Whirlpool Sign on Doppler Ultrasound
The whirlpool sign is the most specific ultrasound finding for testicular torsion, representing the twisted spermatic cord visualized as a spiral or target-like structure with multiple concentric rings, and should prompt immediate urological consultation for surgical exploration. 1
Diagnostic Significance
The whirlpool sign demonstrates the actual anatomical twist of the spermatic cord and can be identified on both grayscale and color Doppler imaging 1:
On grayscale ultrasound: The twisted spermatic cord appears as a target-like structure with multiple concentric rings, representing the spiraled vessels and ductus deferens rather than their normal linear tubular appearance 2
On color Doppler: The sign manifests as a characteristic spiral pattern of blood vessels, creating the distinctive "whirlpool" appearance 1, 2
Sensitivity: The whirlpool sign has 96% sensitivity for detecting testicular torsion when properly identified 1
Clinical Application
Imaging Protocol
The spermatic cord should be systematically examined from the outer inguinal ring to the upper pole of the testis to identify the whirlpool sign 2:
Use high-resolution linear transducers (>10 MHz) with optimized Doppler settings including low pulse repetition frequency (<4 cm/s) and low wall filter (<100 Hz) 2
Compare findings to the contralateral normal testis as an internal control 1
Power Doppler may be more sensitive for detecting low-flow states, particularly in prepubertal boys 1, 3
Guiding Manual Detorsion
The whirlpool sign serves a critical therapeutic role by identifying the direction of torsion before attempting manual detorsion 3:
Visualizing the spiral direction helps determine whether to rotate the testis medially or laterally (most commonly, the "open book" lateral rotation is needed) 3
Color Doppler should be performed immediately after each rotation attempt to document restoration of arterial flow 3
Ultrasound-guided manual detorsion is non-invasive, quick, and can rapidly restore testicular blood flow, maximizing testicular salvage rates 4, 5
Critical Pitfalls
False-Negative Considerations
The absence of a whirlpool sign does not exclude testicular torsion 1:
Partial torsion (<360 degrees) may not produce a visible whirlpool sign but still requires surgical intervention 1
Early presentation or spontaneous detorsion can result in normal-appearing anatomy despite clinical torsion 1
When clinical suspicion remains high despite absent whirlpool sign, immediate surgical exploration should proceed, as testicular viability is compromised after 6-8 hours of ischemia 1, 3
Technical Limitations
Color Doppler ultrasound has variable sensitivity (69-96.8%) for testicular torsion, with false-negative evaluations occurring in up to 30% of cases 1:
Complete torsion (>450 degrees) shows straightforward absent flow, but partial torsion presents the greatest diagnostic challenge 1
Prepubertal boys normally have reduced intratesticular blood flow, which can lead to false-positive interpretations 1
Time-Critical Management
Regardless of imaging findings, surgical exploration and detorsion must occur within 6-8 hours of symptom onset to prevent permanent ischemic damage and testicular loss 1, 3:
The whirlpool sign confirms the diagnosis but should never delay surgical intervention when clinical suspicion is high 1
Successful identification of the whirlpool sign allows for ultrasound-guided manual detorsion attempts, which can convert an emergency surgery to a semi-elective procedure if blood flow is restored 3, 4