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Sonography of Scrotum and Testes.

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Anatomy The scrotum is divided by the midline raphe. Each half of the scrotum contains a spermatic cord, testis, and epididymis. The testes descend into the scrotum at approximately the 28th gestational week via the inguinal canal through the peritoneal recess, which is called the processus vaginalis. The processus vaginalis gradually closes through infancy and childhood. The testis is covered by a visceral layer of tunica vaginalis, except where in contact with epididymis, and by the tunica albuginea. The posterior surface of the tunica albuginea extends into the testis to form the mediastinum testis. This is seen as a middle echogenic line on longitudinal US of the testis The testis has lobules containing the seminiferous tubules. Testicular lobules are occasionally identified as lines radiating from the mediastinum testis

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The size and shape of the testes change with age. Testicular size is influenced by gonadal hormones. In boys, from birth to 5 months of age, the testicular volume rises to a maximum of 0.44 (0.03) cm 3. The rise in testicular volume coincides with a peak in gonadotropic hormones, so-called minipuberty, at approximately 3 to 4 months of age. After age 5 months, the testicular volume steadily declines and reaches its minimum volume at approximately 9 months of age and remains approximately the same size until puberty. The testis is rounded in newborns and gradually becomes ovoid with growth.

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The epididymis has three parts: head, body, and tail. In the normal epididymis, only the head is routinely identified. The epididymal head is located in the upper pole of the scrotum, is triangular in shape, and has the same echogenicity as the testis. Testicular appendixes are remnants of the mesonephric and paramesonephric ducts. They can be identified by US in cases of hydrocele The spermatic cord appears as an echogenic band on longitudinal images and ovoid on transverse images as it passes in the inguinal canal. Color Doppler shows the testicular artery and pampiniform venous plexus.In the inguinal canal, the normal thickness of the spermatic cord is up to 4 mm. The normal inguinal canal does not contain fluid.

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Ultrasound (US) is a readily available and relatively inexpensive imaging modality that can be performed on patients at any age without the need for sedation or any other pretest preparation. US examinations are safe and there is no significant biologic risk from radiation exposure. Different pathologies of the scrotum may have similar clinical presentation, such as acute scrotal pain or scrotal mass. US of the scrotum can better guide treatment by improving the definition of the scrotal pathology. For these reasons, US became the imaging modality of choice for evaluation of scrotal pathology, and, in most cases, US is the first and only imaging needed for evaluation of scrotal pathology.

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Color Doppler demonstrates capsular and intratesticular vessels. In prepubertal testes, it can be difficult to detect intratesticular flow, but the capsular arteries are easier to identify. It is, however. The resistive index of the intratesticular arteries changes with age from high to low resistive index

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Indications for Scrotal Ultrasound Pain: trauma, inflammation, torsion Mass: testicular, extratesticular Evaluation of a possible hernia and its contents Search for occult neoplasm in cases of retroperitoneal or mediastinal lymphadenopathy Follow-up of previous infections, tumors, lymphoma, leukemia Small testes, atrophy Location of undescended testes Infertility Precocious puberty or feminization

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The acute scrotum Acute scrotal pain is a medical urgency as 12% to 26% of boys who have it have testicular torsion. The main differential diagnosis includes testicular torsion, torsion of appendix testis, and epididymitis. It is crucial to rapidly diagnose testicular torsion because prognosis of the testis depends on the duration of torsion. [ Ischemia of the testis can be reversible in the first 6 hours. [ US is typically required when the clinical assessment is equivocal for testicular torsion. Testicular torsion typically presents as an acute, excruciating scrotal pain of short duration before a patient arrives in the emergency room. Physical examination typically reveals diffuse tenderness, abnormal high and horizontal position of the testis, and absence of the cremasteric reflex.

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Gray-scale findings of testicular torsion may be normal. Testicular gray-scale abnormalities include testicular swelling or heterogeneous or decreased testicular echotexture. Heterogeneous parenchymal echotexture usually indicates testicular nonviability. Other findings include swelling of the epididymis, hydrocele, and scrotal skin edema. Epididymal swelling is common in testicular torsion and, in a few cases, associated with increased epididymal flow. A gray-scale study should include evaluation of the spermatic cord. A coiled spermatic cord could be the only sign for testicular torsion as perfusion of the testis can be normal in partial torsion (