Mumps Orchitis

Mumps orchitis is acute inflammation of one or both testes caused by mumps virus, a paramyxovirus (RNA virus, genus Orthorubulavirus). It is the commonest extrasalivary complication of mumps in post-pubertal males. It affects 15 to 30% of post-pubertal males with mumps (rare before puberty), with onset typically 4 to 8 days after parotitis (range 1 to 3 weeks), and occasionally without parotitis (10% of cases).

Epidemiology

• Mumps incidence has fallen over 99% in countries with routine two-dose MMR vaccination, but outbreaks occur in vaccinated young adults (waning immunity, vaccine effectiveness against mumps about 88% for two doses), in college campuses, closed communities, and unvaccinated populations. Peak ages 15 to 29 in outbreaks.
• Orchitis is bilateral in 10 to 30% of cases.
• Pathogenesis: viraemia seeds the testis, with interstitial oedema, lymphocytic infiltration and seminiferous tubule damage, and increased intratesticular pressure within the tight tunica albuginea, leading to ischaemic injury and atrophy. Epididymitis accompanies in about 85%.

Complications

• Testicular atrophy in about 30 to 50% of affected testes (develops in months), with reduced testosterone and spermatogenesis.
• Oligospermia or azoospermia: impairment of fertility in 13% unilateral and up to 30 to 87% in bilateral disease at some level, but complete sterility is rare (under 10% of bilateral cases), mostly due to the unaffected testis in unilateral disease.
• Reduced testosterone production, hypogonadism (late), and a possible association with testicular tumours.
• Other mumps complications: aseptic meningitis (up to 10%), encephalitis, pancreatitis, oophoritis in women (5%), sensorineural deafness (1 in 20,000), myocarditis, nephritis, arthritis, and thyroiditis.
• Differential includes viral orchitis from other viruses (coxsackievirus B, echovirus, EBV, parvovirus, varicella-zoster), bacterial epididymo-orchitis, testicular torsion, trauma, tumour, brucellosis, tuberculosis, and sarcoidosis.

History: mumps exposure or prior parotitis in the preceding week, unvaccinated or incompletely vaccinated.

Symptoms and signs

• Abrupt onset of unilateral testicular pain, swelling and tenderness, with high fever (39 to 41 degrees Celsius), chills, headache, malaise, nausea and vomiting. Pain may radiate to the groin and lower abdomen.
• Examination: enlarged (up to 3 to 4 times normal size), firm, exquisitely tender testis, erythema and oedema of the scrotal skin, reactive hydrocele, epididymal tenderness, and the Prehn sign is not reliable (relief of pain on elevation may be absent). The cremasteric reflex is preserved (usually absent in torsion).
• Parotitis (bilateral or unilateral swelling of the parotid glands with tenderness, earache, trismus) in most, but may be absent or precede by days, or follow.
• The course lasts 3 to 7 days (fever resolves in 3 to 5 days), with swelling and tenderness subsiding over 1 to 2 weeks (can persist for weeks). Atrophy begins weeks to months later.
• Red flags: sudden onset severe pain without fever (torsion), a high-riding transverse testis, absent cremasteric reflex, rapid progression, signs of abscess, and signs of meningeal irritation (headache, neck stiffness, photophobia) or encephalitis.
• Differential diagnosis: testicular torsion (must be excluded urgently in the acute scrotum, especially in teenage males), bacterial epididymo-orchitis (urinary symptoms, urethral discharge, pyuria), testicular tumour, trauma, inguinal hernia, hydrocele, Henoch-Schönlein purpura, torsion of testicular appendage, vasculitis, and other viral orchitis.

• Diagnosis is clinical in an outbreak or contact setting, and confirmed by laboratory testing:
• Mumps RT-PCR of buccal (parotid duct) swab, throat swab, saliva or urine, ideally within 3 days of parotitis onset (up to 8 to 9 days). Most sensitive and specific, and available through public health laboratories. Also CSF PCR for meningitis.
• Serology: mumps-specific IgM (appears within 5 days of onset, may be absent in vaccinated people), and a fourfold rise in IgG between acute and convalescent sera (2 to 3 weeks apart). IgM may be negative in vaccinated patients, so PCR is preferred.
• Viral culture of throat swab, urine, CSF (limited use).
• Blood tests: white cell count (leukopenia with lymphocytosis, or normal), raised amylase (parotitis or pancreatitis), CRP mildly elevated, raised ESR.
• Urinalysis and urine culture / urethral NAAT to exclude bacterial epididymo-orchitis.
• Scrotal colour Doppler ultrasound: enlarged hypoechoic or heterogeneous testis with increased vascularity (hyperaemia), epididymal enlargement, reactive hydrocele, and scrotal skin thickening. Normal or increased testicular flow distinguishes it from torsion (absent or reduced flow). Use urgently when torsion cannot be excluded.
• Baseline and follow-up fertility assessments: semen analysis at 3 to 6 months, and again at 12 months in bilateral or severe disease, FSH, LH and testosterone for evidence of testicular failure.
• Public health: notification of suspected and confirmed mumps cases, and contact tracing.

No specific antiviral therapy exists. Treatment is supportive, aimed at symptom relief and complications.

Supportive care

• Bed rest until fever and tenderness subside, scrotal elevation and support (briefs, towel roll), cold packs to the scrotum 15 to 20 minutes at a time to reduce swelling and pain, and adequate hydration.
• Analgesics and antipyretics: paracetamol 1 g every 6 hours (maximum 4 g/day) and NSAIDs (ibuprofen 400 to 600 mg every 6 to 8 hours or naproxen 500 mg twice daily) for 5 to 7 days with food. Short-course opioids (codeine, tramadol 50 mg) for severe pain. Spermatic cord block (lidocaine 1% 10 to 20 mL, with or without bupivacaine) for severe, refractory pain.
• Antiemetics (ondansetron 4 mg) when needed.

Other therapies with limited or inconsistent evidence

• Corticosteroids (prednisolone 40 to 60 mg daily for 3 to 5 days) have been used to reduce inflammation and relieve pain, but do not improve atrophy rates, so they are not routinely recommended.
• Interferon alpha-2b (3 million units daily, SC or IM, for 7 days) has been proposed to prevent atrophy and infertility in small trials. It is not standard.
• Surgical decompression (incision of the tunica albuginea, fasciotomy, orchiectomy) is rarely required, and only for refractory pain, abscess formation, or persistent ischaemia.
• Antibiotics are not indicated, unless bacterial superinfection is suspected (ceftriaxone and doxycycline per STI pathway).

Isolation and infection control

• Isolate cases from onset of illness (infectious from 2 days before to 5 days after onset of parotitis). Exclude from school or work for 5 days after onset. Standard and droplet precautions in healthcare settings. Hospital staff without evidence of immunity should avoid contact.
• Notify public health authorities, identify contacts, and vaccinate susceptible contacts (MMR, although it does not prevent disease if given after exposure). A third MMR dose is recommended for people in outbreak settings.

Management of complications

• Meningitis, encephalitis, pancreatitis: supportive. Deafness: audiology, hearing aids, cochlear implantation. Oophoritis: analgesia.
• Fertility and hormone follow-up: semen analysis at 3 to 6 months, testosterone, LH and FSH in bilateral orchitis, sperm banking where appropriate, testosterone replacement for hypogonadism (see male hypogonadism), and fertility treatment (ICSI) if needed. Orchiectomy not usually required. Annual testicular self-examination, since a link with testicular cancer is not established but follow-up is reasonable.

Prevention

• Two doses of MMR vaccine (first at 12 to 15 months, second at 4 to 6 years, or at least 28 days after the first dose), which prevents about 88% of cases and reduces orchitis. Catch-up vaccination of unvaccinated adolescents and adults, particularly males before puberty. In outbreaks, give a third dose to affected groups. MMR is contraindicated in pregnancy and severe immunosuppression.
• Waning immunity in young adults supports booster doses in outbreak settings.

Follow-up

Review at 1 to 2 weeks for symptom resolution and examination of testicular size. Reassess at 3 and 6 months for atrophy and semen quality. Counselling about fertility and that unilateral involvement generally spares fertility, while bilateral involvement carries a higher risk.