What is the differential diagnosis and management for a child with a swollen testicle?

Differential Diagnosis of Swollen Testicle in Children

Primary Differential Diagnoses

The four main causes of acute scrotal swelling in children are testicular torsion (45%), torsion of testicular appendage (35%), epididymitis (15%), and acute idiopathic scrotal edema, with testicular torsion being the surgical emergency that must be ruled out first. 1, 2, 3

1. Testicular Torsion (Surgical Emergency)

• Most critical diagnosis requiring intervention within 6-8 hours to prevent testicular loss 4, 1
• Presents with abrupt onset of severe unilateral scrotal pain and swelling, often with nausea and vomiting 1, 5, 6
• Bimodal age distribution: peaks in neonates and postpubertal boys 1, 7
• Negative Prehn sign (pain NOT relieved by testicular elevation) distinguishes it from epididymitis 1, 5
• Normal urinalysis does NOT exclude torsion 1
• Accounts for 45% of acute scrotal pain cases in children 3

2. Torsion of Testicular Appendage

• Most common cause in prepubertal boys (35% of cases) 1, 5, 3
• Less severe pain than testicular torsion, more gradual onset 1
• "Blue dot sign" (visible through scrotal skin) is pathognomonic but only present in 21% of cases 1
• Ultrasound shows normal testicular perfusion with localized hyperemia near the appendage 1, 5
• Usually managed conservatively with symptomatic treatment 2

3. Epididymitis/Epididymo-orchitis

• Accounts for 15% of pediatric cases (historically considered rare in children) 3
• Gradual onset of pain (key distinguishing feature from torsion) 1
• May have fever and abnormal urinalysis, though normal urinalysis does NOT exclude it 1
• Only 2 of 17 cases in one pediatric series had bacterial UTI 3
• Ultrasound shows enlarged epididymis with INCREASED blood flow on color Doppler 4, 1
• Scrotal wall thickening and hydrocele common 4, 1

4. Acute Idiopathic Scrotal Edema

• Rare, self-limiting condition primarily affecting prepubertal boys 1, 5
• Marked scrotal wall thickening but minimal or no pain (key feature) 1, 5
• Ultrasound shows increased peritesticular blood flow but normal testicular vascularity 1, 5
• Diagnosis of exclusion 1

5. Segmental Testicular Infarction

• Classic wedge-shaped avascular area on ultrasound 1
• May also present as round lesions with variable Doppler flow 1
• Median age 37-38 years (less common in children) 1

Critical Diagnostic Approach

Immediate Clinical Assessment

Any acute scrotal swelling must be treated as testicular torsion until proven otherwise 1, 5

Key clinical features to assess:

• Onset timing: Abrupt (torsion) vs. gradual (epididymitis) 1
• Pain severity: Severe (torsion) vs. moderate (appendage torsion) vs. minimal (idiopathic edema) 1, 5
• Prehn sign: Negative in torsion, positive in epididymitis 1, 5
• Nausea/vomiting: Common in torsion 1, 6
• Fever: Suggests epididymitis but does NOT rule out torsion 1

Imaging Protocol

Duplex Doppler ultrasound is the first-line imaging modality (sensitivity 69-96.8%, specificity 87-100%) 4, 1

Critical ultrasound components:

• Grayscale examination: Look for "whirlpool sign" (96% sensitivity for torsion), heterogeneous testis, hydrocele 4, 1
• Color/Power Doppler: Compare blood flow to contralateral testis (use as internal control) 4, 1
• Power Doppler preferred in prepubertal boys due to normally reduced flow 4, 1
• Spectral Doppler analysis: Assess upper, mid, and lower poles for flow variations 4, 1

Torsion findings:

• Decreased or absent blood flow 4, 1
• "Whirlpool sign" of twisted spermatic cord (most specific sign) 4, 1, 7
• Enlarged heterogeneous hypoechoic testis 4, 1

Epididymitis findings:

• Enlarged epididymis with INCREASED flow (sensitivity nearly 100%) 4, 1

Critical Management Algorithm

High Clinical Suspicion for Torsion

Proceed directly to surgical exploration WITHOUT imaging 1, 5

• Do not delay surgery for ultrasound when clinical suspicion is high 1
• Surgical exploration required in 92% of pediatric acute scrotum cases 3

Intermediate Suspicion

Urgent Duplex Doppler ultrasound 1, 5

• If ultrasound confirms torsion: immediate surgical exploration 1
• If ultrasound normal but clinical suspicion remains high: still proceed to surgical exploration (30% false-negative rate for partial torsion) 1, 5

Confirmed Torsion Management

• Immediate urological consultation and surgical exploration within 6-8 hours 1, 7, 5
• Detorsion and bilateral orchiopexy (to prevent contralateral torsion) 1
• Orchidectomy if testicle completely necrotic 2

Critical Pitfalls to Avoid

False-negative Doppler occurs in 30% or more of cases, particularly with:

• Partial torsion (arterial flow may persist while venous flow obstructed) 4, 1
• Spontaneous detorsion 4, 1
• Early presentation (first few hours when testis may appear normal) 4, 1

False-positive Doppler in infants/young boys who normally have reduced intratesticular blood flow 4, 1

Reactive hyperemia after spontaneous detorsion can mimic epididymitis on Doppler 4

Rare presentation: Perforated appendicitis can present with scrotal swelling via patent processus vaginalis (fewer than 5 reported cases) 8

Special Considerations

Neonatal/Perinatal Torsion

• Extravaginal torsion (different mechanism than older children) 7
• Accounts for approximately 10% of pediatric torsion cases 7
• Immediate surgical exploration recommended if diagnosed after birth 7
• Prenatal torsion shows heterogeneous echotexture with calcifications 7