What are the differential diagnoses (DDs) for a patient presenting with diffuse scrotal edema?

Differential Diagnoses for Diffuse Scrotal Edema

The differential diagnosis for diffuse scrotal edema includes testicular torsion (surgical emergency), epididymitis/epididymo-orchitis, acute idiopathic scrotal edema, torsion of testicular appendage, and segmental testicular infarction, with the specific diagnosis depending on age, onset pattern, and ultrasound findings. 1, 2

Age-Stratified Differential Considerations

Prepubertal Boys (Most Common)

• Torsion of testicular appendage: Most common cause of testicular pain in prepubertal boys, characterized by normal testicular perfusion with localized hyperemia near the appendage 1
• Acute idiopathic scrotal edema (AISE): Primarily affects prepubertal boys but can occur in adults, usually painless or minimally painful with marked scrotal wall thickening 1, 2
  • Self-limited condition with heterogeneous striated appearance of scrotal wall on ultrasound 1
  • "Fountain sign" on color Doppler shows equal arterial blood supply to both testicles 3
  • Symptoms resolve within 48-72 hours with conservative management 4, 3

Adolescents and Young Adults

• Testicular torsion: Bimodal distribution with peak in postpubertal boys, characterized by abrupt onset of severe scrotal pain 1, 2
  • Requires surgical intervention within 6-8 hours to prevent permanent testicular loss 1, 2
  • Decreased or absent blood flow on Doppler ultrasound with "whirlpool sign" of twisted spermatic cord 1, 2
• Epididymitis/epididymo-orchitis: Can occur in adolescents, characterized by gradual onset of pain 1
  • Enlarged epididymis with increased blood flow on color Doppler 1

Adults (Over 25 Years)

• Epididymitis/epididymo-orchitis: Most common cause in adults, representing approximately 600,000 cases annually in the United States 1
  • Gradual onset of pain with enlarged epididymis showing increased blood flow on Doppler 1, 2
  • May have abnormal urinalysis, though normal urinalysis does not exclude diagnosis 1
• Segmental testicular infarction: Median age 37-38 years, presents with classic wedge-shaped avascular area on ultrasound 1
• Acute idiopathic scrotal edema: Rare in adults but documented in patients up to 40 years old 4, 5

Critical Diagnostic Algorithm

Initial Clinical Assessment

• Onset timing: Abrupt onset suggests testicular torsion; gradual onset suggests epididymitis or inflammatory conditions 1, 2
• Pain characteristics: Severe pain with negative Prehn sign (pain not relieved with elevation) indicates torsion 1
• Scrotal wall involvement: Marked scrotal wall thickening without testicular involvement suggests AISE 1, 2

Imaging Protocol (First-Line)

Duplex Doppler ultrasound is mandatory for all cases of scrotal edema 2

1. Grayscale examination (96% sensitivity for torsion) 1, 2:

   • Assess testicular homogeneity and size
   • Look for "whirlpool sign" of twisted spermatic cord
   • Evaluate scrotal wall thickening pattern

2. Color Doppler assessment (96-100% sensitivity for torsion) 1, 2:

   • Compare testicular perfusion to contralateral side
   • Increased flow indicates epididymitis/orchitis
   • Decreased or absent flow indicates torsion

3. Power Doppler (particularly useful in prepubertal boys with slow flow) 1, 2:

   • More sensitive for low-flow states
   • Essential for detecting subtle perfusion differences

Specific Ultrasound Findings by Diagnosis

Testicular Torsion 1:

• Decreased or absent testicular blood flow
• "Whirlpool sign" on grayscale (96% sensitivity)
• Enlarged heterogeneous testis appearing hypoechoic
• Ipsilateral hydrocele and scrotal skin thickening

Epididymitis/Epididymo-orchitis 1:

• Enlarged epididymis with increased blood flow on color Doppler
• Scrotal wall thickening and hydrocele
• Up to 20% concomitant orchitis rate

Acute Idiopathic Scrotal Edema 1, 3:

• Marked scrotal wall thickening with heterogeneous striated appearance
• Increased peritesticular blood flow but normal testicular vascularity
• "Fountain sign" showing equal bilateral testicular perfusion
• Normal testicular parenchyma homogeneity

Segmental Testicular Infarction 1:

• Wedge-shaped avascular focal area on ultrasound
• May also appear as round lesions with variable Doppler flow

Critical Pitfalls to Avoid

• False-negative Doppler occurs in 30% or more of cases, particularly with partial torsion, spontaneous detorsion, or early presentation 1
• Normal urinalysis does not exclude testicular torsion 1, 2
• Prepubertal boys normally have reduced intratesticular blood flow, which can lead to false-positive evaluations for torsion 1
• Clinical examination alone is unreliable due to significant overlap in presentation between different causes 2
• When clinical suspicion for torsion remains high despite normal ultrasound, immediate surgical exploration should proceed 1, 2

Management Based on Diagnosis

Surgical Emergency (Testicular Torsion)

• Immediate urological consultation and surgical exploration within 6-8 hours 1, 2
• High TWIST score (≥6) requires urgent surgical exploration even without imaging 2

Conservative Management (AISE)

• Expectant management with NSAIDs for inflammation 4
• Symptoms resolve within 48-72 hours 4, 3, 6
• No surgical intervention required once diagnosis confirmed 3, 5

Medical Management (Epididymitis)

• Bed rest, scrotal elevation, analgesics 1
• Appropriate antibiotic therapy based on age and risk factors 1