Infectious Disease · Genitourinary Infections
The facts most likely to be tested
Mumps orchitis is the most common viral cause of orchitis, typically occurring in post-pubertal males 4 to 8 days after the onset of parotitis.
Bacterial orchitis in men younger than 35 years is most commonly caused by Chlamydia trachomatis or Neisseria gonorrhoeae via retrograde spread from the urethra.
Bacterial orchitis in men older than 35 years is most commonly caused by Escherichia coli or other enteric organisms associated with benign prostatic hyperplasia (BPH).
Prehn sign (relief of pain with scrotal elevation) is classically positive in epididymo-orchitis but negative in testicular torsion.
Color Doppler ultrasonography is the diagnostic test of choice to confirm inflammation and exclude testicular torsion in patients with acute scrotal pain.
Testicular torsion is the most critical differential diagnosis to rule out, characterized by a high-riding testis and an absent cremasteric reflex.
Treatment for bacterial orchitis involves ceftriaxone plus doxycycline for younger patients, or fluoroquinolones for older patients with suspected enteric pathogens.
Vignette unlocked
A 22-year-old male presents to the urgent care clinic with a 3-day history of unilateral testicular pain and swelling. He reports a recent history of bilateral parotid gland swelling and fever that resolved one week ago. Physical examination reveals a tender, enlarged testis and a normal cremasteric reflex. Scrotal ultrasound demonstrates increased blood flow to the affected testis and associated epididymitis.
What is the most likely etiology of this patient's condition?
Mumps virus (Paramyxovirus)
The patient's history of recent parotitis followed by orchitis is classic for mumps, which is a viral cause of orchitis that typically presents with increased blood flow on Doppler ultrasound, distinguishing it from the decreased flow seen in testicular torsion.
Full handout
High yield triage
Etiology / Epidemiology
Viral etiology is most common in prepubertal boys, specifically mumps. Bacterial cases are usually secondary to epididymitis in sexually active men.
Clinical Manifestations
Presents with unilateral testicular pain and swelling. Prehn sign is typically negative; Phren sign is not reliable for distinguishing from torsion.
Diagnosis
Clinical diagnosis is standard. Testicular ultrasound with Doppler is the gold standard to rule out torsion.
Treatment
Viral: supportive care. Bacterial: Ceftriaxone plus Doxycycline. Avoid fluoroquinolones in children.
Prognosis
Most recover fully. Infertility and testicular atrophy are the primary long-term risks.
Full handout
Epidemiology & Etiology
Viral orchitis is most frequently associated with the mumps virus, typically occurring 4-10 days after parotitis. Bacterial orchitis is almost always an extension of epididymitis caused by *Chlamydia trachomatis* or *Neisseria gonorrhoeae* in men <35. In older men, it is often associated with bladder outlet obstruction and enteric organisms like *E. coli*.
Pertinent Anatomy
The testis is encased in the tunica albuginea, which limits expansion during inflammation, leading to severe pain. The epididymis is anatomically contiguous, facilitating the spread of infection from the vas deferens.
Pathophysiology
Viral infection causes direct Leydig cell damage and interstitial edema. Bacterial infection spreads via the vas deferens in a retrograde fashion. The resulting inflammatory response causes testicular ischemia due to increased intratesticular pressure.
Clinical Manifestations
Patients present with acute onset of scrotal pain, erythema, and edema. Prehn sign (relief of pain with scrotal elevation) is classically negative. Red flags include high fever, systemic toxicity, or a high-riding testis which mandates immediate surgical exploration to rule out testicular torsion.
Diagnosis
Diagnosis is primarily clinical based on history and physical exam. Testicular ultrasound with Doppler is the gold standard to differentiate orchitis from torsion by demonstrating increased blood flow (hyperemia) in orchitis versus absent flow in torsion.
Treatment
Viral cases require bed rest, NSAIDs, and scrotal support. Bacterial cases require Ceftriaxone (250mg IM) plus Doxycycline (100mg BID x 10 days). Fluoroquinolones are contraindicated in pediatric patients due to cartilage damage. If enteric organisms are suspected in older men, use Levofloxacin.
Prognosis
Most patients recover without sequelae. Testicular atrophy occurs in up to 60% of mumps cases. Infertility is a rare but significant complication, particularly with bilateral involvement.
Differential Diagnosis
Testicular Torsion: absent blood flow on Doppler
Epididymitis: pain localized to the posterior aspect of the testis
Inguinal Hernia: bowel sounds heard on scrotal auscultation
Hydrocele: transilluminates on physical exam
Testicular Tumor: painless, firm, fixed mass