What is the most likely ultrasound finding in a 22-month-old boy with acute scrotal swelling and pain, no history of chronic conditions, normal temperature, tachycardia, normal respirations, and hypotension, presenting with sudden onset of pain and swelling on the right side of the scrotum?

Testicular Torsion: Decreased Blood Flow to the Testicle

The most likely ultrasound finding in this 22-month-old boy with acute scrotal swelling and pain is decreased or absent blood flow to the testicle, consistent with testicular torsion—a surgical emergency requiring immediate urological consultation and exploration within 6-8 hours. 1

Clinical Reasoning

This presentation is classic for testicular torsion in the pediatric age group:

• Age distribution: Testicular torsion has a bimodal distribution with peaks in neonates and postpubertal boys, but can occur at any age including toddlers 1, 2
• Acute onset: The 12-hour history of sudden pain (grabbing genitals) with scrotal swelling is characteristic of torsion's abrupt presentation 1
• Pain behavior: The child stops crying when lying flat (relief with positioning) but resumes crying when sitting, suggesting severe testicular pain 1
• Absence of fever: Normal temperature (98.6°F) makes infectious epididymitis less likely 1

Key Ultrasound Finding: Decreased Blood Flow

Doppler ultrasound will demonstrate decreased or absent blood flow to the affected testicle, which is the hallmark finding of testicular torsion. 1

Specific Ultrasound Features Expected:

• Color/Power Doppler: Decreased or absent testicular blood flow compared to the contralateral side 1
• Grayscale findings: Enlarged heterogeneous testis that may appear hypoechoic, ipsilateral hydrocele, and scrotal skin thickening 1
• Whirlpool sign: Spiral twist of the spermatic cord—the most specific ultrasound sign for torsion 1, 2
• Spectral Doppler: Diminished arterial velocity, decreased or absent diastolic flow, or increased resistive index 1

Why Other Options Are Less Likely

• Fluid on the testicle (hydrocele): While hydrocele can accompany torsion, it is not the primary diagnostic finding and occurs with multiple conditions 1
• Dilation of pampiniform plexus (varicocele): This is a chronic condition, not associated with acute pain in toddlers 1
• Enlargement of epididymis with increased flow: This finding indicates epididymitis, which typically presents with gradual onset pain, fever, and abnormal urinalysis—none of which are present here 1
• Hypoxic mass: This is not standard terminology for ultrasound findings in testicular pathology 1

Critical Management Points

Surgical exploration should proceed immediately based on clinical suspicion alone—do not delay for imaging if torsion is strongly suspected. 1, 3

Time-Critical Considerations:

• 6-8 hour window: Testicular viability is compromised if not treated within 6-8 hours of symptom onset 1, 2
• Ultrasound limitations: Color Doppler has variable sensitivity (69-96.8%), and false-negative evaluations occur in up to 30% of cases, particularly with partial torsion 1
• Prepubertal pitfall: Young children normally have reduced intratesticular blood flow, which can lead to false-positive interpretations 1

Surgical Approach:

• Bilateral orchiopexy: When torsion is confirmed, the contralateral testicle should undergo fixation to prevent future asynchronous torsion 3
• Bell clapper deformity: Found in 82% of patients with torsion, this anatomic variant allows abnormal testicular mobility 1

Common Clinical Pitfalls to Avoid

• Do not rely solely on ultrasound: When clinical suspicion is high, proceed to surgical exploration even with equivocal imaging 1, 3
• Do not wait for urinalysis: Normal urinalysis does not exclude testicular torsion 1
• Do not assume epididymitis: In toddlers without fever or urinary symptoms, torsion is more likely than epididymitis 1
• Power Doppler advantage: Use Power Doppler in prepubertal boys as it is more sensitive for detecting low-flow states 1

In this 22-month-old with acute scrotal pain and swelling, immediate urological consultation for surgical exploration is warranted, as the ultrasound will most likely show decreased or absent blood flow consistent with testicular torsion. 1, 2