (eg extrapulmonary tuberculosis, syphilis, brucellosis, melioidosis), viral infections (eg mumps) and noninfective conditions.
Epididymo-orchitis can also develop after urinary tract instrumentation.
Acute scrotal pain or inflammation can be a urological emergency. Exclude alternative diagnoses (eg Fournier gangrene, testicular torsion, testicular abscess)Taylor, 2015.
Differentiating the cause of infection (ie a sexually transmissible or urinary tract pathogen) depends on clinical judgement and patient history. If the diagnosis is uncertain, or urethral discharge is present, use the empirical regimen for epididymo-orchitis suspected to be caused by a sexually transmissible pathogen until the results of investigations are available.
To determine if the cause of epididymo-orchitis is a urinary pathogen, obtain a midstream urine sample for microscopy, culture and susceptibility testing. To test for sexually transmissible pathogens (eg C. trachomatis and N. gonorrhoeae), also collect a first-pass2 urine sample for nucleic acid amplification testing (NAAT) (eg polymerase chain reaction [PCR]) in males who are sexually active, or those with urethral discharge. A urethral swab for Gram stain, culture, and susceptibility testing of N. gonorrhoeae should also be obtained if urethral discharge is present.