Epididymitis Epididymiorchitis

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Epididymitis and Epididymo-Orchitis

Definition and Anatomy

The epididymis is a tightly coiled tubular structure along the posterior aspect of the testis where sperm mature before transiting to the vas deferens. Epididymitis is inflammation of this structure. When the adjacent testis is also involved - which happens in the majority of bacterial cases - the combined condition is termed epididymo-orchitis. It is the most common intrascrotal inflammatory disease, predominantly affecting men aged 18-35 years, though it can occur at any age.

Rosen's Emergency Medicine, p.1404
Schwartz's Principles of Surgery, p.1789

Pathophysiology

Infection reaches the epididymis via retrograde spread from the vas deferens, originating from the urethra or bladder. The specific organisms depend on the patient's age, sexual activity, and comorbidities:

Age / Risk Group	Predominant Organisms
Sexually active men <35 yrs	Chlamydia trachomatis, Neisseria gonorrhoeae
Insertive anal intercourse	C. trachomatis, N. gonorrhoeae, enteric Gram-negatives
Men >35 yrs / urinary pathology	E. coli, other enteric/urinary pathogens
Older men >60 yrs	Urinary pathogens; >50% have lower urinary tract obstruction
Children (prepubertal)	Often idiopathic; underlying congenital GU anomaly; neurogenic bladder
Rare causes	M. tuberculosis, Treponema pallidum, fungi, amiodarone toxicity, Behcet syndrome, Brucella

Rosen's Emergency Medicine, pp.1404-1405

Clinical Features

Symptoms

Scrotal pain - characteristically gradual in onset (develops over 24-48 hours, unlike torsion which is abrupt within 4-8 hours)
Pain may initially be referred to the lower abdomen or flank due to inflammation tracking along the vas deferens
Fever (uncommon in isolated epididymitis, more common with orchitis/abscess)
Dysuria, urethral discharge, or other urinary symptoms may be present (though only ~10% with STI-related epididymitis have visible urethral discharge)
Nausea/vomiting from spermatic cord irritation
Associated UTI symptoms (more common in older men)

Signs

Tender, swollen epididymis - initially localized to the epididymis, spreading to the testis over time
Testis in normal anatomic position (cf. high-riding testis in torsion)
Cremasteric reflex intact (absent in torsion)
Scrotal erythema and edema in more advanced cases
Reactive hydrocele may develop
Prehn's sign (pain relief on scrotal elevation) - historically described as positive in epididymitis, but has low sensitivity and specificity and should not be relied upon
A fluctuant scrotum suggests abscess formation
Rosen's Emergency Medicine, pp.1405-1406
Smith and Tanagho's General Urology, p.787

Differential Diagnosis

The most important differential is testicular torsion, which is a surgical emergency. Key distinguishing features:

Feature	Epididymo-Orchitis	Testicular Torsion
Onset	Gradual (24-48 hrs)	Abrupt (exact time recalled)
Fever	Uncommon	Absent
Urinary symptoms	May be present	Absent
Nausea/vomiting	Less common	Sudden, severe
Cremasteric reflex	Intact	Absent
Testis position	Normal	High-riding, horizontal lie
Prehn's sign	Classically positive	Negative
Age peak	Any; puberty, >35 yrs	Neonates, adolescents

Other differentials: torsion of appendix testis ("blue dot" sign), scrotal abscess, herniocoele, orchitis (viral - mumps), varicocele, testicular tumour (10% present with pain from haemorrhage).

Smith and Tanagho's General Urology, pp.787-788
Campbell-Walsh-Wein Urology, pp.2269-2270

Critical point: No single clinical feature reliably excludes torsion. Any equivocal presentation must be managed as torsion until proven otherwise - a missed torsion causes testicular loss.

Investigations

Urinalysis and urine culture - pyuria present in 20-40% of cases; obtain before starting antibiotics
Urethral swab or first-void urine NAAT (nucleic acid amplification test / PCR) for C. trachomatis and N. gonorrhoeae in sexually active men - highest sensitivity
FBC - leucocytosis may be present but is nonspecific; does not differentiate from torsion
Scrotal Doppler Ultrasound - primary imaging modality:
- Enlarged, hypoechoic epididymis with increased blood flow on Doppler (epididymitis)
- Reactive hydrocele may be seen
- If torsion is suspected: absence of testicular flow, spermatic cord twist sign
- Note: severe orchitis can reduce testicular flow, potentially mimicking torsion

Scrotal Doppler US showing enlarged epididymis with increased blood flow (white arrow)

Doppler ultrasound showing enlarged epididymis with increased vascularity (white box) - from Rosen's Emergency Medicine

Renal US + cystography/VCUG in prepubertal boys with recurrent epididymitis - to detect underlying urinary tract anomalies (found in up to 47% of prepubertal boys in some series)

Rosen's Emergency Medicine, pp.1405-1406
Campbell-Walsh-Wein Urology, pp.2396-2398

Management

Antibiotic Therapy

Empirical therapy is guided by the most likely causative organism:

Clinical Scenario	First-line Regimen
Presumed STI (sexually active man, any age)	Ceftriaxone 500 mg IM single dose + Doxycycline 100 mg PO BD x 10-14 days
Presumed enteric organism (older man, urinary pathology)	Levofloxacin 500 mg PO OD x 10 days OR Ofloxacin 300 mg PO BD x 10 days
STI + enteric risk (insertive anal intercourse)	Ceftriaxone 500 mg IM single dose + Levofloxacin 500 mg PO OD x 10 days
IV therapy (febrile, toxic, unable to tolerate PO)	Hospitalise; IV ceftriaxone ± fluoroquinolone; switch to oral when improving

EAU guidelines recommend ceftriaxone 500 mg IM + doxycycline 200 mg as first dose for STI-presumed cases.

Rosen's Emergency Medicine, pp.1406; Tintinalli's Emergency Medicine, p.[Table 93-2]

Adjunct / Supportive Care

NSAIDs (e.g., ibuprofen) - reduce inflammation and pain
Scrotal support (supportive underwear or elevation)
Rest and ice packs
Abstinence from sexual intercourse until both the patient and partner(s) have completed treatment (STI-related cases)
Partner notification and treatment even if partner cultures are negative

Indications for Hospitalisation

Fever / systemic toxicity
Inability to take oral antibiotics
Suspected abscess (requires surgical drainage or orchiectomy)
Immunocompromised patients

Special Considerations

Testicular abscess: If abscess develops from untreated/progressive infection, surgical drainage or orchiectomy may be needed
Tuberculosis: Antituberculous therapy; if no resolution in 2 months, epididymectomy or orchiectomy; chronic involvement characterised by lower pole epididymal swelling, beading of the vas, possible "cold" abscess
Children: Broad-spectrum antibiotics with Gram-negative coverage if pyuria present; in absence of UTI, symptoms may resolve without antibiotics
Viral orchitis (Mumps): Supportive only; occurs in 20-30% of post-pubertal males with mumps; main complication is testicular atrophy potentially causing infertility if bilateral
Bailey and Love's Surgery, pp.1326-1336; Rosen's Emergency Medicine, p.1406

Complications

Complication	Notes
Testicular abscess	Requires drainage or orchiectomy
Infertility	Bilateral involvement, tubular obstruction
Chronic epididymitis	Persistent/recurrent pain; quinolones or doxycycline x 4-6 weeks; epididymectomy if refractory (50% continue pain post-surgery)
Testicular atrophy	Especially in mumps orchitis
Sepsis	Rare but life-threatening; IV antibiotics, hospitalisation
Reactive hydrocele	Usually resolves with treatment

Bailey and Love's Surgery, p.1328; Rosen's Emergency Medicine, p.1404

Epididymo-Orchitis vs Isolated Epididymitis

In most bacterial infections, the testis is secondarily involved once epididymal infection is established, making epididymo-orchitis the more accurate term for the majority of cases. Isolated orchitis without epididymal involvement is rare in bacterial disease but common in viral infections (mumps, coxsackievirus, EBV, varicella). Immunocompromised patients may develop orchitis from mycobacteriosis, cryptococcosis, toxoplasmosis, or candidiasis.

Tintinalli's Emergency Medicine, p.[Orchitis section]; Schwartz's Principles of Surgery, p.1789

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