Approach to Scrotal Sonography

Introduction

High-frequency transducer sonography using gray-scale along with pulsed and color Doppler is the imaging modality of choice for evaluating patients presenting with scrotal pathology. Scrotal ultrasound (US) is often requested in an emergency setting in a case of acute scrotal pain. The leading differential diagnoses in such a scenario includes testicular torsion, acute epididymo-orchitis, and traumatic injury (in the setting of preceding trauma). In a nonacute setting, scrotal ultrasound is often requested for evaluation of chronic testicular pain or a palpable scrotal mass. The leading differential diagnoses in the nonacute setting when a mass is palpated includes a testicular neoplasm (benign or malignant) and extra testicular masses, including epididymal lesions and inguinal hernias.

Clinical correlation with history and symptoms is an extremely important aspect of scrotal sonography.

Ultrasound Technique for Scrotal Evaluation

Scrotal US is performed with the patient in the supine position and the scrotum supported by a towel placed between the thighs. Optimal results are obtained with a 10-14MHz high-frequency, linear-array transducer. Scanning is performed with the transducer in direct contact with the skin with copious amounts of gel; if necessary, a stand-off pad can be used for evaluation of superficial lesions.

The testes are examined in at least two planes (i.e., the longitudinal and transverse axes). The size and echogenicity of each testis and epididymis are compared with those on the opposite side. Scrotal skin thickness is evaluated for symmetricity as well as focal or diffuse edema. Color Doppler and pulsed Doppler parameters are optimized to display low-flow velocities and to demonstrate blood flow in the testes and surrounding scrotal structures. Color Doppler ultrasound should include comparison of right and left testicular spectral Doppler tracings. Power Doppler US may also be used to demonstrate intratesticular blood flow in patients with an acute scrotum, particularly if torsion is considered.

When evaluating patients presenting with an acute scrotum, the asymptomatic side should be scanned first in order to optimize gray-scale and color Doppler gain settings. This allows for comparison with the affected side (though a caveat is that testicular torsion can be a bilateral process in 2% of patients). Transverse images with portions of each testis on the same image should be acquired in gray-scale and color Doppler modes. Additional techniques, such as use of the Valsalva maneuver or upright positioning, can be used as needed for venous evaluation. Power Doppler sonography uses the integrated power of the Doppler signal to depict the presence of blood flow. Power Doppler sonography may be slightly more sensitive than standard color Doppler for detecting low-flow states and may provide essential information in the diagnosis of potential complete testicular torsion.