What are the differential diagnoses and management options for scrotal swelling?

Differential Diagnosis and Management of Scrotal Swelling

Immediate Risk Stratification Based on Clinical Presentation

The most critical priority when evaluating scrotal swelling is to identify or exclude testicular torsion, which requires surgical intervention within 6-8 hours to prevent permanent testicular loss. 1

High-Risk Features Requiring Immediate Urological Consultation

• Abrupt onset of severe scrotal pain in an adolescent or young adult (bimodal peak in neonates and postpubertal boys) suggests testicular torsion and mandates immediate surgical exploration without waiting for imaging 1, 2
• Negative Prehn sign (pain not relieved with testicular elevation) is a key distinguishing feature of torsion 1
• Sudden onset with severe pain when urinalysis and testing do not support urethritis or UTI requires emergency evaluation for torsion 1, 2

Intermediate-Risk Presentation

• Gradual onset of pain with fever, urinary symptoms, or urethral discharge suggests epididymitis/epididymo-orchitis rather than torsion 1, 2
• Obtain urgent Duplex Doppler ultrasound while keeping urology immediately available for intermediate clinical suspicion 1, 2
• Use the TWIST scoring system for risk stratification in pediatric patients (3 months-18 years) 1

Primary Differential Diagnoses by Age Group

Adolescents and Young Adults

Testicular torsion (surgical emergency):

• Abrupt severe pain with decreased or absent testicular blood flow on Doppler ultrasound 1, 2
• "Whirlpool sign" of twisted spermatic cord on grayscale ultrasound (96% sensitivity) 3, 1
• Enlarged heterogeneous hypoechoic testis with ipsilateral hydrocele and scrotal wall thickening 1
• Color Doppler sensitivity 96-100%, but false-negatives occur in 30% of cases with partial torsion 3, 1

Epididymitis/epididymo-orchitis (most common cause in adults):

• Gradual pain onset with enlarged epididymis showing increased blood flow on Doppler 3, 1
• May have abnormal urinalysis, though normal urinalysis does not exclude diagnosis 1, 2
• Scrotal wall thickening and hydrocele common; up to 20% concomitant orchitis 3

Torsion of testicular appendage:

• Most common cause of testicular pain in prepubertal boys 1
• "Blue dot sign" is pathognomonic but only seen in 21% of cases 1

Adults Over 35 Years

Epididymitis/epididymo-orchitis (overwhelmingly most common):

• Approximately 600,000 cases annually in the United States 1
• Testicular torsion is rare in this age group 1

Post-Trauma Presentation

Testicular rupture:

• Scrotal ecchymosis, swelling, and difficulty identifying testicular contours on examination 4, 2
• Loss of testicular contour and heterogeneous echotexture on ultrasound are most specific findings 4
• Requires prompt surgical exploration, debridement, and tunical closure regardless of ultrasound findings to prevent ischemic atrophy and infection 4
• Evaluate for concomitant urethral injury if blood at meatus, hematuria, or inability to void 4, 2

Less Common but Important Diagnoses

Segmental testicular infarction:

• Classic wedge-shaped avascular area on ultrasound, though round lesions with variable flow also reported 3, 1
• MRI can be helpful if ultrasound is equivocal 3

Acute idiopathic scrotal edema:

• Rare, self-limiting condition primarily in prepubertal boys but can occur in adults 3, 1
• Usually painless with marked scrotal wall thickening showing heterogeneous striated edematous appearance with increased vascularity 3, 1
• Normal testes and epididymis without increased vascularity; diagnosis of exclusion 3

Incarcerated inguinal hernia:

• Emergent condition requiring early identification 5

Fournier's gangrene:

• Life-threatening necrotizing fasciitis requiring immediate recognition and surgical debridement 5

Diagnostic Algorithm

Step 1: Clinical Assessment

• Timing of pain onset: Abrupt = torsion; gradual = epididymitis 1, 2
• Patient age: Adolescent = torsion risk; adult >25 = epididymitis more likely 1, 2
• Associated symptoms: Fever, urinary symptoms, discharge suggest infection 2
• Trauma history: Assess for rupture and urethral injury 4, 2

Step 2: Imaging When Appropriate

Duplex Doppler ultrasound is first-line imaging for intermediate suspicion 3, 1, 2:

• Grayscale examination: Identify "whirlpool sign," assess testicular homogeneity 3, 1
• Color Doppler: Assess testicular perfusion (sensitivity 96-100%) 3, 1
• Power Doppler: More sensitive for slow flow, especially useful in prepubertal testes 3, 1
• Use contralateral testis as internal control 1

Step 3: Management Based on Diagnosis

For confirmed or highly suspected torsion:

• Immediate urological consultation and surgical exploration within 6-8 hours of symptom onset 1, 4, 2
• Perform bilateral orchiopexy to prevent contralateral torsion (82% have Bell clapper deformity) 1

For epididymitis/epididymo-orchitis:

• Bed rest, scrotal elevation, analgesics 1, 2
• Empiric antibiotics after obtaining cultures: Ceftriaxone plus Doxycycline for sexually transmitted etiology; Ofloxacin for enteric organisms 2
• Mandatory reevaluation if no improvement within 3 days to exclude tumor, abscess, infarction, or atypical infections 2

For testicular rupture:

• Immediate surgical exploration with debridement and tunical closure when possible; orchiectomy only if non-salvageable 4
• Tunica vaginalis flap or graft if primary closure not possible 4

For conservative management (intratesticular hematoma, scrotal wall hematoma, acute idiopathic scrotal edema):

• Supportive care with scrotal elevation and analgesics 3, 2
• Diuretics may help resolve swelling 6

Critical Pitfalls to Avoid

• Normal urinalysis does not exclude torsion or epididymitis 1, 2
• False-negative Doppler occurs in 30% of cases with partial torsion or spontaneous detorsion 1, 2
• Clinical presentations overlap significantly between different etiologies; maintain high suspicion and consult urology when in doubt 2
• Power Doppler is essential in prepubertal boys who normally have reduced intratesticular blood flow 3, 1
• Never delay surgical exploration for imaging when clinical suspicion for torsion is high, as the 6-8 hour window is critical for testicular salvage 1, 2