Scrotal (or transscrotal) ultrasound is a medical ultrasound examination of the scrotum. It is used in the evaluation of testicular pain, and can help identify solid masses. Indications Although the development of new imaging modalities such as computerized tomography and magnetic resonance imaging have opened a new era for medical imaging, high-resolution sonography remains as the initial imaging modality of choice for evaluation of scrotal disease. Many of the disease processes, such as testicular torsion, epididymo-orchitis, and intratesticular tumor, produce the common symptom of pain at presentation, and differentiation of these conditions and disorders is important for determining the appropriate treatment. High-resolution ultrasound helps in better characterize some of the intrascrotal lesions, and suggest a more specific diagnosis, resulting in more appropriate treatments and avoiding unnecessary operation for some of the diseases. Imaging technique For any scrotal examination, thorough palpation of the scrotal contents and history taking should precede the sonographic examination. Patients are usually examined in the supine position with a towel draped over their thighs to support the scrotum. Warm gel should always be used because cold gel can elicit a cremasteric response resulting in thickening of the scrotal wall; hence a thorough examination is difficult to be performed. A high resolution, near-focused, linear array transducer with a frequency of 7.5 MHz or greater is often used because it provides increased resolutions of the scrotal contents. Images of both scrotum and bilateral inguinal regions are obtained in both transverse and longitudinal planes. Color Doppler and pulsed Doppler examination are subsequently performed, optimized to display low-flow velocities, to demonstrate blood flow in the testes and surrounding scrotal structures. In evaluation of acute scrotum, the asymptomatic side should be scanned first to ensure that the flow parameters are set appropriately. A transverse image including all or a portion of both testicles in the field of view is obtained to allow side-to-side comparison of their sizes, echogenicity, and vascularity. Additional views may also be obtained with the patient performing Valsalva maneuver. Anatomy The normal adult testis is an ovoid structure measuring 3 cm in anterior-posterior dimension, 2–4 cm in width, and 3–5 cm in length. The weight of each testis normally ranges from 12.5 to 19 g. Both the sizes and weights of the testes normally decrease with age. At ultrasound, the normal testis has a homogeneous, medium-level, granular echotexture. The testicle is surrounded by a dense white fibrous capsule, the