Emergency Ultrasound > Introduction > Anatomy

Anatomy of the Testis

The testicles are oval shaped, homogeneous low level echogenic structures and measure approximately 4 x 3 x 2 cm in size. The pediatric testicle measures approximately 1 cubic centimeter and increases steadily in size from approximately 8 years until puberty when it reaches mature size. The echo texture of both testicles should be equal and homogeneous (Fig 1a, 1c). The epididymis runs along the posterior aspect of the testicle in a craniocaudal fashion as it finally reaches the lower pole where it abruptly turns cephalad becoming the ductus deferens. The epididymal head, or globus major, projects at the cranial end of the testicle and has a slightly higher echogenicity than the normal testis. It usually measures approximately 10 mm in size and is best visualized when a small hydrocele is present.


Fig 1 a. Sagittal view normal with and without Doppler


Fig 1 b. Mediastinum normal, c. Transverse view normal.

The testicle is enveloped by many layers but is adherent to tunica albuginea (Fig 2a, 2b). The mediastinum testis is an infolding this tunica albuginea and is the site of entry of vessels and ducts into the testicle. The mediastinum testis can be visualized as an echogenic linear structure coursing through the center of the testicle (Fig 1b). The tunica vaginalis is a dual lining structure containing a visceral and a parietal layer (Fig 2c) and is the site where a hydrocele accumulates. The scrotal wall is of higher echogenicity than the testicle and should not measure more than 2 mm in size.

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Fig 2 a. Outer layers,

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Fig 2 b. Inner layers,


Fig 2 c. Testis anatomy.

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