Introduction:
Testicular ultrasound also called a testicular sonogram or scrotal ultrasound is used to look at the testicle and its surrounding soft tissue structures. The testicle is a reproductive organ in males found inside the scrotum, which measures about 4.5 to 5.1 cm. A pair of testis located inside the scrotum produces sperms and testosterone hormone. Luteinizing hormone (an anterior pituitary hormone) controls the production of testosterone, and sperm production is controlled by testosterone and the follicle-stimulating hormone (an anterior pituitary hormone). The scrotum is a bag or pouch of skin containing testicles, epididymis, appendix testis, spermatic fascia (fibrous covering of the testis), and blood vessels. The epididymis is a narrow, coiled tube connected to the testis and vas deferens at each end.
How Does Ultrasound Work?
Ultrasound is a diagnostic tool that captures the images of soft tissues inside the body using sound waves. Ultrasound imaging is also called a sonogram. During the ultrasound, a handheld probe called the transducer produces high-frequency sound waves which bounce off the organs and are received by the transducer. The transducer processes the reflected waves, which are then converted by the computer into images of the organs.
The sound waves travel fastest through bone tissue and slowest through the air. The speed of the sound waves and the amount of the sound waves returned to the transducer determine the types of tissue.
What Are the Uses of Testicular Ultrasound?
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Determine the size and symmetry of the testicles.
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Pain or swelling in the scrotum.
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Determine the echogenicity (density) of the scrotum.
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Determine the change in the blood flow to the testicle.
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Undescended testicle (a condition in which the testicle is not moved into its proper position).
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To detect testicular injury (pain, swelling of the scrotum, blood in the urine).
How Is a Testicular Ultrasound Performed?
For testicular ultrasounds, patients have to remove their clothes and wear the hospital gown provided. During the testicular ultrasound, patients are asked to lie on their backs while spreading their legs. To elevate the scrotum, the technician may keep a towel below the scrotum or place wide strips of tape across the thighs.
Then, the radiologist or diagnostic medical sonographer will apply a water-soluble gel over the scrotum. This gel may feel cool, and it does not cause any pain. The radiologist will gently move a probe called a transducer over the skin on top of the gel. This procedure requires a 12 to 17 MHz (megahertz) frequency transducer to obtain excellent details of the testicle. They move the probe back and forth to get the images clearly. Patients may need to change their body positions to look at different areas. Finally, they wipe off the gel over the scrotum. This procedure usually takes about 30 minutes to complete.
The technician may include a Doppler ultrasound to detect the details of blood flow inside the vessels supplying the testis. After the scan, the radiologist reviews the images and sends the report to the physician. Patients can follow their regular diet and regular activities after the scan.
What Are the Zones of Testicular Ultrasound?
The testicular ultrasound produces sound waves and sends them to the scrotum. The normal and abnormal tissue sends back different kinds of echoes. These echoes are processed in the computer, which translates them into a video picture of the scrotum.
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Echogenic Zones - The areas which can produce echoes.
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Isoechoic Zones - Areas of normal tissue bounce back the same amount of sound waves which they received.
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Hypoechoic Zones - Hypoechoic areas send back only fewer echoes than they received and often indicate the presence of cancer. They appear dark gray on the screen.
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Hyperechoic Zones - Hyperechoic areas send back considerably more echoes than they received, indicating the presence of calcifications or stones. They appear light gray.
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Anechoic Zones - Anechoic zones do not send back any sound waves, which indicate the fluid-filled area as in cysts. They appear as black on the screen.
What Are the Normal Interpretations of Testicular Ultrasound?
1. Testis:
- Normally, the testis is ovoid in shape and measures about 3 to 5 cm in diameter. It appears as a homogeneous (uniform) echogenic zone in ultrasound.
2. Epididymis:
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The epididymis is a comma-shaped structure located at the posterior aspect of the testis.
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The epididymal head is a round structure hanging over the superior pole of the testis. It measures about 5 to 12 mm in diameter. In testicular ultrasound, the epididymal head appears as an isoechoic or mild hyperechoic zone.
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The epididymal body measures about 2 to 4 mm in diameter and is located behind the inferior pole of the testicle.
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The epididymal tail measures about 2 to 5 mm in diameter and is located behind the inferior pole of the testis.
3. Scrotum:
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Normal skin thickness of the scrotum ranges between 2 to 8 mm.
4. Tunica Albuginea:
- Testicles and epididymis are covered by a capsule that is fibrous in nature called tunica albuginea. In testicular ultrasounds, they appear as a thin echogenic band.
5. Tunica Vaginalis:
- Tunica albuginea is covered by tunica vaginalis (remnants of processus vaginalis), which is divided into two layers. The visceral layer covers the tunica albuginea, and the parietal layer forms the inner lining of the scrotum.
6. Appendix Epididymis:
- Appendix epididymis is an extension of the testis usually attached to the epididymal head, which is visible only when the torsion (spiral twist) is present.
7. Mediastinum Testis:
- Tunica albuginea extends to the posteromedial aspect of the testis and forms the mediastinum testis containing blood vessels, nerves, and ducts. It appears as a thin echogenic zone.
8. Spermatic Cord:
- The spermatic contains arteries, venous plexus, nerves, and lymphatic vessels that appear as a hyperechogenic zone.
What Are the Abnormal Interpretations of the Testicular Ultrasound?
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A hydrocele is a fluid-filled sac inside the scrotum that causes enlargement of the scrotum. In hydrocele, the fluid is collected between the two layers of tunica vaginalis. It appears as an anechoic zone in the ultrasound.
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Varicocele is a condition in which veins within the scrotum become enlarged. It is more in the left testicle than the right due to its longer size. It appears as a hypo or anechoic zone in ultrasound.
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Testicular torsion, also called ball clapper deformity, in which the spermatic cord is twisted spirally, which results in decreased blood flow to the testis causing severe pain. When the tunica vaginalis is connected to the spermatic cord at a higher level, it causes the testicle to rotate freely inside the scrotal sac. It is more common in adult boys. In the early phase, it appears as echogenic. But in the later phase, it appears as an enlarged heterogeneous zone in ultrasound.
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Scrotal wall cellulitis is the inflammation of the scrotal wall due to infection. It is more common in immunosuppressive patients. It appears as a hypoechoic zone with the increased vascular flow on color Doppler ultrasound.
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Orchitis is the swelling of the testis due to bacterial infection. Sometimes, secondary to paramyxovirus. It appears as a hypoechoic zone in ultrasound.
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Epididymitis is the swelling of the epididymis due to bacterial infection. It can cause sudden scrotal pain. It appears as hypoechoic zones in ultrasound.
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A testicular cyst is a fluid-filled sac found in the testis. It appears as an anechoic zone in ultrasound.
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A testicular tumor (cancer) usually appears as a hypoechoic homogeneous (mixed) zone.
Conclusion:
Testicular ultrasound is a noninvasive imaging technique used to visualize testis and the surrounding structures. This procedure requires less time, and it does not cause pain to the patients. The testicular ultrasound uses a high-frequency transducer which can provide excellent details of the testicles. This scan is cost-effective and easily available. Patients do not require preparation before the scan. This scan does not produce ionizing radiation, and hence it is a relatively safe imaging technique. Testicular ultrasound is the first-line imaging technique recommended for patients with scrotal diseases.