Abnormalities of the Male Genital Tract
Overview
Ultrasound, including Doppler imaging in all its forms, is the main diagnostic imaging tool for evaluating the scrotum. Computed tomography (CT) is used predominantly to evaluate metastatic spread of testicular or other intrascrotal tumors. Magnetic resonance imaging (MRI) has been used in the search for undescended testes that remain in an intraabdominal position. MRI, like CT, can be used to analyze metastatic spread of testicular tumor. Its uses in intraabdominal, intrapelvic, and intrascrotal imaging are evolving.1
Ultrasound Technique
Scrotal ultrasound is performed with use of a high-frequency transducer. The superficial position of testes in the normally thin-walled scrotum allows excellent imaging with a transducer of 7.5 MHz or higher. Longitudinal, transverse, and coronal views are taken of each hemiscrotum. Transverse views, with the addition of a convex array transducer (e-Fig. 126-1), allow the best side-by-side comparison of both testes and their adnexa, especially when checking for differences in size, echogenicity, and vascularity (e-Fig. 126-2).1–6
e-Figure 126-1 Normal testes.
The testes of a teenager are seen as homogeneously echogenic on ultrasound in the transverse plane. This image was obtained using a convex linear array probe that allowed imaging of most of both testes. These transducers can show both testes in their entirety in most cases and therefore are an improvement over linear array transducers (which are limited by the size of their footprint) for side-by-side comparisons of testes.
e-Figure 126-2 Normal Doppler flow in a testis.
The upper half of the image shows the normal testis, with color filling vessels with moving blood. Insonation of a point in the upper third of the testis provides a spectral pattern (in the lower half of the image) that shows a classic arterial signal with its systolic and diastolic components above the baseline and a relatively unchanging and continuous venous signal below it.
Normal Findings
The testes should be ovoid, nearly symmetric in size (Box 126-1), and homogeneously echogenic. A highly echogenic linear focus (seen posteriorly and superiorly) represents the mediastinum testis (Fig. 126-3), which is the inward extension of the tightly adherent covering of the testis, the tunica albuginea. Fibrous septa extending from the mediastinum testes divide the testes into more than 250 lobules. The spermatic cord, draining veins, lymphatics, nerves, vas deferens, and a single testicular artery run within the mediastinum testis.6–9
Figure 126-3 Mediastinum testis.
A transverse sonogram shows a linear echogenicity (arrow) within a normal testis that is the mediastinum testis.
The head of the epididymis (e-Fig. 126-4) sits atop the superior pole of each testis. The head is continuous with the epididymal body and tail, which travel inferiorly along the posterolateral margin of the testis. The echogenicity of the epididymis is normally homogeneous. It may be of equal or of slightly greater or lesser echogenicity than that of the testes.6–9
e-Figure 126-4 Normal epididymis.
In this longitudinal sonogram, cursors mark off the head of the epididymis (E), which sits atop the superior testis (T). The normal epididymal body and tail, which travel along the side of the testis, are more difficult to separate from normal testis.
The scrotal wall should be between 3 and 6 mm thick. Beneath the scrotal wall are the two layers of the tunica vaginalis (Fig. 126-5), the outer (parietal) and the inner (visceral) layers, which are the residua of the processus vaginalis (i.e., peritoneum that descended with the testis from the abdomen). The visceral layer covers the testis on its anterior border and is attached to the tunica albuginea. Between the tunica’s two layers is a potential space that normally may contain as much as 1 to 2 mL of fluid. It is here that the fluid of a hydrocele may accumulate.6–9
Figure 126-5 A schematic drawing of the scrotum and its contents as seen in the longitudinal plane through a single testis.
Note the tunica albuginea surrounding the lobules of the testes. The tunica albuginea, in turn, is surrounded by the visceral layer of the tunica vaginalis and the more superficial parietal layer of the tunica vaginalis. (From Cohen HL, Sivit C, eds. Fetal and pediatric ultrasound: a casebook approach. New York: McGraw-Hill; 2001. Reproduced with permission of McGraw-Hill Companies.)
Three small, persistent, vestigial remnants of the mesonephric and müllerian duct systems occasionally may be seen, usually only when a normal testis is surrounded by hydrocele fluid. These remnants are the appendix testis (e-Fig. 126-6) (a remnant of the müllerian duct), which is attached to the upper pole of the testis (and the most common one to potentially undergo torsion); the appendix epididymis (a remnant of the mesonephron), which is attached to the head of the epididymis; and the vas aberrans (a remnant of the mesonephron), which is attached to the epididymis at the junction of its body and tail.6–9
Cryptorchidism
Overview: By 32 weeks’ gestational age, the testes have descended into the scrotum via the inguinal canal in 93% of all male fetuses. By 6 weeks of age, only 4% of term infants have a nonpalpable testis. Of these infants, 20% have true cryptorchidism (undescended testes). Cryptorchidism is more common on the right (70%) and is bilateral in 10% to 33% of cases. Beyond the age of 1 year, the prevalence of true cryptorchidism is approximately 1%. The etiology of cryptorchidism is not clear; it may be hormonal or mechanical (e.g., lack of proper fixation of the testis or an abnormal gubernaculum), or a combination of the two.1
Imaging: Ultrasound is the initial procedure for localization of a testis that is not palpable within the scrotum (e-Fig. 126-7). The undescended testes may be smaller and hypoplastic, although usually it is of equal echogenicity compared with the normal testis. MRI with fat-suppression techniques generally is more effective than CT for intraabdominal testes. Normal testes have a homogeneous high signal on T2-weighted images.1,6,10
e-Figure 126-7 Analysis of groin for undescended testes.
Sonogram of inguinal region. Cursors mark off the borders of a normal undescended testis found in the right groin of a child. Arrows point to the mediastinum of the testis. Color Doppler imaging denoted normal flow to the testis, which appeared homogeneous and normal. Its superficial position required a high-frequency transducer (10 MHz).
Treatment: Surgical treatment for undescended testes is orchiopexy. It is performed, especially in cases of intraabdominal testes, because of the increased risk for the development of testicular neoplasia (a 10 to 40 times greater risk, with a seminoma being the most common neoplasm).11 Spontaneous descent during the first year of life may occur from an endogenous surge of luteinizing hormone, and thus surgical correction typically is delayed until 18 to 24 months.1,6,12 After orchiopexy, 53% of the testes are reported to be abnormal by either position, volume, structure, or perfusion.1,13–16
Hydrocele
Overview: A hydrocele, which is the most common scrotal mass in a child (Fig. 126-8), results from fluid accumulated within the layers of the tunica vaginalis. Several types of hydroceles are identified (Fig. 126-9). The processus vaginalis is closed in 50% to 75% of persons by the time they are born and in most of the remainder of children by the end of the first year of life. Residual fluid from testicular descent is responsible for the noncommunicating hydroceles reported in at least 15% of male fetuses beyond 28 weeks of life. If the processus fails to close, a communicating hydrocele can develop.
Figure 126-8 Hydroceles.
On transverse plane ultrasound, two normal testes are seen as small echogenic structures within a very enlarged scrotum of a young child with large hydroceles. Typically, high-frequency transducers (e.g., 7.5 MHz and greater) are used for improved near-field resolution of superficial structures such as the testes. In cases such as this one with large hydroceles, a lower-frequency transducer may be needed to better penetrate the greater distance between the anterior and posterior scrotal walls to image the testes.
Figure 126-9 Hydrocele types.
A, Congenital or intermittent hydrocele. B, Scrotal hydrocele. C, Hydrocele of the cord. D, Inguinoscrotal hydrocele. E, Abdominoscrotal hydrocele.
In a hydrocele of the cord (a funicular hydrocele), the processus vaginalis is obliterated in its proximal and distal end and the hydrocele is contained in the patent space between these two points. In an inguinoscrotal hydrocele, the processus vaginalis is obliterated only at the internal inguinal ring and the hydrocele extends cephalad from the scrotum into the inguinal canal. In an abdominoscrotal hydrocele (e-Fig. 126-10), closure of the funicular process at the internal inguinal ring also occurs and forms a dumbbell-shaped cystic mass that protrudes into the extraperitoneal space above the inguinal area.1,17
e-Figure 126-10 Abdominoscrotal hydrocele.
A, Tubular structures (arrows) are seen extending from each side of the scrotum superiorly into the abdominal cavity on a coronal T1-weighted magnetic resonance image. This child had bilateral abdominoscrotal hydroceles; the superior extent on the right is not well visualized on this image. He presented with an enlarged scrotum and palpable inguinal area masses, the size of which changed with scrotal compression. B, A longitudinal sonogram in another patient shows a right-sided tubular, fluid-filled structure extended from the scrotum (S) to above the inguinal area (arrow). (A from Cohen HL, Sivit C, eds. Fetal and pediatric ultrasound: a casebook approach. New York: McGraw-Hill; 2001. Reproduced with permission of McGraw-Hill Companies.)
In most cases, the etiology of a hydrocele found in the child or adolescent is idiopathic. Acquired hydroceles occur after scrotal trauma or as a complication of epididymitis-orchitis, testicular torsion, or intrascrotal neoplasm (reactive hydrocele). Increasing size of a hydrocele without an intrascrotal cause suggests a patent processus vaginalis and an associated inguinal hernia.1
Imaging: Scrotal ultrasound shows the cystic nature of the hydrocele as it appears to surround the normal homogeneously echogenic testes. Septations and debris may be present, particularly if the hydrocele is infected (i.e., a pyocele) or hemorrhagic (i.e., a hematocele) (e-Fig. 126-11). Echogenic debris (e.g., cholesterol crystals) often is seen in the fluid of chronic hydroceles (Fig. 126-12), along with occasional calcifications.1
Figure 126-12 Chronic hydrocele (arrowheads).
Ultrasound in the longitudinal plane. Echogenic debris-filled fluid is seen in a chronic hydrocele (H) in the scrotum of a teenager. Excellent through transmission of sound (arrows) helps indicate that the echogenic material is complicated fluid rather than solid material. T, testicle.
Testicular Torsion
Overview: Torsion may occur at any age but is seen most often in adolescent boys between 11 and 18 years of age, perhaps because of the increase in testicular growth and weight during this time. The normal testis is strongly attached to the epididymis, which in turn is applied to the posterior scrotal wall. If these attachments fail to develop properly (the “clapper-in-a-bell” phenomenon), the testis, suspended within the tunica vaginalis, may rotate and the spermatic cord undergoes torsion. A person with acute torsion experiences sudden acute scrotal pain, accompanied by nausea and vomiting. An important finding on physical examination is a change in testicular axis from the normal vertical positioning of the testis in the scrotum to a more horizontal positioning. Within hours of torsion, a reddened scrotum develops, with or without enlargement.1
Imaging: Ultrasonography is the only diagnostic tool necessary to make the diagnosis of torsion and suggest surgical exploration. The testis is normal-sized to enlarged, with normal to decreased echogenicity (Fig. 126-13). Enlargement and hypoechogenicity are thought to be due to venous congestion. The echogenicity pattern is usually homogeneous. Epididymal enlargement may be an early finding in some cases of torsion. At least 10% of cases of torsion have associated reactive hydroceles. Ultrasound performed more than 48 hours after symptomatology (e-Fig. 126-14) may show a heterogeneous or hyperechoic testis from hemorrhage or hemorrhagic necrosis.1
Figure 126-13 Testicular torsion and axis change.
A color Doppler ultrasound in the transverse plane shows color flow in the right testicle. The right testicle is oval to circular, because it has been evaluated in the transverse plane. The left testicle is elongated as if it is in longitudinal plane. This axis change is the ultrasound equivalent of the worrisome clinical finding suggestive of torsion when accompanied by a history of sudden pain. Lack of Color Doppler flow in the left testicle confirms a left testicular torsion.
e-Figure 126-14 A longitudinal Doppler sonogram of a patient with a delayed diagnosis of testicular torsion shows an enlarged testis with heterogeneous echogenicity and no color flow.
According to this teenager’s history, the testis had twisted 4 days before he sought medical care. A, Transverse view of the testes shows a hyperechoic left testicle (arrow) with absent Doppler-able flow. A normal right testicle is present. B, Echoless areas (the horizontal arrow points to one) are consistent with destroyed areas of testicular parenchyma. A few bright echoes (vertical arrows) were consistent with areas of hemorrhage.
State-of-the-art color or power Doppler imaging methods have made ultrasound the gold standard for the imaging and preoperative diagnosis of testicular torsion. Venous flow is lost before arterial flow ceases. Color flow comparison to the contralateral testis is helpful and necessary, particularly when torsion is incomplete, in which case the diagnosis may be suggested not by absence of arterial flow but by blood flow asymmetry. The spermatic cord always should be seen, and it should be straight. When torsion is present, a spiral twist or Whirlpool sign is seen. Flow may be normal or increased in a torsed testis that spontaneously detorses.20–23
Treatment: Torsion must be corrected for testicular viability. Surgery within 24 hours leads to 60% to 70% testicular salvage, but after 24 hours salvage is only 20%. Because abnormal testicular fixation is considered a bilateral phenomenon, preventive orchiopexy often is performed on the contralateral nontwisted testis.16
