Differential Diagnosis of Acute Scrotum in Childhood and Adolescence with High-Resolution Duplex Sonography.

Acute testicular pain in childhood can be caused by testicular torsion, torsion of the appendix testis, or epididymo-orchitis. Quick and reliable diagnosis is essential for determining the further course of action (surgery or conservative approach). The diagnostic tool of choice is high-resolution sonography with a linear transducer (> 10 MHz) combined with color and spectral Doppler sonography. The Doppler device settings should include a low pulse repetition frequency (< 4 cm/s), a low wall filter (< 100 Hz), and adequate gain. Comparison with the unaffected healthy testis is essential. The most important of the three diseases is torsion of the spermatic cord because it requires immediate surgical intervention and detorsion. The affected testis is enlarged and has an inhomogeneous echotexture with hypoechoic and hyperechoic areas as well as an associated hydrocele. In testicular torsion, color Doppler shows reduced or absent intratesticular vessels in comparison with the healthy contralateral testis. Spectral Doppler shows decreased flow velocities especially during diastole in intratesticular arteries and an increased resistance index. The investigation should always include imaging of the spermatic cord from the outer inguinal ring to the upper pole of the testis. In contrast to a normal finding, the vessels and the ductus deferens are not displayed as linear tubular structures but in form of a spiral twist. Ultrasound shows a target-like structure with multiple concentric rings. Color Doppler sonography shows the typical whirlpool sign. In torsion of the appendix testis, the appendix testis is enlarged in the groove between the testis and epididymis. The longitudinal diameter of the appendix testis can be greater than 5 mm. The echogenicity of the torsed appendage can vary between hypoechoic (acute torsion) and hyperechoic (prior torsion). An associated hydrocele of varying size is usually seen. Color Doppler sonography reveals a lack of perfusion of the enlarged appendix testis and increased vascularity of the testis and primarily the epididymis. Epididymo-orchitis is characterized by an enlarged epididymis and/or testis with inhomogeneous echogenicity (hypoechoic - hyperechoic). Color Doppler sonography shows increased vascularity in comparison with the unaffected testis. Spectral Doppler reveals increased diastolic flow velocities and a decreased resistance index. Idiopathic scrotal edema and an incarcerated inguinal hernia must be ruled out in the differential diagnosis.