What could be causing a pulsating feeling under or near my scrotum, accompanied by smaller testicles?

Pulsating Feeling Near Scrotum with Smaller Testicles

You need urgent evaluation with scrotal ultrasound with Doppler to rule out testicular torsion or other vascular abnormalities, as a pulsating sensation combined with testicular size changes could indicate compromised blood flow requiring intervention within 6-8 hours to prevent permanent testicular loss. 1

Immediate Diagnostic Approach

Obtain Duplex Doppler ultrasound of the scrotum immediately as the first-line imaging study, which has 69-96.8% sensitivity and 87-100% specificity for detecting vascular abnormalities and structural pathology. 1 The ultrasound should include:

• Grayscale examination to assess testicular size, homogeneity, and identify the "whirlpool sign" of twisted spermatic cord 1
• Color/Power Doppler assessment to evaluate testicular perfusion compared to the contralateral side, as Power Doppler is more sensitive for detecting low-flow states 1
• Spectral Doppler analysis of upper, mid, and lower poles of each testicle to detect regional flow variations and assess arterial waveforms 1

Most Likely Differential Diagnoses

Testicular Torsion (Surgical Emergency)

The pulsating sensation could represent partial testicular torsion where arterial flow persists but is compromised, as venous obstruction occurs first due to thinner vessel walls and lower pressure. 1 Key features include:

• Abrupt onset of severe scrotal pain with testicular size changes 1
• Diminished arterial velocity, decreased diastolic flow, or reversed diastolic flow on spectral Doppler 1
• Requires surgical exploration within 6-8 hours of symptom onset to prevent permanent ischemic damage 1

Critical pitfall: False-negative Doppler evaluations occur in 30% or more of cases, particularly with partial torsion or early presentation, so high clinical suspicion mandates immediate urological consultation regardless of imaging findings. 1

Varicocele

A pulsating sensation is classic for varicocele, which presents as dilated veins in the spermatic cord that feel like a "bag of worms" on palpation. 2 Varicoceles can cause:

• Testicular atrophy (smaller testicles) due to chronic venous congestion and increased testicular temperature 2
• Pulsatile sensation that increases with Valsalva maneuver 2
• Does not transilluminate uniformly as varicoceles contain blood which blocks light 2

Epididymitis/Epididymo-orchitis

This is the most common cause of testicular pain in adults, characterized by gradual onset of pain with enlarged epididymis showing increased blood flow on color Doppler. 1 However, this typically causes testicular enlargement rather than smaller testicles, making it less likely in your case. 1

Segmental Testicular Infarction

Can present with wedge-shaped avascular areas on ultrasound with variable Doppler flow, potentially causing testicular atrophy over time. 1 The median age is 37-38 years. 1

Age-Specific Considerations

• If you are under 35 years old: Testicular torsion remains a significant concern despite being more common in adolescents, as it has a bimodal distribution. 1
• If you are over 35 years old: Epididymitis is overwhelmingly the most common cause of testicular pain (approximately 600,000 cases annually in the US), though testicular torsion is rare in this age group. 1

Urgent Action Required

Do not delay evaluation. Any acute scrotal symptoms with size changes must be treated as a potential surgical emergency until torsion is excluded. 1 If testicular torsion is confirmed or highly suspected, immediate urological consultation and surgical exploration are required, as testicular viability is compromised if not treated within 6-8 hours. 1

Use the contralateral asymptomatic testicle as an internal control during ultrasound evaluation to compare size and blood flow. 1