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Indication/Technique
Scrotal ultrasound is requested when pathology is suspected.
This may include:
- Palpable swellings
- Pain
- Asymmetry
- Trauma
Ultrasound is a safe and quick way to distinguish various pathologies. Pathology may vary from innocent (e.g. hydrocele) to emergency indications (testicular torsion). Patients are examined in supine position. The scrotum is evaluated transversally (fig. 1) and sagittally (fig. 2) using a transducer (= ultrasound probe).
Figure 1. Technique for scrotal ultrasound in the transversal plane.
Figure 2. Technique for scrotal ultrasound in the sagittal plane.
By moving and rotating the transducer, each part of the scrotum is assessed systematically. When the transducer is tipped, it remains in the same location and only the sound beam changes direction. This allows you to scan in the craniocaudal direction (= transversal plane) and left-right direction (= sagittal plane).
Important: location and direction of the transducer on the patient’s skin determine anterior/posterior and left/right on the image. In general, scrotal ultrasound (as other ultrasound examinations) are performed in the transversal plane (fig. 3):
- the top of the ultrasound image is the anterior side; the bottom is the posterior side.
- Left on the image is actually right and vice versa. You are looking at the body from below, as it were (as in a transversal section of a CT scan).
Click to see overlay
Figure 3. Transversal image of the right testicle.
As a general rule, in ultrasound in the sagittal plane (fig. 4):
– the top of the ultrasound image is the anterior side and the bottom is the posterior side.
– right on the image is the foot side (= caudal) and left is the head side (= cranial).
Click to see overlay
Figure 4. Sagittal image of the right testicle.
The images can be read immediately from the screen during the examination. Orientation tip when attending a live examination: the top of the image is the location where the sound waves enter the patient first. So irrespective of position and tipping, the top is always the skin side.
Ultrasound uses sound waves, which are reflected, deflected or absorbed in the body. The reflected sound waves produce the ultrasound image. The more sound waves are reflected, the more hyperechogenic (= whiter) the tissue is imaged. Reduced reflection will cause the image to be hypoechogenic, and anechogenic (= black) if reflection is absent (fig. 5).
Figure 5. Echogenicity with corresponding terms.
The speed of sound through tissue, and tissue density and structure all influence the image obtained. For instance, high-density tissue generates relatively many echo reflections (e.g. bone/calcium) and produces a hyperechogenic image. Fluid does not reflect sound waves and is therefore anechogenic (= black). Soft tissues (e.g. organs) are somewhere between hyperechogenic and anechogenic. Isoechogenic: tissue with the same echogenicity as the surrounding tissue.