Epididymitis refers to inflammation of the epididymis while orchitis refers to inflammation of one or both of the testicles. Epididymo-orchitis of course then refers to inflammation of both the epididymis and testes. Isolated epididymitis occurs more frequently as compared to epididymo-orchitis. However, both isolated epididymitis and epididymo-orchitis occur far more frequently than isolated orchitis, which rarely occurs.
There is a bimodal age distribution as it affects both young males aged 15-30 years old (especially if sexually active) and as well as around >60 years old. We will discuss the mechanisms behind both of these distributions.
Anatomy and pathophysiology
The testes are elipsoid structures made up of approximately 250 lobules. These lobules contain the seminiferous tubules which are lined by the Sertoli cells that aid spermatogenesis. The interstitial tissue that covers the seminiferous tubules is lined with Leydig cells - the cells that are responsible for testosterone synthesis. The seminiferous tubules then form straight tubules → rete testis → efferent ductules → epididymis. The epididymis has a head, body and tail before leading into the vas deferens. The seminiferous tubules are enveloped in the fibrous structure known as the tunica albuginea. This is further encased in the serous membrane known as the tunica vaginalis which derives from the abdominal peritoneum and descends through the superficial inguinal ring before ending up in the scrotum.
The epididymis is found on the posterolateral side of the testis. The function of the epididymis is to store spermatozoa and allow them to continue maturation prior to ejaculation.
Epididymitis due to retrograde passage of an infection from the bladder or urethra. It travels through the ejaculatory ducts → vas deferens → reaching the tail of the epididymis before reaching the head of the epididymis. The inflammation concurrently involves the testis leading to the orchitis simultaneously.
The pathogenesis may differ between pre-pubertal boys, sexually active males (14-35 years old), and older males (>60 years).
- Pre-pubertal boys
- Recent viral infection (such as adenovirus, enterovirus)
- Reflux of urine into the ejaculatory ducts. It occurs with associated structural urogenital abnormalities.
- UTI causing organisms such as (E. coli, pseudomonas aeruginosa, proteus spp.). This may occur with structural or functional urinary tract abnormalities.
Refers mainly to children (≤1 years old). The pathophysiology behind this group is uncertain in 25% of cases but it may be due to:
- Males aged 14-35
The origin of the infection is most likely to be due to a sexually transmitted infection (STI). The most common causative agents being Chlamydia trachomatis, Neisseria gonorrhoeae and Mycoplasma genitalium.
It may also be due to an enteric organism in cases of anal sex.
- Elderly males
This is often due to bladder outflow obstruction that occurs due to prostatic enlargement leading to a UTI that subsequently disseminates into epididymo-orchitis. The pathogens implicated are enteric pathogens usually.
Other causes of epididmyitis/orchitis may be:
- Tuberculosis
- Brucellosis
- Candidiasis
- Mumps (mumps causes epididymitis/orchitis in 38% of infected men). Mumps also tends to affect just the testicle and not the epididymis (i.e. isolated orchitis).
- Drug-induced - due to amiodarone (but the mechanism is poorly understood)
- Vasculitic causes - as seen Henoch-Schönlein purpura (HSP) or Behçet’s syndrome.
- Idiopathic
⚠️ Risk factors
- Unprotected sex
- Bladder outflow obstruction - as seen in BPH, for example.
- Urinary tract instrumentation - such as cystoscope or catheterisation.
- Insertive anal intercourse
- Vasculitis such as HSP or Behçet’s syndrome
- Amiodarone use
- Mumps
- Tuberculosis exposure
😷 Presentation
Epididymo-orchitis typically presents with gradual onset of symptoms over minutes-hours.
Symptoms may include:
- Unilateral pain and swelling of the testicle and epididymis
- Tenderness and warmth on palpation of the scrotum
- Dysuria
- Urethral discharge - this is suggestive of an STI pathogen
- Dragging/heavy sensation
- Lower urinary tract symptoms - which can be classified as voiding or storage symptoms.
- Fever and systemic symptoms - indicates an infectious cause.
- Positive Prehn’s sign - this is when there is scrotal pain that is relieved on elevation of the scrotum. However, this is an unreliable sign as it lacks specificity
- Normal crremasteric reflex
- Enlarged/tender prostate - if there is concurrent prostatitis and/or BPH.
🔍 Investigations
- STI screening via NAAT - the sample should be collected via first-void urine (assessing for Chlamydia trachomatis, Neisseria gonorrhoeae and Mycoplasma genitalium). This is typically done in younger patients as this is more likely to be the cause
- Urinalysis and MC&S - it may show signs indicative of UTI. This is typically done in older patients as this is more likely to be the cause.
- Scrotal Doppler ultrasound - it is not routinely done but it is used to exclude testicular torsion. For epididymitis it may show increased blood flow.
- Saliva swab and serum antibodies (IgM) for mumps.
Further investigations may be performed (especially in children) to exclude any underlying structural abnormalities.
🧰 Management
Management depends on if the organism is likely to be an STI or an enteric organism. However, we can always provide symptomatic management with analgesics.
- Urgent referral to sexual health clinic.
- Ceftriaxone (500mg IM single dose) + doxycycline (100mg BD orally for 10-14 days)
- + Azithromycin (1g PO single dose) should be added if gonorrhoea is likely.
- Counsel patients on sexual abstinence (until antibiotic course is completed and symptoms resolve) and use of barrier contraception.
- Urinalysis and MC&S - as mentioned above.
- Ofloxacin - or another oral fluoroquinolone. This is an empirical treatment, given for 2 weeks.
🚨 Complications
- Abscess formation
- Testicular infarction/ischaemia
- Chronic pain
- Infertility