What is the differential diagnosis for a patient presenting with scrotal edema?

Differential Diagnosis for Scrotal Edema

The differential diagnosis for scrotal edema includes testicular torsion (surgical emergency), epididymitis/epididymo-orchitis (most common in adults), torsion of testicular appendage (most common in prepubertal boys), acute idiopathic scrotal edema, segmental testicular infarction, hydrocele, varicocele, scrotal trauma, and testicular malignancy. 1, 2

Age-Stratified Differential Considerations

The most likely diagnosis varies significantly by patient age:

Adults (>25 years)

• Epididymitis/epididymo-orchitis is overwhelmingly the most common cause, representing approximately 600,000 cases annually in the United States 2
• Testicular torsion becomes rare after age 35 2
• Hydrocele and varicocele are common benign findings 3
• Testicular malignancy should be considered, particularly with painless swelling 3

Adolescents and Young Adults

• Testicular torsion is a critical consideration with bimodal peaks in neonates and postpubertal boys (incidence 2.9-3.8 per 100,000 boys under 18 years) 2
• Epididymitis remains common in this age group 2
• Torsion of testicular appendage occurs frequently 2

Prepubertal Boys

• Torsion of testicular appendage is the most common cause of testicular pain 2
• The "blue dot sign" is pathognomonic but only seen in 21% of cases 2
• Testicular torsion still requires urgent exclusion 2

Key Clinical Distinguishing Features

Testicular Torsion (Surgical Emergency)

• Abrupt onset of severe scrotal pain developing within minutes 2, 4
• Pain accompanied by nausea and vomiting 4
• Negative Prehn sign: pain NOT relieved when testicle is elevated 2, 4
• Normal urinalysis does NOT exclude torsion 2
• Critical time window: 6-8 hours before permanent ischemic damage occurs 2, 4

Epididymitis/Epididymo-orchitis

• Gradual onset of pain over hours to days 2
• May have abnormal urinalysis, though normal urinalysis does not exclude diagnosis 2
• Positive Prehn sign (pain relief with elevation) may be present 2
• Enlarged epididymis with increased blood flow on Doppler ultrasound 1

Acute Idiopathic Scrotal Edema

• Rare, self-limiting condition primarily affecting prepubertal boys but can occur in adults 1, 5, 6
• Usually painless or minimally painful with marked scrotal wall thickening 1, 5
• Erythema and swelling may extend to perineum, abdomen, or penis 5
• Diagnosis of exclusion with normal vital signs, urinalysis, and white blood cell count 5
• Resolves spontaneously within 1-3 days without sequelae 5, 6
• Ultrasound shows heterogeneous striated edematous scrotal wall with increased vascularity, but normal testes and epididymis 1, 7

Segmental Testicular Infarction

• Classic wedge-shaped avascular area on ultrasound 1, 2
• May present as round lesions with variable Doppler flow 1
• MRI can be helpful if ultrasound is equivocal 1

Scrotal Trauma

• Clear history of trauma 3
• May result in testicular hematoma 3
• Ultrasound evaluation essential to assess testicular integrity 3

Diagnostic Algorithm

High Clinical Suspicion (TWIST score >5)

• Immediate urological consultation without imaging 1, 2
• Proceed directly to surgical exploration 2

Intermediate Clinical Suspicion (TWIST score 1-5)

• Urgent Duplex Doppler ultrasound of scrotum 2
• Grayscale examination to identify "whirlpool sign" of twisted spermatic cord (96% sensitivity) 1, 2
• Color Doppler assessment of testicular perfusion (sensitivity 96-100%, specificity 84-95%) 1, 2, 3
• Power Doppler particularly useful for prepubertal testes with slow flow 1
• Use contralateral asymptomatic testicle as internal control 2

Low Clinical Suspicion

• Duplex Doppler ultrasound remains appropriate to identify alternative diagnoses 2
• Consider urinalysis and urine culture for suspected epididymitis 2

Critical Clinical Pitfalls

Overlapping Presentations

• Significant overlap exists between different causes of acute scrotal pain, making clinical diagnosis challenging 2
• A testicle can torse and spontaneously detorse, creating confusing clinical pictures 8

False-Negative Doppler Evaluations

• Can occur with partial torsion (torsion <450 degrees with diminished but present arterial flow) 2, 4
• Can occur with spontaneous detorsion 2, 4
• When clinical suspicion remains high despite negative ultrasound, proceed to surgical exploration 2

Normal Urinalysis

• Does NOT exclude testicular torsion 2
• Does NOT exclude epididymitis 2

Incidental Findings

• Testicular malignancy may be incidentally diagnosed during evaluation for acute symptoms (92% sensitivity, 95% specificity on ultrasound) 3
• Always perform complete bilateral scrotal examination 3

Additional Differential Considerations

• Hydrocele: transillumination positive, fluid collection around testis 3
• Varicocele: "bag of worms" appearance, more common on left side 3
• Inguinal hernia: may present with scrotal swelling, reducible mass 8
• Orchitis: severe testicular inflammation, may lead to rapid testicular damage 4