Sonographic differential diagnosis of acute scrotum: real-time whirlpool sign, a key sign of torsion.

OBJECTIVE The purpose of this study was to prospectively investigate the role of high-resolution and color Doppler sonography in the differential diagnosis of acute scrotum and testicular torsion in particular. METHODS Patients who underwent sonography for acute scrotum between April 2000 and September 2005 were included in the study. Gray scale and color Doppler sonography of the scrotum was performed. The spermatic cord was studied on longitudinal and transverse scans from the inguinal region up to the testis, and the whirlpool sign was looked for. RESULTS During this period, 221 patients underwent sonography for acute scrotum. Sixty-five had epididymo-orchitis with a straight spermatic cord, a swollen epididymis, testis, or both, an absent focal lesion in the testis, and increased flow on color Doppler studies along with the clinical features of infection. Three had testicular abscesses. Sonography revealed features of torsion of testicular appendages in 23 patients and acute idiopathic scrotal edema in 19. Complete torsion was seen in 61 patients who had the whirlpool sign on gray scale imaging and absent flow distal to the whirlpool. There was incomplete torsion in 4 patients in whom the whirlpool sign was seen on both gray scale and color Doppler imaging. Nine patients had segmental testicular infarction, and 1 had a torsion-detorsion sequence revealing testicular hyperemia. In 14 patients, the findings were equivocal. There was a complicated hydrocele, mumps orchitis, and vasculitis of Henoch-Schönlein purpura in 1 patient each. Five patients had normal findings. Fourteen were lost for follow-up. CONCLUSIONS Sonography of acute scrotum should include study of the spermatic cord. The sonographic real-time whirlpool sign is the most specific and sensitive sign of torsion, both complete and incomplete. Intermittent testicular torsion is a challenging clinical condition with a spectrum of clinical and sonographic features.