Clinical History
A 16-year-old boy presented to the emergency department with sudden onset of right scrotal pain and swelling, 3 hours earlier. He was unable to void. There was no history of previous trauma.
Imaging Findings
Scrotal ultrasound imaging (US) and colour and spectral Doppler were performed to diagnose or exclude testicular torsion.
At B-mode, a mild testicular asymmetry was identified. The right testicle was slightly larger and more hypoechogenic than the left. At the head of the right epididymis two small cysts were identified. Adjacent to the epididymis, the spermatic cord was shown, with spiral pattern – whirlpool sign.
Colour Doppler showed preserved intra-testicular blood flow on the right side, but with a lower number of colour signals compared to the left side.
Spectral Doppler analysis results were asymmetric too, with "tardus parvus flow" at the right testicle and normal rise of waveform peak at the left one. The spectral Doppler evaluation of the spermatic cord showed a high RI value.
At the left testicle, the epididymis and spermatic cord were normal.
Manual detortion was performed.
US after detortion showed a linear spermatic cord, without whirlpool sign.
Elective bilateral orchidopexy was done.
No more episodes of scrotal pain were reported after surgery.
Discussion
Acute scrotum may have many causes, such as testicular torsion (complete, incomplete and intermittent), epididymo-orchitis, torsions of testicular or epididymal appendages, acute idiopathic scrotal oedema [1, 2].
In 26% of paediatric patients, the underlying cause of acute scrotum is testicular torsion (TT) [1]. It has an estimated incidence of 3.8/100000 and a bi-modal distribution, during the first year of life and early adolescence [1].
TT can be intravaginal (most common form, secondary to the bell-clapper deformity); extravaginal (typically in neonates, involves twisting of the spermatic cord) and mesorchial (least common form, consists of twisting of an elongated mesorchium) [1].
Testicular pain and swelling may prevent physical examination. Clinical differentiation between causes of acute scrotum may be difficult [3]. Even though there are clinical signs that suggest the aetiology, they are not accurate [2].
US and colour Doppler US are the methods of choice in the differential diagnosis of acute scrotum. They aim to rule in or rule out TT, which requires emergency surgery.
The whirlpool sign is defined as an abrupt change in course of the spermatic cord with a spiral twist of the cord [1]. At US it can have the appearance of a doughnut, a target with concentric rings, a snail shell or a storm on a weather map [2]. It can be located just outside the external inguinal ring, superiorly or posteriorly to the testis [2, 3].
Below the point of spermatic cord torsion, a pseudomass can be identified. It is composed of congested epididymis, proximal vas deferens and vascular bundle. At US it appears as an oval-shaped mass with heterogeneous echotexture [1].
In complete torsion, the whirlpool sign is seen only on B-mode US with absent intra-testicular flow on colour Doppler US. In incomplete torsion, the whirlpool sign is seen in B-mode and colour Doppler US and there is flow in the vessels of the whirlpool sign, distal to it and intra-testicular [2].
The whirlpool sign is the most definitive sign of TT, as it has 100% specificity and sensibility [2]. This is true regardless of colour Doppler US findings [2, 3].
To confirm detorsion, a follow-up US should include disappearance of the whirlpool sign and normalisation of the vascularization [3].
Prompt diagnosis and surgical detorsion are mandatory. Testicular salvage rates are approximately 80-100% within 6 hours, 70% between 6 to 12 hours, 20% after 12 hours and less than 10% after 24 hours [1, 3].
Careful evaluation of the course of the spermatic cord should always be included whenever TT is suspected [3].
Differential Diagnosis List
Testicular torsion, with whirlpool sign and preserved flow, and detorsion.
Torsion-detorsion sequence
Intermittent testicular torsion
Torsion of the testicular or epididymal appendix
Epididymo-orchitis
Acute idiopathic scrotal oedema
Final Diagnosis
Testicular torsion, with whirlpool sign and preserved flow, and detorsion.
