The Scrotum and Penis



The Scrotum and Penis


Wayne C. Leonhardt

Aaron M. Chandler















High-frequency grayscale sonography with spectral, color, and power Doppler is the imaging modality of choice and the gold standard for evaluating patients with acute scrotal pain, a scrotal mass, or to assess testicular perfusion when testicular torsion is suspected.1, 2 and 3 Compared with other imaging modalities, sonography provides expedient and accurate differentiation of many causes of scrotal pain.3, 4 and 5 The diagnosis of scrotal disease is based on many factors, including a thorough clinical history, physical examination, and sonographic findings.3,6,7 When patients present with scrotal pain or abnormality, clinical evaluation alone is difficult, and the cause of the patient’s symptoms frequently remains unanswered. Sonography is used to determine whether a palpable mass is cystic or solid and differentiate between intratesticular and extratesticular abnormalities.1,3,7 The distinction between an intratesticular lesion and an extratesticular lesion is an important one considering most intratesticular solid masses are considered malignant until proven otherwise.8,9 Conversely, extratesticular masses tend to be benign regardless of their cystic or solid nature.1,8,10 High-resolution grayscale sonography has been shown to be nearly 100% accurate in its ability to characterize the intrascrotal anatomy and distinguish intratesticular and extratesticular abnormalities.3,7,14

Sonography is also useful in the follow-up examination of infection and trauma. Incidentally, 10% to 15% of testicular tumors are identified after an episode of scrotal trauma.11,12 Owing to its speed and efficacy, color Doppler sonography is the most useful imaging technique to establish the diagnosis of testicular torsion in addition to differentiating torsion from epididymo-orchitis.9,13,15 With an accuracy approaching 100%, sonography is considered the primary imaging modality to assess intratesticular arterial perfusion.13, 14, 15 and 16 Nuclear medicine and sonography are comparable in the detection of reduced or absent intratesticular flow.15

When a patient presents with an undescended testis, the evaluation begins with sonography to explore the inguinal canal. In 80% of cases, the undescended testis is located in the inguinal canal.14,15 Magnetic resonance imaging (MRI) is recommended to locate intra-abdominal testes when sonography fails to locate an undescended testis within the inguinal canal. MRI is 90% to 95% sensitive for identifying intra-abdominal testes.15


SONOGRAPHIC IMAGING TECHNIQUE

Optimal imaging of the scrotum is achieved using a high-frequency, 12 to 18 MHz, transducer with spectral, color, and power Doppler capabilities.3 In patients with severe scrotal swelling, a high-frequency curved linear-array transducer increases the field of view (FOV) and is useful for evaluating large segments of intrascrotal anatomy11 (Fig. 19-1). Extended FOV imaging is extremely helpful
when evaluating large anatomic segments with inflammatory processes and fluid collections because a wider FOV provides a greater understanding of anatomical relationships10 (Fig. 19-2).











Using high-resolution grayscale imaging with a transducer frequency greater than 10 MHz simplifies correlating a palpable mass with real-time imaging.11 High-frequency transducers have excellent spatial resolution and can resolve anatomic structures as small as 0.5 mm.7,10 Imaging techniques such as harmonics, compound imaging, and multifocal zones are essential to optimizing image quality.6 Adjusting color Doppler parameters by utilizing a low pulse repetition frequency (PRF), with a low wall filter, and a relatively high color gain output can improve the display of the intratesticular arteries.6,10,17


Technical Considerations

When evaluating patients for acute scrotal pain (torsion, inflammatory processes) immediately, perform a transverse image of both testes comparing echogenicity and arterial perfusion. Optimize the color and power Doppler settings.3



  • Obtain power, color, and spectral Doppler tracings to confirm the presence or absence of intratesticular arterial and venous flow.


  • Grayscale images are often nonspecific for evaluating testicular torsion and often appear normal when torsion is acute.16


  • Spectral Doppler findings suggestive of partial torsion include asymmetry in resistive indices with decreased diastolic flow or diastolic flow reversal.16


  • In the clinical setting of epididymo-orchitis, when focal hypoechoic areas are detected within the testis, ultrasound follow-up is recommended after antibiotic treatment is completed to confirm the diagnosis and observe resolution, so that tumor and or infarction can be ruled out.7


  • Large hydroceles, hematomas, marked scrotal edema, and epididymo-orchitis are scrotal conditions that decrease intratesticular perfusion, mimicking testicular torsion.


  • In patients presenting with acute epididymo-orchitis, spectral Doppler demonstrates decreased vascular resistance (resistive index [RI] < 0.5) compared with the normal contralateral testis and epididymis.11


  • Reversal of the spectral diastolic component of the intratesticular arterial flow in patients with acute epididymo-orchitis suggests venous infarction.18


  • Use color and power Doppler to differentiate epididymitis from an enlarged, noninflammatory epididymis status postvasectomy.


  • Because primary varicoceles may decompress when the patient is supine, perform the Valsalva maneuver or scan the patient in the upright position to increase venous blood flow.


  • Large varicoceles can extend posteriorly, lateral, and inferiorly to the testis, mimicking epididymitis.


  • The inguinal canal and abdomen are imaged when hernia, secondary varicocele, undescended testis, and or postsurgical complications are suspected.


  • Evaluate the spermatic cord to detect abnormalities such as solid masses, hematomas, abscess, torsion, hernias, and hydroceles.


  • Use a gel standoff pad to evaluate anterior and/or superficial lesions, such as those in the tunica vaginalis.


Protocol for Real-Time Sonography

Before scanning the scrotum, review previous studies and obtain a thorough clinical history, including the patient’s chief complaint, useful laboratory data, and any pertinent surgical history such as vasectomy, hernia repair, orchiopexy, and hydrocelectomy. Have the patient locate the area of pain, swelling, or palpable mass, and ask if the patient is currently being treated with antibiotics.6,10 Once the history is obtained and documented on the anatomy worksheet, explain the procedure to the patient. The scrotal exam is performed with the patient in the supine position. The scrotum is supported on a rolled towel placed between the thighs to isolate and immobilize the anatomy for scanning.6,11,16 The penis is positioned over the suprapubic region and covered with a second towel.11 Generous amounts of warm gel should be applied to the scrotal skin as a coupling.7


Procedure for Real-Time Sonography Overview

Sonographic evaluation of the scrotum begins with a side-by-side, large-FOV image including both testes using grayscale and color Doppler imaging, comparing their echogenicity and arterial perfusion3,10,14,19 (Fig. 19-3A, B). This is paramount in the setting of acute scrotal pain with suspected testicular torsion. Longitudinal images of each testis (lateral to medial, include cine-clips) are obtained. Oblique scanning planes are useful for demonstrating the intrastesticular arteries.20 In mid testes, document the intratesticular arterial and venous waveforms with color and color with spectral Doppler. Obtain transverse images (superior, mid, inferior, include cine-clips). Document a color Doppler image mid-testis. The relevant extratesticular structures (e.g., spermatic cord, epididymis) and skin thickness are evaluated in both longitudinal and transverse image planes7,10 (Figs. 19-4 and 19-5). Include the body and tail of the epididymis when scanning the middle and lower portions of the testis, in the longitudinal plane.7,11,21


Documented Longitudinal Images



  • Longitudinal midline testis grayscale: Measure the length, and anteroposterior (AP) diameter. Midline testis: assess arterial and venous flow with color and/or power Doppler and color with spectral Doppler. Obtain an RI measurement of arterial flow.


















  • Measure the AP diameter of the scrotal wall. Subsequent images should include the lateral and medial portions of the testis.


  • Longitudinal “cine-clip” of testis lateral to medial.


  • Longitudinal epididymal head grayscale: Measure the AP diameter and length.


  • Longitudinal epididymal head with color and/or power Doppler to assess vascular perfusion.


  • Longitudinal epididymal body: The normal narrow body of the epididymis lies adjacent to the posterolateral margin of the testis. Measure the AP diameter. Perform color and/or power Doppler imaging to assess vascular perfusion.


  • Longitudinal inferior testis and epididymal tail: Measure the superior to inferior diameter of the epididymal tail. Use color and/or power Doppler to assess vascular perfusion.


  • Longitudinal spermatic cord grayscale at rest and with the Valsalva maneuver and with color and/or power Doppler, to assess venous reflux and increased flow: Measure the AP diameter of the largest vein(s) on the grayscale image.



Documented Transverse Images



  • Transverse superior testis with epididymal head in grayscale and color to assess vascularity of epididymis compared with the testis.


  • Transverse mid-testis: Obtain transverse measurement in grayscale, and document with color Doppler. Subsequent images should include inferior testis and inferior testis with epididymal tail. Obtain grayscale and color Doppler to assess the vascularity of the epididymis compared with the testis.


  • Measure the AP diameter of the scrotal wall.


  • Transverse “cine-clip” testis superior to inferior.


  • Transverse spermatic cord grayscale at rest and with the Valsalva maneuver, and with color and/or power Doppler: Measure the AP diameter of the largest vein on the grayscale image.


NORMAL ANATOMY AND SONOGRAPHIC APPEARANCE

A clear understanding of normal scrotal anatomy and vascular perfusion is paramount. Without a clear concept of normal anatomy, pathologic processes may be missed or a normal variant may be mistaken for disease.

Three major structures are contained in the scrotum: the spermatic cord; the epididymis (head, body, and tail); and the testes. The scrotum is a fibromuscular sac composed of several layers of fascia and muscle, which includes the tunica dartos, external spermatic fascia, middle spermatic fascia, cremasteric muscle, internal spermatic fascia, and tunica vaginalis.2,3,8,14,19 The normal scrotal wall thickness is approximately 2 to 8 mm, depending on the state of contraction of the cremasteric muscle.2,8,14,21 The normal sonographic appearance of the scrotal wall is homogeneous, and slightly echogenic, compared with the testis7 (Fig. 19-6). The scrotum is divided into two compartments by a midline septum, the median raphe, a fibrous band of tissue that runs ventral to the undersurface of the penis and dorsal along the middle of the perineum to the anus.2,8,10,21


Spermatic Cord and Ductus (Vas) Deferens

The spermatic cords are paired and pass from the abdominal cavity through the inguinal canal down into the scrotum.19 Each spermatic cord lies above and parallel to the inguinal ligament and suspends the testis in the scrotum. The spermatic cord is composed of arteries (the testicular, cremasteric, and deferential), veins of the pampiniform plexus, nerves, lymphatics, vas deferens, and connective tissue.2,7,8,15,22






The ductus (vas) deferens are thick paired muscular ducts about 45 cm in length. Each duct runs in the spermatic cord, through the scrotum, inguinal canal, and into the abdomen. It is a major component of the male reproduction system. The ductus (vas) deferens is a continuation of the epididymis, (tail) and transports spermatozoa from the epididymis to the ejaculatory ducts. It is divided into three segments: (1) scrotal, inferior; (2) suprascrotal, mid; and (3) prepubic, superior.2

The sonographic appearance of a normal spermatic cord in the longitudinal scan is comprised of numerous hypoechoic, slightly tortuous, linear structures measuring up to 2 mm in diameter7,15,19 (Fig. 19-7A). In the transverse plane, the sonographic appearance of the normal spermatic cord comprises of numerous hypoechoic ovoid structures with echogenic borders representing vascular walls and connective tissue2,7,15 (Fig. 19-7B).

Normal veins of the pampiniform plexus measure less than 2 mm in diameter.15,21 With color Doppler, the normal spermatic cord shows minimal flow within the arteries and veins of the pampiniform plexus at rest (Fig. 19-7C, D). In a normal patient, performing the Valsalva maneuver slightly increases the venous flow7 (Fig. 19-7E, F).

The sonographic appearance of the normal ductus (vas) deferens is a linear hypoechoic structure superior to the epididymis. The cross section view shows an ovoid structure, representing a “target” or “doughnut.” The ductus (vas) deferens is noncompressible and avascular. The normal thickness (AP) of the duct measures between 1.5 and 2.7 mm. The ductus (vas) deferens in the transverse dimension measures less than 0.5 mm2 (Fig. 19-8 A, B). The scrotal, inferior portion of the ductus (vas) deferens close to the tail of the epididymis demonstrates a convoluted tortuous appearance that is hypoechoic (Fig. 19-8C).


Epididymis

The epididymides store small quantities of sperm prior to ejaculation. Additionally, they act as a conduit for sperm originating in the testis and expressed via the seminal vesicles and secrete a small portion of the seminal fluid.7,23 The epididymis is divided anatomically into the head, body, and tail.7 The head of the epididymis, the globus major, is located superolaterally to the testis and measures 10 to 12 mm in AP diameter, and 5 to 12 mm in length.2,9,19 The body of the epididymis, the corpus, lies adjacent to the posterolateral margin of the testis and measures 2 to 4 mm in AP diameter.2,14,24,25 The tail of the epididymis, or globus minor, lies on the inferolateral surface of the testis and measures 2 to 5 mm in superior to inferior diameter.2,4,14,21,24,25 The latter continues on to become the vas deferens2,7 (Fig. 19-9).

The normal sonographic appearance of the epididymal head is homogeneous and largely isoechoic to or slightly more echogenic than the testis.2,9,11,16,21,24,25 The epididymal head is best evaluated in the longitudinal scan plane appearing as a triangle-, crescent-, or teardrop-shaped structure superior to the testis2,7, 8 and 9,15,21 (Fig. 19-10A). The echogenicity of the normal body and tail is isoechoic to hypoechoic compared

with the testis.2,9,24,25 The narrow body and curved tail are smaller, more variable in position, usually posterior and inferior to the testis, and best evaluated in the longitudinal scan plane2,4,15,21,24,25 (Fig. 19-10B, C). Color flow imaging of the normal epididymis demonstrates speckled intraepididymal arterial flow7 (Fig. 19-10D).

















Postvasectomy Changes in the Epididymis

When obtaining a patient history, it is important to know whether the patient has had a vasectomy. Patients with an undiscovered history of vasectomy could be misdiagnosed owing to a potential altered sonographic appearance of the epididymis. Epididymal changes occur in 40% of vasectomy patients and include enlargement of the epididymis, inhomogeneity, spermatoceles, dilatation of the rete testis, and sperm granulomas7,8,24,25 (Fig. 19-11A-G).

Patients presenting with scrotal pain several years after vasectomy may be suspected for “postvasectomy pain syndrome,” resulting from the obstruction of the efferent epididymal duct system with concomitant ductal dilatation, interstitial fibrosis, and chronic perineural inflammation.8

The sonographic appearance of the postvasectomy epididymis may mimic epididymitis. Clinical history and the use of color Doppler imaging differentiates between the two entities.7


Testis

The primary function of the testes is the production of sperm and testosterone. Spermatogenesis takes place within the seminiferous tubules.2,23 Testosterone, secreted by the cells of Leydig, stimulates the production of sperm and is the primary sex hormone responsible for the development of male reproductive tissues and maintenance of male secondary sex characteristics.7

Embryologically, the testes develop between the posterior abdominal wall and the peritoneum. The testes begin to pass through the inguinal ring during the seventh month of gestation and lie in the scrotum by the eighth month. During testicular descent, in the inguinal region, the caudal genital ligament is continuous with a band of mesenchyme that connects the fetal testis to the developing scrotum.7,26,27 This mesenchyme band is known as the gubernaculum testis. The gubernaculum is present only during the development of the urinary and reproductive organs and attaches to the caudal end of the testis.7 This anchors the fetal testis to the inguinal region to prevent upward movement.7 In the adult, this gubernaculum testis atrophies and its remnant, the scrotal ligament, extends from the inferior pole of the testis and tail of the epididymis to the skin of the scrotal wall.7 It secures the testis, tethering it in place and limiting the degree to which the testis can move within the
scrotum.7 The scrotal ligament can be seen in the presence of a hydrocele. The sonographic appearance of the scrotal ligament is an echogenic band extending from the caudal end of the testis to the scrotal wall7 (Fig. 19-12).






As the testes descend into the scrotum, a peritoneal lining, the processus vaginalis, fuses around the testis to form the tunica vaginalis, whose communication with the peritoneal cavity obliterates after birth.7,21 The tunica vaginalis is a peritoneal sac, composed of two layers, the visceral and parietal layers, that cover and surround the testis and epididymis except for a small posterior area.7,15,21 The visceral layer is a serous membrane that produces secretions and covers the testis and epididymis.6,7,15 The parietal layer is the inner lining of the scrotal wall6,7,14,15,21 (see Fig. 19-9). The parietal layer contains lymphatics for fluid absorption.26 Both visceral and parietal layers are separated by a potential space that normally contains a few milliliters of fluid.6,10,15,21 Bowel (scrotal hernia) and large amounts of serous fluid (hydrocele) or blood (hematocele) can accumulate in the potential space.7,19 In the normal scrotum, visualizing a small amount of fluid adjacent to the head of the epididymis is common.7,12,21 This normal amount of fluid should not be misinterpreted as a hydrocele.14,21

The tunica albuginea is a fibrous sheath that covers the testis and is seen as a thin echogenic line12,16,19 (Fig. 19-13). It invaginates the posterior aspect of the testis at the hilum to become the mediastinum testis.7,9,12,16 Sonographically, the mediastinum testis is seen as an echogenic band running in a cephalocaudal orientation within the testis in the longitudinal plane5,10,15 (Fig. 19-14A). In the transverse plane, it is seen as an ovoid echogenic structure in the 3- or 9-o’clock position13 (Fig. 19-14B). The mediastinum testis functions as a supporting system for arteries, veins, lymphatics, and seminiferous tubules.9 Numerous fibrous septa extend radially from the mediastinum into the testis, dividing it into 250 to 400 pyramid-shaped compartments called lobuli testis.7,10,14,16 Each lobule contains one to three seminiferous tubules. At the apex of each lobule, the tubules join the tubuli recti, which connect the seminiferous tubules to the rete testis.10,11,14 The rete testis is a network of epithelial-lined channels embedded within the fibrous stroma of the mediastinum testis. They drain into the epididymis through 10 to 15 efferent ductules10,14,16 (see Fig. 19-9).

High-frequency sonography can identify the normal rete testis in approximately 18% of patients. Sonographically, the normal rete testis can be seen as a hypoechoic area with striations, located adjacent to or within the mediastinum testis10,14,15 (Fig. 19-15). Dilatation of the seminiferous tubules is referred to as tubular ectasia of the rete testis. This is often seen bilaterally and is associated with epididymal cysts and spermatoceles.26

The appendix testis and appendix epididymis are embryologic remnants (Fig. 19-16A). They are not routinely visualized by sonography unless a hydrocele is present. The appendix testis is an ovoid or elongated protuberance about 5 mm in length and is attached to the upper pole of the testis, in the groove between the testis and the epididymis7,10,11 (Fig. 19-16B, C). The appendix testis has been identified in 92% of testes unilaterally and 69% bilaterally in postmortem studies. The appendix epididymis

has been identified unilaterally in 34% and bilaterally in 12% in postmortem studies.10,14 The appendix epididymis is approximately the same size as the appendix testis.10,11 The shape of the appendix epididymis is more of a stalk-like structure.10,11 Appendages of the testis and epididymis are visualized sonographically as isoechoic to echogenic protuberances superior to the testis and epididymis.7,10,11,14 Occasionally, the appendix epididymis may swell or distend, forming a cyst-like structure, not to be confused with an epididymal cyst10 (Fig. 19-16D).


























The testes are bilateral, symmetrical, ovoid glands located within the scrotum. They attain their maximum size around puberty. The normal adult testis measures 3 to 5 cm in length and 2 to 3 cm in the transverse and anteroposterior diameters2,7,14, 15 and 16 (Fig. 19-17A, B). The size of both the testis and epididymis decreases with increasing age.7,9 Sonographically, a normal adult testis appears homogeneous with medium-level echoes similar to the thyroid gland, with a smooth contour.2,7,9,11,15

In infants and children, the echogenicity of the testis is hypoechoic compared with that of an adult. At birth, the testes measure 1.5 cm in length and 1.0 cm in transverse diameter. Testicular size increases to 2.0 cm in length and 1.2 cm in transverse diameter by the time the infant is 3 months old.7,15,26 During puberty, between 9 and 16 years of age, there is a significant increase in testicular echogenicity owing to the growth of seminiferous tubules.7,26


Arterial and Venous Anatomy of the Scrotum

Scrotal blood flow is supplied by the bilateral testicular, cremasteric, and deferential arteries.2,6,7,9 Testicular arteries provide the major blood supply to the testis. They arise from the anterior aspect of the aorta just below the level of the renal arteries and enter the spermatic cord at the internal inguinal ring with the other cord structures.2,7,9,10,28 In the spermatic cord, the testicular artery is joined by the deferential artery (a branch of the vesicular artery) and

the cremasteric artery (a branch of the inferior epigastric artery).2,6,9,28 The deferential artery supplies the epididymis and vas deferens.2,6,7,9,11,28 Major blood supply to the epididymis, however, is via the superior epididymal artery, a branch of the testicular artery.6,11 The cremasteric artery supplies the peritesticular tissues (Fig. 19-18A, B). Both the deferential and cremasteric arteries also contribute a variable amount of blood to the testis via anastomoses with the testicular artery.2,7,9,28











The venous drainage from the scrotum—inclusive of the mediastinum, epididymis, and scrotal wall—is via the pampiniform plexus, which empties into the testicular veins. The right testicular vein drains into the inferior vena cava whereas the left testicular vein drains into the left renal vein2,7,9,28 (Fig. 19-18C).






The anatomy of intratesticular arteries is illustrated in Figure 19-18B. At the posterior superior aspect of the testis, the testicular artery pierces the tunica albuginea to form capsular arteries that run along the periphery of the testis in a layer known as the tunica vasculosa. Capsular arteries have centripetal branches that enter the testicular parenchyma and run toward the mediastinum testis. At the mediastinum, centripetal arteries arborize into recurrent rami arteries that course away from the mediastinum testis.
In approximately 50% of normal testes, a transmediastinal arterial branch of the testicular artery enters the mediastinum and courses through the testicular parenchyma in a direction opposite to that of the centripetal arteries to supply the capsular artery. A transmediastinal vein usually accompanies the artery.5,7,9, 10 and 11,28,29 The grayscale sonographic appearance of the transmediastinal artery is a prominent hypoechoic band traversing the testis5,9 (Fig. 19-19A). With color Doppler, the transmediastinal artery is seen as a prominent arterial branch traversing the mediastinum, demonstrating flow toward the periphery of the testis to supply the capsular arteries5,7,10,38 (Fig. 19-19B). Flow in the transmediastinal artery courses in the opposite direction relative to the centripetal arteries5,6,28


Spectral and Color Doppler Sonography of the Intrascrotal Arteries

The testis has low vascular resistance similar to that found in the brain and kidney.7 The spectral waveform of the testicular artery, and its intratesticular branches, characteristically has a low-resistance, high-flow pattern, with a mean RI of 0.62 (range: 0.48 to 0.075)10,11,17,28 (Fig. 19-20A). The normal spectral waveform of the epididymal artery is similar to that of the testicular artery, which is a low-resistance, high-flow waveform, with an RI ranging from 0.46 to 0.688,10,11,15,17 (Fig. 19-20B). Cremasteric and deferential arteries have a high-resistance, low-flow pattern with a mean RI greater than 0.75.17,28 Supratesticular arteries (testicular, cremasteric, and deferential) within the spermatic cord demonstrate either low- or high-resistance flow patterns, depending on which artery is insonated7,28 (Fig. 19-20C). With color Doppler, intratesticular arterial blood flow corresponds well with the described anatomic morphology.

Intratesticular arteries are oriented in vascular planes that intersect the mediastinum.

Longitudinal oblique views of the testis best demonstrate capsular and intratesticular arteries7,28 (Fig. 19-20D).


SONOGRAPHY OF SCROTAL DISEASE

Sonography is used to evaluate the scrotum when patients present with common symptoms such as acute painful scrotum, scrotal mass, and scrotal enlargement. Scrotal pathologies by anatomic region are shown in Table 19-1.


Decrease in Size of the Testis

Decrease in the size of a testis may be a cause of infertility or an indication of a pituitary or hypothalamus gland abnormality, such as hypogonadotropic hypogonadism. Hypogonadotropic hypogonadism results from the absence of gonadal-stimulating pituitary hormones, causing underdeveloped testicles.7,26 Other causes of testicular atrophy include cryptorchidism, “missed torsion” (ischemic damage owing to compromised blood flow), postsurgical procedures (i.e., inguinal hernioplasty, varicocelectomy), epididymo-orchitis owing to severe inflammation of the spermatic cord, and trauma.15 The sonographic appearance of testicular atrophy is a small or shrunken heterogeneous testis displaying increased echogenicity owing to fibrosis. A uniform hypoechoic testis may be seen with associated concurrent ischemia.7,15


Undescended Testis

The testicles of the fetus lie in the peritoneal cavity near the inguinal canal. Most boys’ testes are descended at birth but occasionally they descend later. The unilateral absence of a testis in the scrotum is an important finding because the incidence of malignant degeneration in the undescended testis is 48 to 50 times more likely than in the normally descended testis.7,9,14 The incidence of seminoma is 2.5 to 8 times higher in patients with undescended testis than in the general population.10,14,17 The contralateral intrascrotal testis has up to a 20% increased risk of malignancy.26 An undescended testis is also associated with infertility because sperm are exposed to abnormally high temperatures within the abdomen and/or inguinal canal.8,21,26 When the undescended testis is relocated and orchiopexy is performed before the age of 2, fertility is preserved.15 Undescended testes are at increased risk for torsion and commonly associated with malignant degeneration.26 Torsion becomes more frequent after puberty because the testis is larger than its mesentery. Sixty-four percent of patients with torsion of an intra-abdominal testis are reported to have associated testicular cancer.26 Congenital inguinal hernia is also associated with undescended testis.28 Failure to close the processus vaginalis, which forms the scrotal sac, increases the chance of bowel herniating into the scrotum. Approximately, 90% of patients with undescended testes have herniated sacs.26






















Undescended testes are bilateral in about 10% of cases.15 Approximately 80% of undescended testes are located within the inguinal canal, and the remaining 20% are intra-abdominal (from the renal hilum to the inguinal canal).7,17,21,23 The incidence of undescended testis has been reported in 0.28% of adult men and its incidence at birth has been reported to be 30.3% for premature infants and 3.4% for full-term infants.7,27

The sonographic appearance of an undescended testis is an oval or elongated well-circumscribed hypoechoic homogeneous soft tissue structure, smaller than the normal descended intrascrotal testis (Fig. 19-21). Identification of the mediastinum testis helps confirm the presence of the undescended testicle.7,9,10,15,17,21 Because sonography is relatively inexpensive, delivers no ionizing radiation, and does not require sedation, it should be the initial imaging method for undescended testis, with adjunctive computed tomography or MRI when sonography cannot definitively localize the testis.26


Acute Painful Scrotum

Acute scrotal pain is a common clinical problem in both children and adults, and it often presents a diagnostic challenge for referring clinicians. Epididymitis and epididymo-orchitis are the most common causes of acute scrotal pain.1,7,9,11,14,24,28 Differentiating patients with epididymitis from those with suspected torsion is critical. Grayscale sonography combined with color, power, and spectral Doppler increases the diagnostic efficacy in distinguishing inflammatory from ischemic processes.6,12,18,32 With prompt diagnosis, conditions such as ischemic necrosis and abscess can be surgically corrected to preserve testicular viability and function.9,20,23,30






The major causes of acute scrotal pain include epididymitis, epididymo-orchitis, focal orchitis, testicular torsion, abscess, trauma, torsion of the testicular appendices, scrotal wall inflammation, and incarcerated inguinal hernia.7 With complete testicular torsion, arterial flow is occluded and only surgical restoration of blood flow can prevent loss of the testicle.19 Abscess is also a surgical emergency because drainage of an abscess can prevent loss of the testicle. Epididymitis is painful, but antibiotic treatment usually resolves the symptoms fairly rapidly.7 Left untreated, epididymitis may progress to abscess formation, testicular infarction, and necrotizing fasciitis (Fournier gangrene).7,8,10,31


Testicular Torsion

Testicular (spermatic cord) torsion represents 20% of scrotal disease in postpubertal males.7 Torsion occurs most commonly during adolescence, between 12 and 18 years of age, with a peak incidence occurring at 14 years.7,16,26 Torsion is caused by a developmental weakness of the mesenteric attachment of the spermatic cord to the testis and epididymis. This faulty development allows the testis to fall forward within the scrotum and rotate freely within the tunica vaginalis, much like a clapper inside a bell.7,9,16,26 The severity of testicular torsion ranges from 180 to 720 degrees or greater.5,9,11,14,16,32 Twisting of the spermatic cord results in venous congestion. Initially, this prevents venous drainage and progresses to arterial occlusion, scrotal edema, hemorrhage, and infarction.5,12,13,16 Sonographic detection of a spermatic cord “torsion knot” has been described as a whirlpool pattern, manifested by concentric layers with increased and decreased echogenicity at the external inguinal canal above the testis and epididymis. Visualization of the torsion knot is the most specific and sensitive sign of either complete or incomplete testicular torsion7,11,16,30 (Fig. 19-22). Pulsed Doppler should always be used in conjunction with
color or power Doppler to confirm the presence of arterial and venous flow within the testis because color Doppler can be subject to motion artifacts.13






Early diagnosis of testicular torsion is important because it requires orchiopexy, a surgical procedure, to preserve viability and function.7,9,11,16,26 When surgery is performed within 6 hours after the onset of pain, the salvage rate is between 80% and 100%, as opposed to 70% and 76% when performed within 6 to 12 hours.5,14,15 After 12 hours, the salvageability drops to 20%.6,7,14,15,26 Surgery performed after 24 hours almost never results in successful salvage of the testis and is considered a missed torsion.5,6,11,26

There are two types of testicular torsion: intravaginal and extravaginal7,9,12,15,16,30 (Fig. 19-23A, B). In the intravaginal type, the testis rotates freely within the tunica vaginalis by a long stalk of mesorchium. Intravaginal torsion is the most frequent type of testicular torsion and is seen in 80% of cases.9,11,16 Extravaginal testicular torsion occurs exclusively in newborns.7,9,11,15,16,26 This type of torsion occurs outside the tunica vaginalis when the testes and gubernacula are not fixed and are able to freely rotate.11,14,16

Clinical signs of testicular torsion include a sudden onset of pain, followed by nausea, vomiting, and a low-grade fever.32 In 50% of cases, the symptoms mimic epididymitis.26 The cremasteric reflex is usually absent, and pain cannot be relieved by elevating the scrotum.32 When the spermatic cord twists, the affected testis maintains a higher and horizontal position in the scrotum.16 After 24 to 48 hours, the pain usually disappears, generally indicating that the testicle is dead. In newborns, testicular torsion may present with only painless swelling and redness.26






Torsion can be divided into three phases: (1) acute (within 24 hours), (2) subacute (1 to 10 days), and (3) chronic (more than 10 days).13,23 Sonographic findings in testicular torsion depend on the duration and degree of spermatic cord rotation.7,11,15,16

Grayscale sonographic findings alone of testicular torsion are nonspecific. Differentiation between inflammation and ischemia requires color, power, and spectral Doppler.9,11,15,13,23,33 Within 1 to 6 hours, the affected testis maybe slightly enlarged, with normal or decreased echogenicity7,9,11,16,23,26 (Fig. 19-24A). Epididymal enlargement (Fig. 19-24B) is common and is frequently accompanied by the “torsion knot” or “whirlpool” pattern seen in the spermatic cord (see Fig. 19-22), scrotal skin thickening, and a reactive hydrocele (Fig. 19-23C).9,11,15,16,26 Because grayscale sonography findings are often normal in the early or acute phase of torsion, the absence of intratesticular arterial flow by color and power Doppler is diagnostic for ischemia4 (Fig. 19-24A).

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Dec 10, 2022 | Posted by in ULTRASONOGRAPHY | Comments Off on The Scrotum and Penis
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