Reproductive · Infectious Disease
The facts most likely to be tested
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Prehn sign is a classic clinical finding where scrotal elevation provides pain relief in epididymitis, helping to distinguish it from testicular torsion.
Chlamydia trachomatis and Neisseria gonorrhoeae are the most common pathogens in men younger than 35 years old.
Enterobacteriaceae (e.g., E. coli) are the most common pathogens in men older than 35 years old or those with bladder outlet obstruction.
Doppler ultrasound is used primarily to rule out testicular torsion; it adds little toward confirming epididymitis, and a negative study does not exclude the diagnosis, which remains clinical.
Ceftriaxone plus Doxycycline is the empiric treatment regimen for patients at risk for sexually transmitted infections.
Levofloxacin 500 mg daily for 10 days is the preferred empiric treatment for patients at low risk for sexually transmitted infections (enteric organisms).
Cremasteric reflex remains intact in epididymitis, whereas it is typically absent in cases of testicular torsion.
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A 28-year-old male presents to the urgent care clinic with a 3-day history of gradual onset left-sided scrotal pain and swelling. He reports associated dysuria and frequency. On physical exam, the left hemiscrotum is tender and indurated at the posterior aspect. Scrotal elevation results in significant pain relief. The cremasteric reflex is present bilaterally.
What is the most likely diagnosis and the most appropriate empiric antibiotic therapy?
Epididymitis; Ceftriaxone and Doxycycline.
The patient's presentation of gradual pain, positive Prehn sign, and intact cremasteric reflex points to epididymitis, and his age group necessitates coverage for common STIs.
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High yield triage
Etiology / Epidemiology
Age <35: Chlamydia trachomatis or Neisseria gonorrhoeae. Age >35: E. coli (enteric organisms).
Clinical Manifestations
Gradual onset unilateral scrotal pain and swelling. Prehn sign: relief with scrotal elevation.
Diagnosis
Scrotal ultrasound with Doppler is the practical test to rule out torsion, but partial cord torsion can mimic epididymitis, so equivocal cases are decided clinically; epididymitis itself is diagnosed clinically plus urethral Gram stain or urine WBCs and NAAT.
Treatment
STI risk: Ceftriaxone + Doxycycline. Enteric risk only (older men, BPH, instrumentation): Levofloxacin. Insertive anal sex: Ceftriaxone + Levofloxacin. Fluoroquinolones carry a boxed warning for tendinitis, tendon rupture, peripheral neuropathy, and CNS effects.
Prognosis
Most resolve with antibiotics; infertility is a rare but serious long-term complication.
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Epidemiology & Etiology
In men <35, it is primarily a sexually transmitted infection caused by Chlamydia trachomatis, Neisseria gonorrhoeae, or Mycoplasma genitalium. In men >35, it is typically associated with bladder outlet obstruction or BPH leading to retrograde flow of infected urine. Rare non-infectious cases are caused by amiodarone.
Pertinent Anatomy
The epididymis is a coiled tube located on the posterior aspect of the testis. Inflammation here causes localized tenderness distinct from the testis itself.
Pathophysiology
Infection typically spreads via the vas deferens from the urethra or bladder. The resulting inflammatory response causes edema, which can lead to testicular ischemia if the pressure is high enough to compress the testicular artery.
Clinical Manifestations
Patients present with unilateral scrotal pain, swelling, and tenderness. Prehn sign (relief with elevation) is classic but not diagnostic. Red flags include high fever, severe systemic toxicity, or abscess formation requiring surgical drainage.
Diagnosis
Scrotal ultrasound is the practical first test to exclude torsion (radionuclide scrotal scanning is the most accurate but is rarely available), and partial cord torsion can mimic epididymitis on ultrasound, so equivocal cases are decided clinically; it shows increased blood flow (hyperemia) and enlarged epididymis. Urinalysis and NAAT for gonorrhea/chlamydia are mandatory for etiology.
Treatment
When an STI is likely (typically men <35): Ceftriaxone 500mg IM once (1 g if the patient weighs 150 kg or more) plus Doxycycline 100mg BID for 10 days. When enteric organisms are likely (typically men >35, BPH, or recent instrumentation): Levofloxacin 500mg daily for 10 days. When both are possible, as in men who practice insertive anal sex: Ceftriaxone 500mg IM once plus Levofloxacin 500mg daily for 10 days. Sex partners from the preceding 60 days should be referred for evaluation and treatment, and patients should abstain from sex until they and their partners have completed therapy and symptoms have resolved. Fluoroquinolones carry a boxed warning for tendinitis and tendon rupture, peripheral neuropathy, CNS effects, and worsening of myasthenia gravis, plus an FDA warning for aortic aneurysm and dissection.
Prognosis
Most patients improve within 48-72 hours of therapy. Chronic pain or infertility due to scarring are the primary long-term concerns.
Differential Diagnosis
Testicular Torsion: absent cremasteric reflex and decreased flow on Doppler
Orchitis: testicular swelling often associated with mumps
Inguinal Hernia: bowel sounds in the scrotum
Hydrocele: painless, transilluminates on exam
Spermatocele: painless, cystic mass at the epididymal head