Acute epididymitis

1. Definition and Overview

Acute epididymitis is the inflammation of the epididymis, typically of sudden onset, often caused by infection. It may involve adjacent testicular tissue (termed epididymo-orchitis). It is a common urological condition in adult males and can cause significant pain and swelling.

2. Cause and Etiology

The etiology of acute epididymitis varies by age, sexual activity, and underlying urological abnormalities.

A. Infectious Causes (Most Common)

Sexually Transmitted Pathogens (Younger men, <35 years):

Chlamydia trachomatis
Neisseria gonorrhoeae

Enteric Pathogens (Older men, children, or men with urinary tract abnormalities):

Escherichia coli
Pseudomonas aeruginosa
Klebsiella species

Other Pathogens:

Ureaplasma urealyticum, Mycoplasma genitalium
Viral: Mumps (especially in children or adolescents)
Tuberculosis (TB): Chronic granulomatous epididymitis
Brucellosis: In endemic regions

B. Non-Infectious Causes

Post-procedural inflammation (e.g., following catheterization or surgery)
Reflux of sterile urine into the ejaculatory ducts (e.g., due to heavy lifting or straining)
Amiodarone-induced epididymitis (due to drug accumulation in the epididymis)

3. Pathophysiology

Ascending Infection:

Pathogens typically ascend from the urethra → vas deferens → epididymis.
This leads to inflammation, edema, and congestion of the epididymal tubules.
Neutrophilic infiltration causes tissue damage and swelling.

Complications:

Spread to the testis: epididymo-orchitis
Abscess formation
Testicular infarction (rare but serious)
Fibrosis and chronic pain
Infertility due to ductal obstruction

4. Epidemiology

Common age groups:

<35 years: more likely STI-related

o 35 years: more likely due to urinary tract pathogens

Incidence:

Accounts for >600,000 cases annually in the United States.
More common than testicular torsion in adults.

Risk Factors:

Unprotected sexual activity (especially with multiple partners)
Recent urinary tract instrumentation (e.g., catheterization)
Structural urological anomalies (e.g., prostatic hypertrophy)
Receptive anal intercourse (increased enteric pathogen risk)

5. Clinical Presentation

A. Symptoms

Unilateral scrotal pain and swelling (usually develops over a few days)
Pain may radiate to the inguinal region or flank
Fever, chills, malaise (in more severe cases)
Dysuria, urethral discharge (if sexually transmitted)
Pain relief with scrotal elevation (Prehn's sign; though nonspecific)

B. Physical Examination

Tender, swollen epididymis
Testis may be difficult to distinguish if orchitis is present
Reactive hydrocele often accompanies inflammation
Cremasteric reflex is preserved (unlike testicular torsion)

6. Imaging Features

A. Ultrasound with Color Doppler (Modality of choice)

Findings:

Enlarged, hypoechoic epididymis (typically head and tail)
Increased vascularity (hyperemia) on Doppler
Associated testicular involvement: orchitis
Reactive hydrocele or scrotal wall edema
In severe cases, abscess formation (heterogeneous, hypoechoic collections)

Differential Diagnosis:

Testicular torsion: no or reduced blood flow in the testis
Tumor: mass without hyperemia or inflammatory signs
Inguinal hernia: bowel loops in the scrotum
Hydrocele/varicocele: distinguish by location and flow

7. Laboratory Tests

Urinalysis:

Pyuria, bacteriuria, hematuria

Urine culture
Urethral swab/PCR for Chlamydia and Gonorrhea
CRP and ESR: Elevated in systemic inflammation
STI screening (HIV, syphilis)

8. Treatment

A. Antibiotic Therapy

Empiric therapy based on age and risk:

Age <35 years or STI risk:

Ceftriaxone 500–1000 mg IM once
+ Doxycycline 100 mg BID for 10 days

Age >35 years or low STI risk:

Levofloxacin 500 mg once daily for 10 days
Or Ofloxacin 300 mg BID

Enteric organisms (e.g., E. coli):

Trimethoprim-sulfamethoxazole or fluoroquinolones

B. Supportive Measures

Scrotal elevation and support
Cold compresses
Analgesia/NSAIDs
Rest and hydration

C. Invasive Intervention

Abscess drainage (if abscess is confirmed)
Orchiectomy (rare, for severe necrotizing infection or infarction)

9. Prognosis

A. General Prognosis

Most cases resolve completely with appropriate antibiotic therapy.
Symptomatic improvement is usually seen in 1–3 days.
Full resolution may take 2–4 weeks.

B. Complications

Recurrent epididymitis
Chronic scrotal pain
Abscess or testicular infarction
Infertility (especially in bilateral or untreated cases)
Fibrosis and chronic obstruction of spermatic ducts

10. Prevention

Safe sexual practices: condom use, STI testing
Avoid unnecessary catheterization
Early treatment of urinary tract infections
Patient education on genital hygiene

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Case study: 28-Year-Old Male Presenting with Right Testicular Pain
Acute Epididymitis

History and Imaging

A 28-year-old male with a history of sexually transmitted infections presented with a 1–2 day history of right testicular pain.
His partner was recently diagnosed with gonorrhea and chlamydia.
Below are ultrasound images of the right scrotum, including color Doppler images focusing on the right epididymis and a comparative view of both testes using color Doppler.

Quiz 1

What is the most prominent abnormal finding?
(1) Epididymitis
(2) Testicular torsion
(3) Orchitis
(4) Testicular abscess
This condition is the most common cause of acute testicular pain in adult males.
(1) True
(2) False
This condition shows a bimodal age distribution.
(1) True
(2) False
Explanation: The incidence of this condition varies based on differences in microbiological etiology and associated risk factors.
Which clinical sign best differentiates this condition from acute torsion?
(1) Dysuria
(2) Tenderness localized to the epididymis
(3) Increased echogenicity of the epididymis
(4) Increased peritesticular perfusion

Findings and Diagnosis

Findings
Ultrasound examination revealed an enlarged and heterogeneously echogenic epididymal head and tail with associated swelling and hypervascularity. No discrete testicular mass was identified.

Differential Diagnosis

Orchitis
Testicular abscess
Testicular torsion
Testicular trauma

Final Diagnosis: Epididymitis

Discussion

Acute Epididymitis
Epididymitis and epididymo-orchitis are the most common causes of acute scrotal pain in adult males. The condition may involve the entire epididymis or be localized to a segment.

Pathophysiology
The most common causative organisms are Escherichia coli, Pseudomonas aeruginosa, and the sexually transmitted pathogens Neisseria gonorrhoeae and Chlamydia trachomatis. This is a retrograde infection typically starting in the tail of the epididymis, progressing toward the head, and potentially spreading to the testis, resulting in secondary orchitis.

Epidemiology
In the United States, more than 600,000 cases of epididymitis or epididymo-orchitis are reported annually. These conditions account for approximately 28.7% of all cases of acute scrotal pain.

Clinical Presentation
Patients typically present with dysuria, right testicular pain, swelling, and occasionally erythema of the scrotal skin.

Imaging Findings

Enlarged, hypoechoic epididymal head and body
Increased blood flow on Doppler ultrasound
Scrotal wall thickening
Presence of hydrocele
Abscess formation (rare)
Orchitis was observed in approximately 20% of cases

Treatment
Uncomplicated cases are typically managed with antibiotics.

References

(1) Aganovic L, Cassidy F. Imaging of the scrotum. Radiol Clin North Am. 2012;50(6):1145-1165.

(2) Bertolotto M, Cantisani V, Valentino M, Pavlica P, Derchi LE. Pitfalls in imaging for acute scrotal pathology. Semin Roentgenol.2016; 51(1):60-69.

(3) Boettcher M, Bergholz R, Krebs TF, et al. Differentiation of epididymitis and appendix testis torsion by clinical and ultrasound signs in children. J Urol. 2013;82(4):899-904.

(4) Bourke MM, Silverberg JZ. Acute scrotal emergencies. Emerg Med Clin North Am. 2019;37(4):593-610.

(5) Velasquez J, Boniface MP, Mohseni M. Acute scrotum pain. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan. 2022 May 15.

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