What exam is used to evaluate a swollen testicle?

Ultrasound with Doppler is the Recommended Exam for Evaluating a Swollen Testicle

Ultrasound with Doppler imaging is the standard first-line examination for evaluating a swollen testicle, as it provides high sensitivity and specificity for diagnosing testicular pathology while avoiding unnecessary surgical exploration. 1

Diagnostic Approach

Primary Imaging Modality

• Ultrasound (US) Duplex Doppler of the scrotum is rated as "Usually Appropriate" by the American College of Radiology for evaluating acute scrotal conditions 1
• The examination includes both grayscale and Doppler components to assess:
  • Testicular and epididymal morphology
  • Presence of hydrocele or other fluid collections
  • Blood flow patterns
  • Spermatic cord appearance

Key Ultrasound Components

1. Grayscale Imaging:

   • Evaluates testicular echogenicity and homogeneity
   • Identifies the "whirlpool sign" in cases of testicular torsion (96% sensitivity, 99% specificity) 1
   • Detects masses, inflammation, and structural abnormalities

2. Color Doppler Assessment:

   • Critical for evaluating testicular perfusion
   • Differentiates between conditions with increased flow (epididymitis) versus decreased/absent flow (torsion)
   • Reported sensitivity of 96-100% with specificity of 84-95% for detecting torsion 1

3. Power Doppler:

   • More sensitive than color Doppler for slow flow areas
   • Particularly useful for demonstrating intratesticular flow in prepubertal testes 1

Differential Diagnosis Based on Ultrasound Findings

Testicular Torsion

• Decreased or absent blood flow on Doppler
• Heterogeneous echotexture in later stages
• "Whirlpool sign" of the twisted spermatic cord 1

Epididymitis/Epididymo-orchitis

• Enlarged, hypoechoic epididymis
• Increased blood flow on color Doppler
• Often accompanied by scrotal wall thickening and hydrocele 1, 2

Other Conditions

• Testicular appendage torsion: small avascular structure with "blue dot sign" clinically
• Acute idiopathic scrotal edema: marked scrotal wall thickening with striated appearance
• Testicular tumor: focal mass that may show increased or decreased vascularity
• Segmental testicular infarction: wedge-shaped avascular area 1

Clinical Correlation

The TWIST (Testicular Workup for Ischemia and Suspected Torsion) scoring system can help risk-stratify patients:

• Points assigned for: testicular swelling, hard testicle, absent cremasteric reflex, nausea/vomiting, and high-riding testis
• High risk (≥5 points): 92.9% positive predictive value for torsion 2
• Low and intermediate risk patients benefit most from Doppler ultrasound evaluation 1

Important Caveats

1. False Negatives Can Occur: Color Doppler may show blood flow in early or partial torsion, leading to missed diagnoses 3

2. Timing Considerations: Ultrasound should not delay surgical intervention in cases with high clinical suspicion of torsion 1

3. Expertise Dependent: Interpretation quality depends on operator experience, particularly in pediatric patients 3

4. Limitations in Low Flow States: Power Doppler may be needed to supplement standard color Doppler in cases of slow flow 1

For equivocal cases where ultrasound findings are inconclusive but clinical suspicion remains high, surgical exploration is still warranted, as timely intervention (within 6 hours) is crucial for testicular salvage in cases of torsion 4.