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Sonography of the Scrotum¹

¹ From the Department of Radiology, University Hospitals of Cleveland, Case Western Reserve University, 11100 Euclid Ave, Cleveland, OH 44106 (V.S.D.); and Department of Radiology, University of Rochester Medical Center, Rochester, NY (R.H.G., M.O., D.J.R.). Received November 1, 2000; revision requested December 22; final revision received February 13, 2002; accepted March 14. Address correspondence to V.S.D. (e-mail: dogra@uhrad.com).

	ABSTRACT

TOP ABSTRACT INTRODUCTION ANATOMY VASCULAR SUPPLY US EVALUATION SCROTAL WALL LESIONS INGUINAL AND SCROTAL SWELLING... CONDITIONS OF THE SPERMATIC... EPIDIDYMIS CONDITIONS OF THE TESTES... CONCLUSION REFERENCES

 
Ultrasonography (US) with a high-frequency (7.5–10-MHz) transducer has become the imaging modality of choice for examination of the scrotum. US examination can provide information valuable for the differential diagnosis of a variety of disease processes involving the scrotum that have similar clinical manifestations (eg, pain, swelling, or presence of mass). The pathologic condition that may be at the origin of such symptoms can vary from testicular torsion to infection to malignancy. The ability of color and power Doppler US to demonstrate testicular perfusion aids in reaching a specific diagnosis in patients with acute scrotal pain. This review covers the anatomy of the scrotum and the scanning protocol for scrotal US, as well as detailed descriptions of disease processes and their US appearances. Newly described conditions such as intratesticular varicoceles and other benign intratesticular cystic lesions are also discussed.

© RSNA, 2003

Index terms: Orchitis, 847.201, 847.202, 847.206 • Testis, abnormalities, 847.1472, 847.1477 • Testis, cysts, 847.311 • Testis, neoplasms, 847.31, 847.32 • Testis, torsion, 847.143 • Testis, undescended, 847.1477 • Testis, US, 847.12981, 847.12983, 847.12984 • Review

	INTRODUCTION

TOP ABSTRACT INTRODUCTION ANATOMY VASCULAR SUPPLY US EVALUATION SCROTAL WALL LESIONS INGUINAL AND SCROTAL SWELLING... CONDITIONS OF THE SPERMATIC... EPIDIDYMIS CONDITIONS OF THE TESTES... CONCLUSION REFERENCES

 
Ultrasonography (US) performed with a high-frequency transducer and the use of pulsed and color Doppler modes is the imaging modality of choice for evaluating acute and nonacute scrotal disease. Many of these disease processes, including testicular torsion, epididymo-orchitis, and intratesticular tumor, produce the common symptom of pain at presentation, and differentiation of these conditions and disorders is important for determining the appropriate treatment. US with a high-frequency transducer helps to better characterize intrascrotal lesions, and in many instances the findings suggest more specific diagnoses. High-frequency US in its present state can help identify certain benign intratesticular lesions, resulting in testes-sparing surgery. Familiarity with US characteristics and the examination pitfalls of scrotal US is essential for establishing the correct diagnosis and initiating treatment.

This review is organized on an organ basis and proceeds from superficial to deep structures. We review the anatomy of the scrotum and its contents, US scanning techniques, and US features of various pathologic conditions. This review is intended to bring the reader up to date with new technology and to provide insights into the US diagnosis of scrotal disorders. Newly described entities, such as intratesticular varicocele and other benign intratesticular cystic lesions, are discussed in detail.

	ANATOMY

TOP ABSTRACT INTRODUCTION ANATOMY VASCULAR SUPPLY US EVALUATION SCROTAL WALL LESIONS INGUINAL AND SCROTAL SWELLING... CONDITIONS OF THE SPERMATIC... EPIDIDYMIS CONDITIONS OF THE TESTES... CONCLUSION REFERENCES

 
The scrotum is separated by a midline septum, with each half of the scrotum containing a testis and associated structures. The scrotal wall is composed of the following structures, listed from the superficial to the deep layers: rugated skin, superficial fascia, dartos muscle, external spermatic fascia, cremasteric fascia, and internal spermatic fascia. The tunica albuginea, covered by tunica vaginalis, consists of visceral and parietal layers normally separated by a few milliliters of fluid. The layer lining the scrotal wall is termed the parietal layer, and the layer extending over the testis and epididymis is referred to as the visceral layer. The parietal and visceral layers of the tunica join at the posterolateral aspect of the testis, where the tunica attaches to the scrotal wall. The tunica vaginalis covers the testis and epididymis except for a small posterior area.

Testicular size depends on age and stage of sexual development. At birth, the testis measures approximately 1.5 cm in length and 1 cm in width. Before the age of age 12 years, testicular volume is about 1–2 cm³. Clinically, a male individual is considered to have reached puberty once the testis achieves a volume of 4 cm³. The testes are symmetric ovoid structures and measure approximately 5 x 3 x 2 cm in the postpuberal male (1).

The fibrous tunica albuginea covers the testis and contains some nonstriated smooth muscle cells concentrated mostly on the posterior aspect of the testis; its function is to transport spermatozoa toward the rete testis and into the epididymis (2). The posterior surface of the tunica albuginea projects into the interior of the testis to form the incomplete septum, the mediastinum. From the mediastinum, numerous fibrous septa extend into the testis, dividing it into 250–400 lobules, each of which consists of one to three seminiferous tubules supporting the Sertoli cells and spermatocytes that give rise to sperm. These tubules contain loose interstitial tissue that contains Leydig cells, which are responsible for testosterone secretion. The seminiferous tubules open via the tubuli recti into dilated spaces called the rete testis within the mediastinum (Fig 1). The rete testis, a network of epithelium-lined spaces embedded in the fibrous stroma of the mediastinum, drains into the epididymis through 10–15 efferent ductules. The epididymis, a tubular structure consisting of a head, body, and tail, is located superior to and is contiguous with the posterior aspect of the testis. The head of the epididymis (globus major) lies cephalad to the testis and is composed of eight to 12 efferent ducts converging into a single larger duct in the body and tail (globus minor). This single duct becomes the vas deferens and continues in the spermatic cord.

View larger version (61K): [in this window] [in a new window]   Figure 1. Diagrammatic transverse representation of the anatomy of the testis illustrates the relationships of tunica albuginea to mediastinum testis and of mediastinum testis to rete testis. The tunica vaginalis shown here is exaggerated for illustrative purposes; actually, it is a potential space.

View larger version (160K): [in this window] [in a new window]   Figure 2a. (a) Longitudinal US scan of a normal testis in a 26-year-old man shows the appendix testis (arrow) as a hypoechoic structure. The presence of hydrocele renders the appendix testis visible. (b) Longitudinal US scan of a normal epididymis in a 24-year-old man shows normal epididymis (arrow).

View larger version (160K): [in this window] [in a new window]   Figure 2b. (a) Longitudinal US scan of a normal testis in a 26-year-old man shows the appendix testis (arrow) as a hypoechoic structure. The presence of hydrocele renders the appendix testis visible. (b) Longitudinal US scan of a normal epididymis in a 24-year-old man shows normal epididymis (arrow).

	VASCULAR SUPPLY

TOP ABSTRACT INTRODUCTION ANATOMY VASCULAR SUPPLY US EVALUATION SCROTAL WALL LESIONS INGUINAL AND SCROTAL SWELLING... CONDITIONS OF THE SPERMATIC... EPIDIDYMIS CONDITIONS OF THE TESTES... CONCLUSION REFERENCES

View larger version (155K): [in this window] [in a new window]   Figure 3. Transverse US scan of the testis shows a normal transmediastinal artery (arrow) as a linear hypoechoic band. Color Doppler flow US (not shown) revealed flow through the vessel.

	US EVALUATION

TOP ABSTRACT INTRODUCTION ANATOMY VASCULAR SUPPLY US EVALUATION SCROTAL WALL LESIONS INGUINAL AND SCROTAL SWELLING... CONDITIONS OF THE SPERMATIC... EPIDIDYMIS CONDITIONS OF THE TESTES... CONCLUSION REFERENCES

 
Scanning Protocol
Scrotal US is performed with the patient in the supine position and the scrotum supported by a towel placed between the thighs. Optimal results are obtained with a 7–10-MHz high-frequency linear-array transducer. Scanning is performed most often with the transducer in direct contact with the skin, but if necessary a stand-off pad can be used for evaluation of superficial lesions.

The testes are examined in at least two planes, along the long and transverse axes. The size and echogenicity of each testis and the epididymis are compared with those on the opposite side. Scrotal skin thickness is evaluated. Color Doppler and pulsed Doppler parameters are optimized to display low-flow velocities, to demonstrate blood flow in the testes and surrounding scrotal structures. Power Doppler US may also be used to demonstrate intratesticular flow in patients with an acute scrotum. In patients being evaluated for an acute scrotum, the asymptomatic side should be scanned initially in order to set the gray-scale and color Doppler gain settings to allow comparison with the affected side. Transverse images with portions of each testis on the same image should be acquired in gray-scale and color Doppler modes. The structures within the scrotal sac are examined to detect extratesticular masses or other abnormalities. In patients with small palpable nodules, scans should include the area of clinical concern. A finger should be placed beneath the nodule and the transducer placed directly over the nodule for scanning, or a finger can be placed on the nodule and the transducer opposite to confirm imaging of the lesion. Additional techniques such as use of the Valsalva maneuver or upright positioning can be used as needed for venous evaluation.

US Anatomy
The normal scrotal wall thickness is approximately 2–8 mm, depending on the state of contraction of the cremasteric muscle (11).

Prepubertal testes are of low to medium echogenicity, whereas pubertal and postpubertal testes are of medium homogeneous echogenicity, reflecting the development of germ cell elements and tubular maturation (12). The mediastinum testis is identified as an echogenic band of variable thickness and length extending in a caudocranial direction (Fig 4). The normal rete testis can be identified at high-frequency US in 18% of patients as a hypoechoic area with a striated configuration adjacent to the mediastinum testis (as opposed to the tubular ectasia of the rete testis when it is seen as fluid-filled dilated tubular structures) (13,14). The tunica albuginea can be seen as a thin echogenic line around the testis. The space between the two leaves of the tunica vaginalis normally contains small amounts of fluid, seen as a thin echo-free rim in the area adjacent to the head of the epididymis. This normal amount of fluid should not be misinterpreted as hydrocele. The epididymis is best evaluated in a longitudinal view when the epididymal head (globus major) can be seen as a pyramidal structure 5–12 mm in maximum length lying atop the superior pole of the testis. The head of the epididymis is usually isoechoic to the testis, and its echotexture may be coarser than that of the testis (13,15). The narrow body of the epididymis (2–4 mm in diameter), when normal, is usually indistinguishable from the surrounding peritesticular tissue. The tail of the epididymis (globus minor) is approximately 2–5 mm in diameter and can be seen as a curved structure at the inferior pole of the testis, where it becomes the proximal portion of the ductus deferens.

View larger version (143K): [in this window] [in a new window]   Figure 4. Normal testis in a 24-year-old man. Mediastinum testis (arrow) is a normal finding, seen as an echogenic band running across the testis on a sagittal US scan.

Testicular perfusion can be evaluated with color Doppler, power Doppler, and spectral Doppler US. Color Doppler US can reliably demonstrate intratesticular flow (12,16,17). Power Doppler US uses the integrated power of the Doppler signal to depict the presence of blood flow. Higher power gains are more likely with power Doppler US than with standard color Doppler US, resulting in increased sensitivity for detection of blood flow. Power Doppler scanning is valuable in scrotal US because of its increased sensitivity to low-flow states and its independence from Doppler angle correction (18,19). Pulsed Doppler US is a useful method for identification of flow in the testes with use of the time-velocity spectrum to quantify blood flow (20). The spectral waveform of the intratesticular arteries characteristically has a low-resistance pattern (16), with a mean resistive index of 0.62 (range, 0.48–0.75) (12); however, this is not true for a testicular volume of less than 4 cm³, as is often found in prepubertal boys, when diastolic arterial flow may not be detectable (21). In one report, the spectral waveform in the epididymis was described as having a low-flow, high-resistance pattern (16); however, that has not been the experience of other researchers (22). The resistive index of a normal epididymis ranges from 0.46 to 0.68, and color Doppler US can demonstrate blood flow in a normal epididymis (23).

	SCROTAL WALL LESIONS

TOP ABSTRACT INTRODUCTION ANATOMY VASCULAR SUPPLY US EVALUATION SCROTAL WALL LESIONS INGUINAL AND SCROTAL SWELLING... CONDITIONS OF THE SPERMATIC... EPIDIDYMIS CONDITIONS OF THE TESTES... CONCLUSION REFERENCES

 
Noninflammatory Causes
Noninflammatory causes of scrotal wall swelling include heart failure, idiopathic lymphedema, liver failure, and lymphatic and venous obstruction. The scrotal wall appears thickened, with layers of alternating hypoechogenicity and hyperechogenicity, called the onion-ring appearance (24). Epidermoid cysts of the scrotal wall have been described.

Inflammatory Causes
Cellulitis.—Scrotal wall cellulitis is common in patients who are obese, diabetic, or immunocompromised. The US signs are an increase in scrotal wall thickness and the presence of hypoechoic areas with increased blood flow seen at color Doppler US. Scrotal wall cellulitis may lead to scrotal abscess. Such abscesses are usually well loculated, with irregular walls and low-level internal echoes.

Fournier gangrene.—Fournier gangrene is a polymicrobial necrotizing fasciitis of the scrotum that frequently extends to the lower abdominal wall. The most common pathogens isolated in patients with this syndrome are Klebsiella, Proteus, Streptococcus, Staphylococcus, Peptostreptococcus, Escherichia coli, and Clostridium perfringens (25–27). Fournier gangrene constitutes a urologic emergency for which early recognition is demanded because of its high mortality rate—reportedly as high as 75%. The diagnosis of Fournier gangrene is based primarily on clinical examination results rather than on imaging findings. When clinical findings are ambiguous, however, diagnostic imaging is useful.

Current imaging techniques for the initial evaluation for Fournier gangrene include conventional radiography, US, and computed tomography (CT) (28). Crepitus (gas in the tissue) has been reported in 18%–62% of these cases and can be detected by using US, CT, and conventional radiography. Subcutaneous gas within the scrotal wall is the US hallmark of Fournier gangrene. At US, the gas appears as numerous, discrete, hyperechoic foci with reverberation artifacts (28,29) (Fig 5). Other US findings include scrotal wall thickening, with the echotexture of the testes and epididymis remaining normal. The only other condition manifesting with gas at US examination is an inguinoscrotal hernia. This can be differentiated from Fournier gangrene by the presence of gas within the protruding bowel lumen and away from the scrotal wall. CT and conventional radiography can also aid in determining the location and cause of gas in the scrotum.

View larger version (126K): [in this window] [in a new window]   Figure 5. Surgically proved Fournier gangrene in a 38-year-old man. Longitudinal US scan of the testis (arrowhead) shows sparing of the testis in Fournier gangrene. Both sonograms show scrotal wall thickening (open arrows) and air (long arrow) parallel to the transducer face, with reverberation artifacts (short solid arrows).

	INGUINAL AND SCROTAL SWELLING

TOP ABSTRACT INTRODUCTION ANATOMY VASCULAR SUPPLY US EVALUATION SCROTAL WALL LESIONS INGUINAL AND SCROTAL SWELLING... CONDITIONS OF THE SPERMATIC... EPIDIDYMIS CONDITIONS OF THE TESTES... CONCLUSION REFERENCES

 
Inguinal Hernia
Clinical history and physical examination results are usually sufficient to enable diagnosis of an intrascrotal inguinal hernia. US is helpful in patients with equivocal physical findings and in those presenting with acute inguinoscrotal swelling. Hernias are classified as direct or indirect, depending on their relationship to the inferior epigastric artery. Korenkov et al (33) were able to demonstrate the inferior epigastric artery in 100% of their cases of small inguinal hernia by using color Doppler US. The hernial sac most commonly contains bowel, while its next most common contents are omentum. Rare contents include other abdominal organs, such as Meckel diverticulum, urinary bladder, and others. Gray-scale US findings include a fluid- or air-filled loop of bowel in the scrotum. The presence of real-time peristalsis is diagnostic for the presence of bowel. Occasionally, because contraction of the dartos can also mimic peristalsis at real-time US, the examiner should be aware of this possibility to prevent misdiagnosis. If the omentum has herniated, hyperechoic areas are present and correspond to omental fat.

Bowel strangulation is more common in indirect than in direct inguinal hernia. An akinetic dilated loop of bowel observed at US in the hernial sac is reported (34) to have high sensitivity (90%) and specificity (93%) for the recognition of bowel strangulation. Hyperemia of scrotal soft tissue and bowel wall are suggestive of strangulation (12). Patients with Richter hernia, a strangulated hernia in which only a portion of the circumference of the bowel is obstructed (35), usually present with gastroenteritis. Such cases can pose a diagnostic challenge because of the small size of the hernia and the eccentric bowel wall involvement with limited luminal compromise. This hernia commonly occurs at a femoral site. It is important to recognize this condition because preoperative delays in diagnosis and high postoperative morbidity are very common compared with those associated with other types of strangulated hernias (36).

Hydrocele, Hematocele, and Pyocele
The normal scrotum contains a few milliliters of serous fluid between the layers of the tunica vaginalis. Approximately 85% of asymptomatic men in a series of 40 volunteers who underwent scrotal US had minimal amounts of fluid in one hemiscrotum but no hydrocele (37). A hydrocele is an abnormally large collection of serous fluid and is the most common cause of painless scrotal swelling (38). A hydrocele may develop for a variety of reasons, including trauma, infection, testicular torsion, or tumor, or it may be idiopathic. Congenital hydroceles result from a patent processus vaginalis that permits entry of peritoneal fluid into the scrotal sac. In adults, hydroceles are usually associated with an intrascrotal pathologic condition, which should be determined and treated. Hydroceles are anechoic fluid collections with good sound transmission; they surround the anterolateral aspects of the testis. Hydroceles may occasionally manifest low-level echoes secondary to high protein or cholesterol content (39,40).

Hematoceles and pyoceles are rare. A hematocele is usually secondary to trauma, surgery, or neoplasm. A pyocele results from untreated epididymo-orchitis or rupture of an intratesticular abscess into the space between the layers of the tunica vaginalis. Both conditions appear at US as complex cystic lesions with internal septations and loculations. Skin thickening and calcifications can be seen in chronic cases.

	CONDITIONS OF THE SPERMATIC CORD

TOP ABSTRACT INTRODUCTION ANATOMY VASCULAR SUPPLY US EVALUATION SCROTAL WALL LESIONS INGUINAL AND SCROTAL SWELLING... CONDITIONS OF THE SPERMATIC... EPIDIDYMIS CONDITIONS OF THE TESTES... CONCLUSION REFERENCES

 
Varicocele
Varicoceles (idiopathic or primary) are present in approximately 15% of adult men (41). Patients with idiopathic varicoceles usually present between the ages of 15 and 25 years. A varicocele is an abnormal dilatation of the veins of the spermatic cord and is usually caused by incompetent valves in the internal spermatic vein. This results in impaired drainage of blood into the spermatic cord veins when the patient assumes an upright position or during a Valsalva maneuver (42). The veins of the pampiniform plexus normally range from 0.5 to 1.5 mm in diameter, with the main draining vein being as large as 2 mm in diameter. Varicoceles are more common on the left side for the following reasons: (a) The left testicular vein is longer; (b) the left testicular vein enters the left renal vein at a right angle; (c) the left testicular artery in some men arches over the left renal vein, thereby compressing it; and (d) the descending colon distended with feces may compress the left testicular vein (43).

Palpation reveals a scrotal mass that may feel like a bag of worms, with or without a palpable thrill. In one study, all patients with palpable varicoceles had a spermatic vein diameter of 5–6 mm (44). Approximately one-third of men undergoing evaluation for infertility present with varicocele; however, not all patients with infertility have a palpable varicocele. In a study of 1,372 infertile men (45), varicocele was found at US in 29% of patients; of these, only 60% had a palpable varicocele. Diagnosis of palpable varicocele is important, because treatment improves sperm quality in as many as 53% of the cases. The relationship between nonpalpable (subclinical) varicocele and infertility remains controversial.

US should be performed with the patient in both a supine and a standing position. The US appearance of varicocele consists of multiple, hypoechoic, serpiginous, tubular structures of varying sizes larger than 2 mm in diameter that are usually best visualized superior and/ or lateral to the testis. When large, a varicocele can extend posteriorly and inferiorly to the testis. Occasionally, low-level internal echoes can be detected in these dilated veins, secondary to slow flow. Color flow and duplex Doppler US optimized for low-flow velocities help confirm the venous flow pattern, with phasic variation and retrograde filling during a Valsalva maneuver. The sensitivity and specificity of varicocele detection approaches 100% with color Doppler US.

Secondary varicoceles result from increased pressure on the spermatic vein produced by disease processes such as hydronephrosis, cirrhosis, or abdominal neoplasm (Fig 6). Neoplasm is the most likely cause of nondecompressible varicocele in men over 40 years of age; it is classically caused by a left renal malignancy invading the renal vein (15). Noncompressible varicoceles on the left or right should prompt evaluation of the retroperitoneum to exclude retroperitoneal mass and of the left renal vein for thrombus or tumor extension.

View larger version (157K): [in this window] [in a new window]   Figure 6a. Surgically confirmed secondary left varicocele in a 60-year-old man. (a) Contrast material-enhanced transverse CT scan and (b) transverse US scan of the left testis (t) reveal large left renal cell carcinoma invading the left renal vein (arrow in a), resulting in secondary varicocele (arrow in b). (Image courtesy of Patrick Fultz, MD, Rochester, NY.)

View larger version (120K): [in this window] [in a new window]   Figure 6b. Surgically confirmed secondary left varicocele in a 60-year-old man. (a) Contrast material-enhanced transverse CT scan and (b) transverse US scan of the left testis (t) reveal large left renal cell carcinoma invading the left renal vein (arrow in a), resulting in secondary varicocele (arrow in b). (Image courtesy of Patrick Fultz, MD, Rochester, NY.)

	EPIDIDYMIS

TOP ABSTRACT INTRODUCTION ANATOMY VASCULAR SUPPLY US EVALUATION SCROTAL WALL LESIONS INGUINAL AND SCROTAL SWELLING... CONDITIONS OF THE SPERMATIC... EPIDIDYMIS CONDITIONS OF THE TESTES... CONCLUSION REFERENCES

 
Epididymo-orchitis
Epididymo-orchitis and epididymitis are common causes of acute scrotal pain in adolescent boys and adults. At physical examination early in the course of the disease, the epididymis can be palpated as an enlarged tender structure separate from the testis. Clinically, scrotal pain associated with epididymitis is usually relieved when the testes are elevated over the symphysis pubis (the Prehn sign) (48). This sign may help clinically differentiate between epididymitis and torsion of the spermatic cord, in which scrotal pain is not lessened with this maneuver. In adolescents, many instances are secondary to sexually transmitted organisms such as Chlamydia trachomatis and Neisseria gonorrhoeae. In prepubertal boys and in men over 35 years of age, the disease is most frequently caused by E coli and Proteus mirabilis (49). US evaluation in patients with scrotal trauma may show epididymal enlargement and hyperemia, which should not be confused with infectious epididymitis (50). Rare causes such as sarcoidosis (51), brucellosis (52), tuberculosis, cryptococcus, and mumps may also cause epididymitis and orchitis. Drugs such as amiodarone hydrochloride may also cause epididymitis (chemical epididymitis) (2). Complications of acute epididymitis include chronic pain, infarction, abscess, gangrene, infertility, atrophy, and pyocele.

Gray-scale US findings of acute epididymitis include an enlarged hypoechoic or hyperechoic (presumably secondary to hemorrhage) epididymis (12). Indirect signs of inflammation, such as reactive hydrocele or pyocele with scrotal wall thickening, are present in most cases. The epididymis is the organ primarily involved in epididymo-orchitis, with orchitis developing in 20%–40% of cases due to direct spread of infection. Diffuse testicular involvement is confirmed by the presence of testicular enlargement and an inhomogeneous testicular echotexture. Gray-scale US findings are nonspecific, but acute epididymo-orchitis is the most common disorder with this combination of findings. Farriol et al (53) reported 11 of 20 cases with enlargement and heterogeneous echogenicity of the epididymis, testes, or both in inflammatory scrotal diseases. Orchitis is characterized by edema of the testes contained within a rigid tunica albuginea, resulting in heterogeneous echogenicity (54). The process may be seen as diffuse or focal, with the latter manifesting as multiple hypoechoic lesions within the testicular parenchyma.

Heterogeneous echogenicity does not always indicate orchitis. Leukemia and lymphoma of the testis have a similar appearance and are often (but not always) bilateral, whereas infection (excluding mumps) is usually unilateral. It is difficult to differentiate focal areas of heterogeneous echogenicity from neoplastic lesions solely on the basis of gray-scale US findings. Because this pattern is not pathognomonic of orchitis when the testes show heterogeneous echogenicity, the condition should be followed to complete resolution and documented with US to rule out tumor, infarction, and metastasis (Fig 7).

View larger version (110K): [in this window] [in a new window]   Figure 7. Clinically proved acute epididymo-orchitis in a 32-year-old man. Transverse US scan of testis shows acute epididymo-orchitis as focal areas of decreased echogenicity (arrowhead) in testicular parenchyma (T), resembling a metastatic lesion with reactive hydrocele (F). These hypoechoic areas were completely resolved at follow-up US after 2 weeks of antibiotic treatment.

View larger version (96K): [in this window] [in a new window]   Figure 8. Clinically proved acute epididymitis in a 21-year-old man. Left: Transverse US scan of right testis and epididymis shows an enlarged hypoechoic epididymis (arrow). Right: Transverse color Doppler US scan of same epididymis demonstrates increased vascularity (arrow). The testis is normal.

Sperm Granuloma
Sperm granuloma, or epididymitis nodosa, a type of chronic epididymitis, occurs secondary to inflammation, trauma, and vasectomy. Sperm granuloma, a granulomatous reaction to extravasated sperm cells, occurs after vasectomy in up to 40% of patients, but only 3% of these patients experience pain (64). At US, sperm granuloma appears as a well-demarcated hypoechoic intraepididymal lesion. Other US findings include epididymal enlargement, cystic changes, and inhomogeneous echotexture (65).

Epididymal Tumors
Spermatocele and epididymal cyst.—Extratesticular cysts are more common than intratesticular cysts. Extratesticular cysts can be found in the spermatic cord, epididymis, tunica albuginea, or tunica vaginalis. Spermatocele, a common type of extratesticular cyst, represents cystic dilatation of tubules of the efferent ductules in the head of the epididymis (11). Spermatoceles are usually unilocular but can be multilocular and may be associated with a prior vasectomy. At US examination, they are well-defined hypoechoic lesions usually measuring 1–2 cm and demonstrating posterior acoustic enhancement. They often contain low-level echogenic proteinaceous fluid and spermatozoa (66).

Epididymal cysts are less common than spermatoceles and are indistinguishable from the latter at US. Epididymal cysts contain clear serous fluid and may arise throughout the epididymis, while spermatoceles almost always arise in the epididymal head. An increased incidence of epididymal cysts has been reported in boys who are exposed in utero to diethylstilbestrol. Although epididymal head cysts cannot be differentiated from spermatoceles, they usually are not clinically relevant.

Adenomatoid tumors.—Paratesticular tumors are rare, with adenomatoid tumors constituting 30% of these tumors; they are most likely of mesothelial origin. The majority of reported cases involve the epididymis (Fig 9). Patient age at the time of presentation ranges from 18 to 79 years (47). Adenomatoid tumors are usually found incidentally by the patient or by a physician at physical examination. Characterized as a painless firm scrotal mass, an adenomatoid tumor is a benign neoplasm with no reported metastases or recurrence after excision (67). The US appearance varies from hypoechoic to hyperechoic to isoechoic, compared with adjacent tissues.

View larger version (136K): [in this window] [in a new window]   Figure 9. Surgically proved adenomatoid tumor in the left hemiscrotum of a 42-year-old man. Transverse US scan of left testis shows a heterogeneous extratesticular mass (arrow) measuring 2.75 x 2.49 cm in the inferomedial portion of the testis. At surgery, the tumor was found to arise from the tail of the epididymis.

Other rare tumors of the epididymis include leiomyoma, lipoma, rhabdomyoma, lymphoma, and lymphangioma (69). Leiomyoma of the epididymis is a rare benign neoplasm with only one-tenth the occurrence rate of rare adenomatoid tumor. Approximately 25% of solid tumors of the epididymis are malignant, and the majority are metastases from a tumor at another site. Primary adenocarcinomas of the epididymis are very rare (70). Serous papillary carcinomas have also been reported (71).

	CONDITIONS OF THE TESTES

TOP ABSTRACT INTRODUCTION ANATOMY VASCULAR SUPPLY US EVALUATION SCROTAL WALL LESIONS INGUINAL AND SCROTAL SWELLING... CONDITIONS OF THE SPERMATIC... EPIDIDYMIS CONDITIONS OF THE TESTES... CONCLUSION REFERENCES

 
Testicular Torsion
US plays an important role in helping differentiate acute epididymo-orchitis from testicular torsion, which is a surgical emergency. Both manifest with acute pain and swelling. Clinical differentiation of these conditions is difficult, with a false-positive rate of nearly 50% for diagnosis of testicular torsion based on clinical findings alone, which therefore often results in unnecessary surgical exploration (72).

In 1776, Hunter provided the first description of testicular torsion (48). The chances of torsion of the testis or its appendage developing by the age of 25 years is about one in 160 (73). Testicular torsion can occur at any age; however, it is most frequent in adolescent boys. In testicular torsion, venous obstruction occurs first, followed by obstruction of arterial flow and ultimately by testicular ischemia. The extent of testicular ischemia depends on the degree of torsion, which ranges from 180° to 720° or greater. The testicular salvage rate depends on the degree of torsion and the duration of ischemia. A nearly 100% salvage rate exists within the first 6 hours after the onset of symptoms; a 70% rate, within 6–12 hours; and a 20% rate, within 12–24 hours (74).

Two types of torsion have been described: extravaginal and intravaginal. Extravaginal testicular torsion occurs exclusively in newborns. Torsion occurs outside the tunica vaginalis when the testes and gubernacula are not fixed and are free to rotate (75). The affected neonate presents with swelling, discoloration of the scrotum on the affected side, and a firm painless mass in the scrotum (76,77). The testis is typically infarcted and necrotic at birth. US findings include an enlarged heterogeneous testis, ipsilateral hydrocele, skin thickening, and no color Doppler flow signal in the testis or spermatic cord (78). In children, power Doppler US is more sensitive than color Doppler US for detection of intratesticular blood flow. In one study (79), power Doppler US demonstrated intratesticular blood flow in 66 (97%) of 68 testes, while color Doppler US demonstrated intratesticular blood flow in 60 (88%) testes; both techniques combined depicted blood flow in all 68 (100%) testes. Color Doppler US and scintigraphy are comparable with regard to diagnosis of torsion in adolescent and adult populations (56,57). Scintigraphy remains a reasonable alternative for evaluation of acute scrotal pain and should be used when color Doppler US sensitivity for low-velocity, low-volume testicular blood flow is inadequate and the diagnosis of torsion remains in question.

Intravaginal torsion occurs within the tunica vaginalis. The predisposing factors include a long and narrow mesentery or a bell-clapper deformity, in which the tunica vaginalis completely encircles the epididymis, distal spermatic cord, and testis rather than attaches to the posterolateral aspect of the testis. The deformity leaves the testis free to swing and rotate within the tunica vaginalis much like a clapper inside a bell. The bell-clapper deformity is bilateral in most cases. A 12% prevalence of bell-clapper deformity was found in one autopsy series (80), suggesting that it is a more common deformity than intravaginal testicular torsion.

Patients with acute torsion present after a sudden onset of pain followed by nausea, vomiting, and a low-grade fever. Physical examination reveals a swollen, tender, and inflamed hemiscrotum. The cremasteric reflex is usually absent (81), and the pain cannot be relieved by elevating the scrotum (48).

US is considered the first step in evaluation. The role of color Doppler and power Doppler US in the diagnosis of acute testicular torsion is well established (17,55,57). By using the absence of identifiable intratesticular flow as the only criterion for detecting testicular torsion, color Doppler US was 86% sensitive, 100% specific, and 97% accurate in the diagnosis of torsion and ischemia in painful scrotum (56) (Fig 10). The high degree of accuracy is due to the superiority of power Doppler US depiction of intratesticular vessels, compared with that of color Doppler US, in normal prepubertal and postpubertal testes (82).

View larger version (183K): [in this window] [in a new window]   Figure 10. Surgically proved testicular torsion in a 20-year-old man. Longitudinal color Doppler US scan shows an enlarged hypoechoic testis (arrow) with no intratesticular blood flow. Increased paratesticular flow (arrowhead) is secondary to hyperemia.

Because gray-scale US findings are often normal in the early phases of torsion, the Doppler component of the examination is essential. The absence of testicular flow at color and power Doppler US is considered diagnostic of ischemia, provided that the scanner is optimized for detection of slow flow, is limited to the use of a small color-sampling box, and is adjusted for the lowest repetition frequency and the lowest possible threshold setting (86). The threshold should be set just above the level for detection of color noise.

Torsion is not an all-or-none phenomenon but may be complete, incomplete, or transient. Cases of partial or transient torsion present a diagnostic challenge. The ability of color Doppler US imaging to enable accurate diagnosis of incomplete torsion remains undetermined. The role of spectral Doppler US analysis is not well established with regard to diagnosis of partial torsion, but the findings may be useful (87). To our knowledge, there are no studies available that validate the role of spectral Doppler US in partial torsion; however, findings from sporadic case reports (88,89) exist that suggest its usefulness. Asymmetry in resistive indices, with decreased diastolic flow or diastolic flow reversal, may be seen. The presence of color or power Doppler signal in a patient with the clinical manifestation of torsion does not exclude torsion (89).

Patients with torsion of the appendix testis and appendix epididymis present with acute scrotal pain, but there are usually no other physical symptoms, and the cremasteric reflex can still be elicited. The classic finding at physical examination is a small firm nodule that is palpable on the superior aspect of the testis and exhibits bluish discoloration through the overlying skin; this is called the "blue dot" sign (90). Approximately 91%–95% of twisted testicular appendices involve the appendix testis and occur most often in boys 7–14 years old.

US evaluation of torsion of the appendages of the testes usually reveals a hyperechoic mass with a central hypoechoic area adjacent to the testis or epididymis (91–93). Reactive hydrocele and skin thickening are common in these cases. Increased peripheral flow may be seen around the twisted testicular appendage at color Doppler US (17,49,56,91). These cases are managed conservatively, with attention to pain management. The pain usually resolves in 2–3 days, with atrophy of the appendix, which may calcify. The role of US examination in torsion of testicular appendages is to exclude testicular torsion and acute epididymo-orchitis.

Primary Orchitis
Primary orchitis in isolation is rare and most commonly caused by mumps. Bilateral involvement is seen in 14%–35% of cases, and the affected testes appear enlarged with decreased echogenicity. In one study (94) of mumps-related epididymo-orchitis, nine of 11 cases were unilateral, and in all 11 cases enlarged testes and increased testicular vascularity were present. Testicular echogenicity was uniformly decreased in all 11 cases (94). Hyperemia and heterogeneity isolated to the testis can be seen in cases of orchitis, tumor, infarction, and especially in transient torsion of the testis. Because intratesticular venous flow is difficult to detect in normal testes, increased and easily detected venous flow in the testes is highly suggestive of orchitis (95).

Nonpalpable Testis
A testis may be nonpalpable because it is congenitally absent, cryptorchid, atrophic, retractile, or ectopic. Cryptorchism is defined as complete or partial failure of the intraabdominal testes to descend into the scrotal sac. The undescended testis may be positioned anywhere along the normal path of descent. The most common location is in the inguinal canal (72%), followed by prescrotal (20%) and abdominal (8%) locations (96). The undescended testis is generally smaller and less echogenic than the normal testis (Fig 11). The ectopic testis may lie in the perineum, femoral canal, superficial inguinal pouch, or contralateral hemiscrotum. The most common ectopic location is in the superficial inguinal pouch, a subcutaneous pocket in front of and lateral to the external ring (97,98).

View larger version (119K): [in this window] [in a new window]   Figure 11. Bilateral undescended testes in a 36-year-old man. Longitudinal US scan of the right testis at the level of the inguinal canal reveals an oval-shaped testis, which is hypoechoic relative to surrounding structures (arrow). Left testis is not shown.

Testicular Calcification
Testicular microlithiasis.—Testicular microlithiasis (TM) is an uncommon condition usually discovered incidentally at US. It is characterized by intratubular calcifications within a multilayered envelope containing organelles, vesicles, and collagen fibers. TM appears at US as multiple echogenic foci with no acoustic shadowing. The multilayered envelope, composed of stratified collagen fibers, is presumed to be responsible for the absence of acoustic shadowing (100,101); however, this absence could also be attributable to calcifications too small to produce shadowing. Although minor microcalcification within a testis is considered normal, the typical US appearance of TM is of multiple nonshadowing echogenic foci measuring 2–3 mm and randomly scattered throughout the testicular parenchyma (102,103) (Fig 12). The presence of five or more foci per transducer field in one testis is abnormal (15).

View larger version (151K): [in this window] [in a new window]   Figure 12. Surgically proved germ cell tumor in a 34-year-old man. Sagittal US scan of left testis shows multiple microliths (straight arrow) and a hypoechoic focal lesion (curved arrow, cursors), which was determined to be a germ cell tumor.

Macrocalcifications.—Macrocalcifications can be intra- or extratesticular. Calcifications in the epididymis can occur secondary to inflammatory conditions such as tuberculosis or trauma. Scrotoliths (scrotal pearls) are calcified bodies within the scrotum that have no clinical importance (58). They may represent a loose body caused by torsion of the appendix testis or epididymis (54). The presence of a small quantity of fluid around the testis at US examination facilitates the diagnosis of scrotoliths (Fig 13). Intratesticular macrocalcifications raise the suspicion of large cell calcifying Sertoli cell tumor, burned-out germ cell tumor, or posttraumatic change.

View larger version (146K): [in this window] [in a new window]   Figure 13. Scrotoliths (scrotal pearls) in a 30-year-old man. Transverse US scan of testes shows extratesticular echogenic foci (arrow) with posterior acoustic shadowing. There is minimal fluid in the tunica vaginalis (arrowhead).

Cysts of the tunica albuginea.—The etiology of cysts of the tunica albuginea is unknown, but these cysts are believed to be mesothelial in origin. The cysts range from 2–5 mm in size and are often detected only when a patient presents with a palpable mass (107). They can be unilocular or multilocular. They sometimes calcify, and all that remains is the palpable calcification, which casts an acoustic shadow.

Simple cysts.—Usually detected incidentally and most often occurring in men at least 40 years of age, simple cysts vary in size from 2 mm to 2 cm. These cysts are usually solitary but can also be multiple. They are located adjacent to the mediastinum testis and are associated with extratesticular spermatoceles. At US, they appear with an anechoic center and through-transmission and without a perceptible wall (108). Suspected causes of intratesticular cysts include trauma, surgery, and prior inflammation. They do not require treatment.

Epidermoid cyst.—Ranging in size from 1 to 3 cm, epidermoid cysts are uncommon benign tumors of germ cell origin and are also known as keratocysts. They are nontender and may be palpable. The patient’s age at presentation is variable but commonly ranges from 20 to 40 years (109). The US appearance of epidermoid cyst varies with the maturation, compactness, and quantity of keratin within the cyst. Four US appearances have been described: (a) a target appearance—a halo with a central area of increased echogenicity, (b) a sharply defined mass with a rim of calcification, (c) a solid mass with an echogenic rim, and (d) the classic appearance of an "onion-ring" pattern with alternating hyperechoic and hypoechoic layers (Fig 14). This onion-ring pattern is considered characteristic of an epidermoid cyst and corresponds to its natural evolution (110,111). Color flow or pulsed Doppler US examination demonstrates no blood flow within the cyst. The combination of an onion-ring configuration, negative tumor-marker status, and avascularity in the lesion help to differentiate testicular epidermoid cyst from other germ cell tumors (111). Care of these patients is based on results of total urologic evaluation followed by excisional biopsy findings that provide the final diagnosis and suggest the treatment.

View larger version (169K): [in this window] [in a new window]   Figure 14. Surgically proved intratesticular epidermoid cyst in a 21-year-old man. Longitudinal US scan of left testis reveals a well-circumscribed hypoechoic mass with a concentric lamellar pattern (curved arrow) of alternating hyper- and hypoechoic rings. This US appearance is referred to as the onion-ring appearance and is characteristic of epidermoid cyst. (Reprinted, with permission, from reference 115.)

View larger version (138K): [in this window] [in a new window]   Figure 15. Tubular ectasia in a 60-year-old man. Longitudinal US scan of the testis reveals multiple channels (arrow) on the posterolateral aspect of the testis. Color Doppler US (not shown) did not demonstrate any flow.

Intratesticular varicocele.—The pathogenesis and clinical implications of the newly defined condition intratesticular varicocele are not yet well established. An intratesticular varicocele can occur in association with an extratesticular varicocele, but intratesticular varicoceles are more commonly found alone (114). Patients with intratesticular varicocele may have pain related to passive congestion of the testis, which eventually stretches the tunica albuginea. The US appearance of an intratesticular varicocele is similar to that of an extratesticular varicocele. US features include multiple anechoic, serpiginous, tubular structures of varying sizes. Color flow and duplex Doppler US demonstrate the venous flow pattern with a characteristic venous spectral waveform that increases during a Valsalva maneuver (Fig 16) (43).

View larger version (149K): [in this window] [in a new window]   Figure 16a. Intratesticular varicocele in a 38-year-old man. (a) Transverse oblique US scan of left testis reveals multiple intratesticular anechoic cystic areas (arrowhead). (b) Duplex Doppler US scan shows that venous flow in these cystic areas increases during a Valsalva maneuver (arrowhead).

View larger version (138K): [in this window] [in a new window]   Figure 16b. Intratesticular varicocele in a 38-year-old man. (a) Transverse oblique US scan of left testis reveals multiple intratesticular anechoic cystic areas (arrowhead). (b) Duplex Doppler US scan shows that venous flow in these cystic areas increases during a Valsalva maneuver (arrowhead).

Malignant Lesions
Testicular cancer accounts for only 1% of all malignancies in men, and testicular cancer is 4.5 times more common in white men than in black men (116). In white men, it is the most common cancer in men aged 20–34 years. It was estimated that 6,900 new cases of testicular cancer will have been diagnosed in the United States in the year 2000 (117). Most testicular cancers are detected incidentally by the patient.

Patients with cryptorchism are 2.5–8 times more likely to develop testicular cancer (99). There is also an increased risk in men with Klinefelter syndrome and gonadal dysgenesis (118). Patients with testicular cancer commonly present with a painless mass or vague discomfort in the scrotum. Ten percent of patients present with acute symptoms such as fever and pain (119); 10%, following scrotal trauma (9); and 10%, with metastases (120).

It is essential to obtain a patient’s medical history in order to narrow the possible diagnoses. Most patients give accurate histories regarding the presence of pain and interval changes, duration of symptoms, and previous surgery or trauma. It is also important to know when patients have a systemic condition such as another malignancy or a hereditary or congenital disease.

The principal role of US examination in the diagnosis of testicular cancer is to help distinguish intratesticular from extratesticular lesions, because the majority of extratesticular masses are benign and intratesticular masses are more likely to be malignant (121). US does not provide the histologic and morphologic diagnosis. Gray-scale US is nearly 100% sensitive for detection of testicular tumors (119,122). There are a variety of benign intratesticular processes, such as hematoma, orchitis, abscess, infarction, and granuloma, that mimic testicular malignancy and must therefore be considered in the differential diagnosis. It is important to be familiar with their US appearance and to closely correlate US findings and patient history to avoid unnecessary interventions.

Color Doppler and power Doppler US demonstrate increased vascularity in the majority of malignant tumors and help to better define testicular involvement (123). The presence of hypervascularity is not specific enough for a diagnosis of malignancy, and it may be difficult to demonstrate increased blood flow in small tumors.

Germ Cell Tumors
Ninety to 95% of testicular tumors are derived from germ cells (124). Other malignant testicular tumors include those of gonadal stromal origin, lymphoma, leukemia, and metastases. Germ cell tumors are divided into two groups: seminomatous and nonseminomatous. This distinction determines treatment and prognosis.

Seminomatous Tumors
Seminomas are the most common type of testicular tumor and account for approximately 50% of all germ cell tumors. They occur most often in men aged in their 40s and almost never in infants (125). Seminomas are associated with the best prognosis of the germ cell tumors because of their high sensitivity to radiation and chemotherapy (99). Seminomas are also commonly found in patients with TM (126). Cryptorchism is a well-known risk factor for malignant germ cell tumor. In fact, more than 10% of such tumors are seen in patients with cryptorchism.

In a study in 54 patients with seminoma, an elevated ß–human chorionic gonadotrophic hormone level were found in 45 (83%) patients (127); in another study (121), this finding was attributed to the presence of syncytiotrophoblasts. The -fetoprotein level is never elevated in patients with pure seminoma (128,129). If histologic results suggest seminoma in the presence of an elevated -fetoprotein level, the tumor is treated as nonseminomatous.

There are three subtypes of seminomas: Typical seminomas account for 85% of the total number; anaplastic, for 5%–10%; and spermatocytic, for 4%–6%. Spermatocytic seminomas occur most often in men aged in their 60s and 70s and are associated with an excellent prognosis. On gray-scale US scans, seminoma appears as a homogeneous hypoechoic lesion, which corresponds to the smooth uniform appearance of the gross specimen (Fig 17). The entire testis is replaced by tumor in more than half the cases. In one prospective study (130), 10% of seminomas had cystic components. In a study in patients with seminoma by Hamm et al (131), histologic evaluation of the cystic areas seen on US scans corresponded to the dilated rete testis caused by tumor-related occlusion and liquefaction necrosis (Fig 18). Seminomas are usually confined by the tunica albuginea and rarely extend to peritesticular structures. Lymphatic spread to retroperitoneal lymph nodes and hematogenous metastases to lung, brain, or both are evident in about 25% of patients at the time of presentation (119).

View larger version (170K): [in this window] [in a new window]   Figure 17a. Surgically proved seminoma in a 35-year-old man. (a) Longitudinal US scan of testis reveals a well-circumscribed heterogeneous intratesticular mass. A rim of normal testicular parenchyma (arrow) surrounds the mass. (b) Color Doppler flow US scan reveals increased tumor vascularity (arrow).

View larger version (157K): [in this window] [in a new window]   Figure 17b. Surgically proved seminoma in a 35-year-old man. (a) Longitudinal US scan of testis reveals a well-circumscribed heterogeneous intratesticular mass. A rim of normal testicular parenchyma (arrow) surrounds the mass. (b) Color Doppler flow US scan reveals increased tumor vascularity (arrow).

View larger version (158K): [in this window] [in a new window]   Figure 18. Surgically proved seminoma in a 35-year-old man. Transverse oblique US scan of testis shows seminoma manifesting as cystic areas (arrowhead) with fluid-debris levels (arrow).

Embryonal carcinoma.—Embryonal carcinoma occurs most often in men aged in their 30s and is more aggressive than are seminomas. Three percent of NSGCTs are pure embryonal carcinomas; however, 45% of tumors of mixed histologic characteristics contain embryonal components. Unlike seminomas, a pure embryonal carcinoma is often small and does not cause enlargement of the scrotum. At US, embryonal carcinomas are predominantly hypoechoic lesions with poorly defined margins and an inhomogeneous echotexture (124). Echogenic foci commonly appear and represent hemorrhage, calcification, or fibrosis. Twenty percent of embryonal carcinomas and 89% of teratocarcinomas have cystic components. Tumor invasion of the tunica albuginea is common and may distort the contour of the testis (99).

Yolk sac tumor.—Yolk sac tumors are also known as endodermal sinus tumors or infantile embryonal carcinomas. These neoplasms occur most often in children younger than 5 years of age and produce -fetoprotein exclusively (125). Yolk sac elements are frequently seen in tumors with mixed histologic features in adults and thus indicate poor prognosis. The US appearance of yolk sac tumor is usually inhomogeneous and may contain echogenic foci secondary to hemorrhage.

Choriocarcinoma.—Choriocarcinoma is a highly malignant testicular tumor seen as microscopic foci in 16% of mixed germ cell tumors. Pure choriocarcinomas are rare, however, and represent only 0.3% of all testicular tumors (120). Choriocarcinomas are composed of both cytotrophoblasts and syncytiotrophoblasts, with the latter related to the elevation of human chorionic gonadotrophic hormone level. Microscopic vascular invasion is common, which explains the tendency of this tumor for early hematogenous metastasis, especially to the lungs, when the primary tumor is relatively small (121). Many choriocarcinomas show extensive hemorrhagic necrosis in the central portion of the tumor; at US, this appears as mixed cystic and solid components (132,133).

Teratoma.—Teratomas can occur in any age group. Pure teratoma is the second most common testicular tumor in prepubertal boys. In adults, pure teratoma represents 2%–3% of testicular neoplasms (121), but teratomatous components are seen in over 50% of mixed germ cell tumors. Mature teratoma in children is often benign, but teratoma in adults, regardless of age, should be treated as malignant. Teratomas are composed of all three germ cell layers—endoderm, mesoderm, and ectoderm. At US, these tumors tend to be very large and markedly inhomogeneous masses. Echogenic foci represent calcification, cartilage, immature bone, and fibrosis. Cystic components are more commonly seen in these than in other NSGCTs (120) (Fig 19).

View larger version (159K): [in this window] [in a new window]   Figure 19. Surgically proved testicular immature teratoma manifesting as a cystic mass in a 23-year-old man. Transverse US scan of right testis reveals multiple cystic areas (arrow) measuring 2-15 mm. Cystic areas involved nearly the entire testis, leaving only a rim of normal testicular parenchyma (arrowhead). These cystic changes can be easily differentiated from tubular ectasia, which is confined to the mediastinum and occurs in older men. (Reprinted, with permission, from reference 115.)

Sex Cord–Stromal Tumors
The majority of non–germ cell tumors are sex cord–stromal tumors, which represent 4% of testicular tumors. They are typically small and are usually discovered incidently. They do not have any specific US appearance but appear as well-defined hypoechoic lesions.

Leydig cell tumor.—Leydig cell tumor is the most common type of sex cord–stromal tumor of the testis; it can occur in any age group. Children often present with symptoms of precocious puberty due to production of androgens by the tumor. Adults with this tumor present with scrotal enlargement (42.5%) and gynecomastia (30%), which usually precedes testicular swelling (134). Malignant Leydig cell tumors are uncommon. These lesions are discovered in elderly men and are associated with an absence of endocrine manifestations. Recently, an association between Klinefelter syndrome and Leydig cell tumor has been suggested (135). Most patients with Klinefelter syndrome demonstrate Leydig cell hyperplasia.

Sertoli cell tumor.—Sertoli cell tumor can be one of three histologic types: Sertoli cell tumor not otherwise specified, sclerosing Sertoli cell tumor, or large cell calcifying Sertoli cell tumor (120). Although gynecomastia was described in the older literature as a frequent symptom at presentation, Young et al (136) more recently reported that only two of 60 patients with Sertoli cell tumor had gynecomastia, and these two patients also had cirrhosis.

Other sex cord–stromal tumors.—Other sex cord–stromal tumors are very rare and include granulosa cell tumor types (juvenile and adult). The juvenile type occurs in infants younger than 5 months of age and is associated with X/XY chromosome mosaicisms. Mixed germ cell–sex cord–stromal tumor—namely, gonadoblastoma—is a rare testicular tumor and is almost always seen in patients with dysgenic gonads and an intersex syndrome. Eighty percent are phenotypically female.

Lymphoma
Lymphomas constitute 5% of testicular tumors and are almost exclusively diffuse non-Hodgkin lymphoma B-cell tumors. Only 1%–3% of non-Hodgkin lymphomas involve the testes (137). In men older than 60 years, lymphoma is the most common testicular neoplasm and accounts for 50% of cases (138,139). Approximately 3% of patients with acquired immunodeficiency syndrome have non-Hodgkin lymphoma at presentation, and although testicular involvement is uncommon, case reports do exist (140,141).

Patients with testicular lymphoma commonly present with an enlarged testis and less commonly with constitutional symptoms. Asynchronous involvement of the contralateral testis is more common than in other testicular tumors and occurs in 8.5%–18% of cases (123). At gross examination, these tumors resemble seminomas and consist of a firm homogeneous tumor with or without hemorrhage and necrosis. Involvement of the spermatic cord and epididymis suggests lymphoma more than it does seminoma. Gray-scale US shows homogeneously hypoechoic testes or multifocal hypoechoic lesions of various sizes. Striated hypoechoic bands with parallel hyperechoic lines radiating peripherally from the mediastinum testis have also been described (142). Color Doppler US shows increased vascularity regardless of the size of the lesion (143).

Leukemia
Leukemic infiltration to the testis has been found at autopsy in 40%–65% of patients with acute leukemia and in 20%–35% of patients with chronic leukemia (120). In boys with acute lymphoblastic leukemia, testicular involvement is reported in 5%–10% of patients, with the majority found during clinical remission. A blood-testis barrier limiting the effect of chemotherapeutic agents in the testes explains the persistence of leukemia in the testes after remission, and this is especially true in patients with acute lymphoblastic leukemia. Any patient with a testicular mass found during the course of leukemia should undergo cytologic or histologic evaluation, because chemotherapy does not completely eliminate tumor cells from the testes. Kumar (144) reported that analysis of fine-needle aspiration specimens enabled the diagnosis of leukemic infiltration in 32 of 32 leukemia patients with bilateral or unilateral testicular enlargement whose disease was in full remission. The US appearance is similar to that of lymphoma.

Plasmacytoma
There are fewer than 50 reported cases of plasmacytoma of the testes. It has been reported (120) that, at autopsy, 2% of patients with multiple myeloma have involvement of the testes. The US appearance is of a hypoechoic mass with marked hypervascularity (145,146).

Metastases to the Testis
Testicular metastases are uncommon; in a recent study (147), only five (0.68%) such lesions were demonstrated in 738 consecutive autopsies of men with known solid malignancies. Metastases usually occur in patients with a known malignancy in an advanced stage, and the most common primary sources are prostate tumors (35%), lung tumors (19%), malignant melanoma (9%), colon tumors (9%), and kidney tumors (7%) (120).

Miscellaneous Benign and Malignant Testicular Masses
Testicular adrenal rest tissue is a benign lesion seen as an intratesticular mass in 8% of patients with congenital adrenal hyperplasia. This lesion often occur bilaterally and with a hypoechoic US appearance (133). Testicular adrenal rest tissue may be mistaken for malignancy and result in unnecessary orchiectomy.

Adenomatous hyperplasia and adenocarcinoma of the rete testis are both rare causes of scrotal enlargement (47). Their US appearances have not been well described in the literature; we are aware of only one report (148) in which the authors indicated that US findings are consistent with those of other testicular tumors.

Mesenchymal Tumors
Mesenchymal tumors of the testis, both benign and malignant, are rare and include leiomyomas, neurofibromas, adenomatoid tumors, and hemangiomas (149–152). Sarcomas include osteosarcoma, fibrosarcoma, leiomyosarcoma (153), Kaposi sarcoma, and rhabdomyosarcoma. Intratesticular adenomatoid tumors are benign neoplasms whose clinical and US features are not often reported in the literature, unlike adenomatoid tumors of the epididymis. Results in a recent report of six cases of testicular adenomatoid tumors were insufficient to establish a reliable echo pattern for diagnosis (154).

Benign Intrascrotal Fibrous Proliferation
Benign intrascrotal fibrous proliferation is characterized by a nonneoplastic mass composed of fibrous tissue. This mass affects the testis, testicular tunics, epididymis, and spermatic cord. The mass is also known as a fibrous pseudotumor and is difficult to distinguish from a malignant neoplasm, especially in the testis. The proliferation can be hyperechoic or hypoechoic at US, and there is no other specific appearance (155).

Tumorlike Lesions in the Testis
Patients with idiopathic granulomatous orchitis or testicular tumor can present with pain. Idiopathic granulomatous orchitis cannot be differentiated at US from testicular tumor. Both appear as either a focal or a diffuse mass with inhomogeneous echotexture (133,156). Idiopathic granulomatous orchitis, an inflammatory change of the testis characterized by testicular enlargement, occurs most often in middle-aged men with a history of testicular trauma. It is usually unilateral but can occur bilaterally (156). Gray-scale US demonstrates an irregular hypoechoic infiltration of the testes, with increased blood flow at the periphery of the lesion but no flow into the lesion. Idiopathic granulomatous orchitis cannot be reliably distinguished from testicular malignancies, and a final diagnosis can only be confirmed with specimens from orchiectomy (158,159).

Focal orchitis can mimic a malignant tumor. At US, orchitis appears as an ill-defined hypoechoic lesion with variable echogenicity. Color Doppler US often reveals increased vascularity.

The other entities that can mimic a tumor at US include hematoma, focal infarction, and scar tissue from prior biopsy. Hematoma appears avascular at color Doppler US. The correct diagnosis can usually be suggested by combining an accurate clinical history, tumor marker levels, and US appearance. In recent years, magnetic resonance (MR) imaging has been proposed as a problem-solving modality; however, MR imaging findings are also nonspecific and cannot help differentiate most benign and malignant testicular lesions with enough confidence to eliminate the need for biopsy (160,161). However, MR imaging is helpful in diagnosing testicular hematoma and tubular ectasia of the rete testis.

Testicular biopsy has emerged as an increasingly common procedure for the evaluation of male patients presenting with infertility. A range of US findings are encountered after testicular biopsy. The US appearance of a round hypoechoic lesion seen after biopsy can overlap that of testicular malignancy. In a patient with a focal, nonpalpable, hypoechoic, intratesticular lesion, a history of testicular biopsy should suggest to the radiologist the increased likelihood of a benign change after biopsy, in which case follow-up US should be performed (162).

Malignant Mesothelioma of Tunica Vaginalis
Plas et al (163) identified 73 cases of malignant mesothelioma of the tunica vaginalis reported during the past 30 years. More than two-thirds of these cases occurred in patients aged 45 years or older, with a median age of 60 years. A history of asbestos exposure was reported in 34.2% of the cases. US findings include hydrocele containing inhomogeneous or hypoechoic fluid or an exophytic mass (164). Such findings are neither sensitive nor specific. Malignant mesothelioma of the tunica vaginalis should be included in the differential diagnosis of a rapidly growing hydrocele, as is seen in 56.3% of reported cases. The overall prognosis in patients with malignant mesothelioma is very poor. Local recurrence of the mesothelioma was seen in 35.7% of patients who underwent resection of the hydrocele walls, whereas 10.5% and 11.5% experienced local recurrence after scrotal orchiectomy and inguinal orchiectomy, respectively (165).

Testicular Prostheses
Patients who undergo orchiectomy often elect to have a testicular prosthesis implanted. Currently, silicone testicular implants are used, and US evaluation reveals an anechoic oval structure in the hemiscrotum (1). Silicone prostheses cause moderate sound enhancement and reverberation artifacts (166). There currently is a shortage of silicone testicular prostheses, which are no longer made in the United States owing to concern about the breast implant class action lawsuit. No new medical-grade testicular prostheses are currently being manufactured, thus creating a problem for patients wishing to have a prosthesis implanted after orchiectomy.

Testicular Trauma
Testicular trauma is not uncommon and typically results from a motor vehicle accident, an athletic injury, a direct blow, or a straddle injury. Trauma can result in contusion, hematoma, fracture, or rupture of the testis. More than half of all testicular ruptures occur during sporting activity in patients who are struck in the groin. Motor vehicle accidents account for 9%–17% of testicular ruptures, while falls and straddle injuries account for the remainder (167,168). Testicular rupture is a surgical emergency, and more than 80% of ruptured testes can be saved if surgery is performed within 72 hours after injury (169,170).

US findings in testicular rupture include an interruption of the tunica albuginea, a heterogeneous testis with irregular poorly defined borders, scrotal wall thickening, and a large hematocele (171,172). Color and power Doppler US are helpful, because either can demonstrate disruption in the normal capsular blood flow of the tunica vasculosa (Fig 20). Heterogeneous intratesticular lesions are caused by hemorrhage or infarction. Direct visualization of a fracture line is rare and seen in only 17% of cases (172).

View larger version (196K): [in this window] [in a new window]   Figure 20a. Surgically proved rupture of tunica albuginea in a 34-year-old man who was struck in the groin. (a) Transverse oblique US scan of testis reveals a heterogeneous mass (arrow) in the inferior pole. (b) Color Doppler flow US scan reveals focal absence of blood flow in the tunica vasculosa (arrow), suggestive of tunica albuginea fracture. There was associated hematoma of the epididymis as well.

View larger version (169K): [in this window] [in a new window]   Figure 20b. Surgically proved rupture of tunica albuginea in a 34-year-old man who was struck in the groin. (a) Transverse oblique US scan of testis reveals a heterogeneous mass (arrow) in the inferior pole. (b) Color Doppler flow US scan reveals focal absence of blood flow in the tunica vasculosa (arrow), suggestive of tunica albuginea fracture. There was associated hematoma of the epididymis as well.

Hematomas can involve the testis, epididymis, or scrotal wall. Their US appearance varies with time. Acute hematomas appear hyperechoic and subsequently become complex with cystic components. Hematoma appears avascular on color Doppler US scans (49,55). Scrotal exploration is warranted if there is compelling scrotal US or physical examination evidence of testicular fracture or rupture. The presence of a large hematocele is another indication for exploration. Small hematoceles, epididymal hematomas, or contusions of the testis generally pose little risk to the patient and do not require surgical exploration (174).

	CONCLUSION

TOP ABSTRACT INTRODUCTION ANATOMY VASCULAR SUPPLY US EVALUATION SCROTAL WALL LESIONS INGUINAL AND SCROTAL SWELLING... CONDITIONS OF THE SPERMATIC... EPIDIDYMIS CONDITIONS OF THE TESTES... CONCLUSION REFERENCES

 
In conclusion, the use of gray-scale, pulsed, and color Doppler US can help to establish the correct diagnosis of a variety of pathologic conditions involving the scrotum. High-frequency US provides information essential to reaching a specific diagnosis in patients with testicular torsion and epididymo-orchitis, and its role in the diagnosis of scrotal trauma is also expanding. Better characterization of intratesticular nonneoplastic cystic lesions is possible with the use of high-frequency US.

Knowledge of the normal and pathologic US appearance of the scrotum, as well as application of proper US technique, is essential for accurate diagnosis of disorders of the scrotum and its contents.

	ACKNOWLEDGMENTS

 
The authors acknowledge the following individuals for their assistance with preparation of this manuscript: Virginia Wormald, Theresa Kubera, and Margaret Kowaluk. We are thankful to Martin I. Resnik, MD, Case Western Reserve University, Cleveland, Ohio, for his comments and suggestions in the preparation of this manuscript.

	FOOTNOTES

 
Abbreviations: NSGCT = nonseminomatous germ cell tumor, TM = testicular microlithiasis

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