Ultrasound of the Scrotum

Ultrasound of the Scrotum Monica Smith Pearl, MD, and Michael C. Hill, MB Ultrasound is a vital adjunct to clinical examination in diagnosing scrotal disease, as a number of different processes may present similarly. Potential applications range from the acute emergency to long-term screening as well as cases in which a distinct scrotal abnormality may or may not be palpable. Differentiating acute epididymitis/epididymoorchitis from testicular torsion is possible sonographically, thereby guiding appropriate medical or surgical management. Distinguishing between cystic, solid, or complex scrotal masses is readily performed with this modality. It clearly depicts simple versus complex hydroceles and determines the presence of underlying testicular or epididymal disease. Not only is ultrasound the best imaging modality for longitudinal screening in patients (testicular microlithiasis, cryptorchidism) at risk for testicular tumors, it also provides valuable information in the infertile male by documenting the presence or absence of a varicocele. Semin Ultrasound CT MRI 28:225-248 © 2007 Elsevier Inc. All rights reserved.

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ltrasound is the best overall imaging modality to evaluate for scrotal disease as it is portable, easy to perform, lacks ionizing radiation, and is less expensive than other imaging modalities (Table 1). Clinical evaluation alone may be insufficient for accurate diagnosis in some cases, as a variety of scrotal processes may have similar clinical manifestations and accurate physical examination may be limited by pain or the presence of a large hydrocele. From the acute emergency to long-term screening in patients at risk for developing testicular neoplasms, ultrasound provides valuable information that, when combined with the clinical data, can be used to formulate a likely diagnosis and guide appropriate management. It reliably evaluates the acute scrotum,1 differentiating acute epididymitis/epididymo-orchitis from torsion. (Torsion is discussed in another article of this volume.) It determines if a palpable abnormality arises from the testis, epididymis, or both, and whether it is cystic, solid, or complex.2,3 It characterizes the fluid of a hydrocele as simple or complex and identifies an associated underlying testicular or epididymal abnormality if one is present. In patients with testicular microlithiasis or cryptorchidism, who are at increased risk for developing testicular tumors, ultrasound is the imaging modality of choice, as it is in the infertile male in whom it can detect the presence or absence of a varicocele.

Department of Radiology, The George Washington University Hospital, Washington, DC. Address reprint requests to Michael C. Hill, MB, Department of Radiology, The George Washington University Hospital, 900 23rd Street NW, Washington, DC 20037. E-mail: [email protected].

0887-2171/07/$-see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1053/j.sult.2007.05.001

Normal Anatomy The scrotum is separated by a partial midline septum, the median raphe, into two sacs, each containing the testis, epididymis, and inferior spermatic cord.2,4 The scrotal wall, from superficial to deep layers, is composed of skin, superficial fascia, dartos muscle, external spermatic fascia, cremasteric fascia, internal spermatic fascia, and the parietal layer of the tunica vaginalis,2,4 although sonographically it appears as a single layer 2 to 8 mm thick.2 During descent into the scrotum, a peritoneal lining (processus vaginalis) fuses around the testis to form the tunica vaginalis,4 whose communication with the peritoneal cavity obliterates after birth. The outer parietal and inner visceral layers of the tunica vaginalis join at the posterolateral aspect of the testis where the tunica attaches to the scrotal wall, leaving a small bare area posteriorly of the testis and epididymis uncovered by tunica.2,4 A few milliliters of fluid, seen as a thin anechoic rim adjacent to the epididymal head, normally separates the layers of the tunica vaginalis and should not be confused with a hydrocele.2 The normal postpubertal testes are symmetric and ovoid and measure approximately 5 ⫻ 3 ⫻ 2 cm (Fig. 1). Although the testis usually has medium level homogeneous echoes,2 normal variants have been described and include a unilateral striated pattern (Fig. 2), thought to represent fibrosis,5 and hypoechoic intratesticular bands (Fig. 3), described in the middle third of the testis on axial or slightly oblique scanning planes. These bands, which can be up to 3 mm wide and 3 cm long, may contain arterial and venous components and represent a normal variant of intratesticular vessels.6 The testis is 225

M.S. Pearl and M.C. Hill

226 Table 1 Clinical Indications for the Use of Scrotal Ultrasound Clinical Setting Scrotal mass Acute scrotum Scrotal trauma Hydrocele Varicocele Higher risk for testicular tumor: testicular microlithiasis, cryptorchidism

immediately surrounded by the fibrous tunica albuginea, which can be seen as a thin echogenic line. Along its posterior border the tunica albuginea penetrates the testicular parenchyma to form the mediastinum testis, seen as an echogenic band of variable thickness. Numerous fibrous septa emanate from the mediastinum, dividing the testis into 250 to 400 lobules,2 which are not individually resolved on high-resolution ultrasound. Each lobule contains one to three seminiferous tubules that drain into a network of epithelial lined spaces within the mediastinum called the rete testis (Fig. 4). The epididymis is a 6- to 7-cm homogeneous, isoechoic to

Figure 1 Normal testis and epididymis. (A) Longitudinal and (B) transverse images show a normal testis (T), epididymis (E), and mediastinum testis (arrows).

Ultrasound Utility Cystic versus solid Testicular versus epididymal Acute epididymitis/epididymo-orchitis versus torsion Testicular rupture Simple versus complex Unilateral versus bilateral Testicular mass

slightly hyperechoic tubular structure7,8 that normally courses inferiorly along the posterior aspect of the testis and is composed of a head (globus major), body (corpus epididymis), and tail (globus minor).4,7 Drainage from the rete testis continues via 10 to 15 efferent ductules into the epididymal head, which converge into a single larger duct in the epididymal body and tail, which ultimately becomes the vas deferens.2 The epididymal head measures 5 to 12 mm in diameter,

Figure 2 Normal striated testis. (A) Longitudinal and (B) transverse scans of a normal striated testis.

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Figure 4 Diagram of the normal testis and epididymis.

is located at the superior pole of the testis, and is round, triangular, or pyramidal in shape.2,4,7,9 The body and tail are narrower, measuring 2 to 5 mm in diameter,2 and gradually taper as they course inferiorly along the testis to its lower pole. Described common variants in epididymal anatomic position include an epididymis that is entirely superior to the testis without a posterior component and an epididymis that only reaches the midportion of the testis before becoming the vas deferens.7 Four testicular appendages (appendix testis, appendix epididymis, vas aberrans, and paradidymis) have been described2 and recognizing them as normal anatomy is important as the appendix testis and appendix epididymis are well visualized sonographically,10 particularly in the presence of a hydrocele.2 The appendix testis, a Müllerian duct remnant, may be seen as a 5-mm ovoid structure arising from the upper pole of the testis in up to 80% of patients.10 It is isoechoic to the testis and may be cystic (Fig. 5).2,7 The appendix epididymis, a Wolffian duct remnant, may be seen in 6% of patients,10 although it has been described in up to 34% in postmortem series.2 It too is isoechoic to the testis but more often appears pedunculated, seen as a 5-mm stalk projecting from the epididymal head or tail.2,7 The spermatic cord is normally identified posteromedial to the testis7 and contains the following structures: vas deferens; testicular, cremasteric, and deferential arteries; pampiniform plexus of veins; nerves (genital branch of the genitofemoral nerve and testicular plexus of the sympathetic trunk); and lymphatics.11 The testicular artery, which arises from the aorta distal to the renal artery, has a low impedance pattern on duplex Doppler with high levels of diastolic flow, reflecting the low vascular resistance of the testis (Fig. 6).12 At the

Figure 3 Normal hypoechoic band. (A, B, C) Transverse scans of the upper half of the testis demonstrating the varied appearance of the normal hypoechoic band (arrows).

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Figure 5 Appendix testis. Longitudinal scan of the upper pole of the testis (T) demonstrating the appendix testis (arrow). A small hydrocele (H) is present.

posterosuperior aspect of the testis, the testicular artery divides and pierces the tunica albuginea, running peripherally in a layer called the tunica vasculosa. Here the branches are called capsular arteries, which supply centripetal branches that first course toward the mediastinum and then further subdivide into smaller recurrent rami that flow away from the mediastinum to perfuse the testicular parenchyma.9,12 Despite previous descriptions emphasizing the infrequency of arteries coursing directly through the mediastinum, transmediastinal arteries have been observed by Middleton and Bell in up to 52% of normal testes,13 are usually found in the superior half of the testis, and may be bilateral. Unlike the testicular artery, both the deferential artery, which arises from the vesical artery and supplies the epididymis and vas deferens, and the cremasteric artery, which arises from the internal iliac artery and supplies the scrotal skin, demonstrate high impedance patterns on duplex Doppler, secondary to the high vascular resistance of the epididymis and peritesticular tissues.12 Venous drainage is accomplished by the pampiniform plexus, which drains into the ipsilateral testicular vein and subsequently into the inferior vena cava on the right or the renal vein on the left.7

M.S. Pearl and M.C. Hill should be obtained, comparing the size and echogenicity of each testis on at least one transverse image. Duplex and color flow Doppler (CFD) of each testis should be documented and, if one side is abnormal, the contralateral normal side should be used to calibrate the grayscale and color Doppler gain settings.2,14 The epididymis is best evaluated in a longitudinal view and the echogenicity and size of each should also be compared.2 Ultrasound evaluation of both palpable and nonpalpable scrotal masses15 provides information that narrows the differential diagnosis3 and guides management.16,17 If a scrotal mass is palpable, one hand stabilizes the testis and maintains anatomic orientation, while the other hand performs direct scanning over the abnormality to provide direct sonographic correlation.18 After identification of a mass, the presence of internal vascularity should be determined. Incidental detection of nonpalpable focal testicular lesions is increasing, likely secondary to both technologic improvements and the use of ultrasound in infertile and asymptomatic patients, both of whom have higher rates of benign lesions compared to the general population.17 Thus, intraoperative ultrasound, which localizes the nonpalpable mass and guides excision, is likely to become increasingly utilized for conservative surgery,17,19 an important treatment option versus orchiectomy,

Imaging Techniques Scrotal imaging is best performed with a high-frequency 7- to 12-MHz linear array2 transducer; however, in the presence of a large hydrocele, a lower frequency transducer that provides deeper penetration may be needed to optimally visualize the underlying testis and epididymis. The scrotum should be placed on a towel supported by the closed thighs and the patient should hold the penis away from the scanning field. A liberal amount of gel should be used to provide ample acoustic contact between the transducer and the scrotal skin. Three longitudinal (midline, medial, lateral) and three transverse (upper pole, mid-portion, lower pole) images of each testis

Figure 6 Duplex and CFD imaging of the normal testis. Longitudinal scan of the testis demonstrating arterial and venous (below the baseline) flow in a normal testis. (Color version of figure is available online.)

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Figure 7 Intraoperative ultrasound of the testis. This was used to perform guided biopsies of two hypoechoic masses (M) secondary to sarcoid.

as up to 80% of nonpalpable testicular lesions have been shown to have a benign histology (Fig. 7).17 The structures within the scrotal sac are examined to detect extratesticular abnormalities, with scanning starting at the level of the spermatic cord and moving inferiorly to the level of the pampiniform plexus. To evaluate for a varicocele, the patient should be scanned while performing a Valsalva maneuver, preferably in the upright position.

The Testis Testicular Tumors Testicular tumors account for less than 2.0% of all malignant neoplasms in men.9 The usual clinical presentation is a painless, palpable testicular mass or diffuse testicular enlargement.20,21 A minority of patients may initially present with extragonadal disease in the retroperitoneum or mediastinum before clinical discovery of a palpable testicular mass,20 and it is in these cases that ultrasound becomes an important test22 to detect and confirm that the testis is the primary site of involvement.20 Ninety-five percent of primary testicular tumors are derived from germ cells, which are generally malignant, and are subdivided into seminomatous versus nonTable 2 Primary Testicular Tumors Germ Cell Tumors Seminoma (40%) Nonseminomatous Mixed germ cell ³(40%) Embryonal cell carcinoma Yolk sac (endodermal sinus tumor) Teratoma (25–30%) Choriocarcinoma Stromal tumors (5%) Leydig cell tumor Sertoli cell, granulosa cell Primitive gonadal stromal tumors

Figure 8 Seminoma. (A) Grayscale and (B) CFD images of a seminoma (S). The tumor is solid and occupies most of the testis giving it a lobulated contour. (Color version of figure is available online.)

seminomatous germ cell tumors (Table 2),2,21 as seminomas have a better prognosis and are radiosensitive. The remaining primary testicular tumors originate from gonadal stromal or sex-cord derivatives, which are usually smaller and generally benign.21 Ultrasound can detect virtually all testicular tumors by

230 identifying changes in the normally homogeneous echo texture of the testis.23 It answers the important clinical question of whether a palpable mass is intratesticular with a 90 to 95% rate of malignancy24 or extratesticular and more likely to be benign.18 An overall malignancy rate of 3% is reported in a review of 91 patients with extratesticular masses who underwent surgical resection25; however, a more recent study of 19 patients suggests that the frequency of malignancy may be as high as 16%.24 Malignant testicular tumors are predominantly hypoechoic (92%)16; however, benign diseases such as infarct, which can be seen as a triangular-shaped avascular lesion,26 or focal orchitis may have a similar appearance.23 Additionally a broad spectrum of echo texture patterns has been described for testicular malignancies16 including diffuse parenchymal echo texture change or bright echogenic foci, which correlate histologically with bone, cartilage, calcification, or fibrosis.23 Furthermore, hemorrhage or necrosis may also complicate the echo pattern. Thus, combining clinical history with sonographic findings is important, as accurate prediction of malignancy or histologic classification cannot reliably be made on ultrasound findings alone.16,17 Duplex and CFD may be used to detect intratumoral vascularity, which depends more on tumor size than histology. In a study of 28 patients with surgically proven testicular tumors, 95% of tumors greater than 1.6 cm demonstrated increased vascularity, whereas histology showed no correlation with vascularity.27 CFD may be especially important for pediatric testicular tumors, particularly in prepubertal patients, in which cases CFD detects hypervascularity in an enlarged testis of normal echo texture.28 Doppler ultrasound is also helpful in the patient with a presumed testicular mass and a history of trauma. The detection of internal vascularity suggests neoplasm, while its absence would require follow-up to complete resolution to ensure a nonneoplastic etiology, as 86% of tumors less than 1.6 cm have been shown to be hypovascular.27

Germ Cell Tumor Seminoma is the most common germ cell tumor29 and accounts for approximately 50% of germ cell tumors.2 It occurs in patients 30 to 50 years of age and has a favorable prognosis, as 75% lack metastases at diagnosis and they respond well to radiation and chemotherapy.16,22,23,30 Although uncommon, they can be bilateral, with the incidence of a contralateral synchronous or metachronous tumor of approximately 2 to 5%. The sonographic appearance is typically a homogeneous well-defined hypoechoic lesion, as calcifications and cystic areas of necrosis are less common than in nonseminomatous tumors (Fig. 8).9,16 Larger lesions tend to be more heterogeneous and some seminomas may be poorly marginated, diffusely infiltrative, and even multifocal.18 Nonseminomatous germ cell tumors occur in a slightly younger population (25-35 years) and are more aggressive, invading the tunica albuginea and frequently with metastases at the time of discovery.16,18,23,30 The overall 5-year survival is less favorable than seminoma, as they are not as sensitive to radiation therapy. Seventy percent produce serum hormonal

M.S. Pearl and M.C. Hill makers such as alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG), which are useful in diagnosis and in monitoring treatment response. Unlike typical seminomas, ultrasound examination shows a heterogeneous lesion secondary to internal hemorrhage, cystic changes, and calcification.2,9 Nonseminomatous germ cell tumors are subdivided into embryonal cell carcinoma, yolk sac or endodermal sinus tumor, teratoma, and choriocarcinoma. Mixed germ cell tumor (40%) is more common than any pure nonseminomatous germ cell tumor, can be multifocal, and may contain various elements of seminomatous and nonseminomatous germ cell tumors (Figs. 9 and 10).9 Pure embryonal cell tumors are less common, representing 25% of germ cell tumors, and appear heterogeneous commonly with cystic areas (30%)9 and echogenic foci with or without acoustic shadows,16 which correspond to areas of hemorrhage or calcification.18 Endodermal sinus or yolk sac tumors occur most often in children younger than 5 years of age, produce AFP, and are hypervascular. They may contain echogenic foci secondary to hemorrhage; however, normal echogenicity has also been described.2,28 Teratomas are categorized as mature, immature, and those that have undergone malignant transformation. They occur in any age group and are the second most common testicular tumor in prepubertal males after endodermal sinus tumors.2 Those found in the early years of life have mature histology, are well differentiated and are more often benign, in contrast to adults, where the tumor has immature elements coexisting with other malignant cell types, producing elevated levels of serum AFP and hCG.9 Like other nonseminomatous tumors, teratomas are heterogeneous with cystic areas and echogenic foci with acoustic shadowing due to calcification, cartilage, immature bone, and fibrosis. Choriocarcinoma is the least common type, representing approximately 2% of primary germ cell tumors9 but is frequently (23%) a component of mixed germ cell tumors. A highly malignant tumor, choriocarcinoma develops metastasizes early9 via hematogenous and lymphatic routes and produces an elevated serum hCG level. In a minority of patients, extragonadal metastatic disease may be the initial presentation before clinical discovery of a palpable testicular mass20 and it is in these cases that ultrasound becomes an important adjuvant test22 to detect and confirm that the testis is the primary site of involvement. Rarely found in the pure form, choriocarcinoma has a sonographic appearance that is usually dominated by the other cell types; however, the focus of choriocarcinoma is like other nonseminomatous germ cell tumors: heterogeneous secondary to hemorrhage or necrosis, appearing as mixed cystic and solid components.2,9 In some instances a regressed or “burned-out” testicular germ cell tumor may be seen as a focal area of echogenicity within a normal- to small-sized testis.23 Acoustic shadowing may be present; however, no associated soft-tissue component should be seen. If the echogenic foci are associated with a mass, differentiation between viable tumor and scar is not possible without serial observation or pathologic correlation.23,33 One theory for this appearance involves rapid tumor

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Figure 10 Multifocal mixed germ cell tumor. Longitudinal scan of the testis demonstrating multiple discrete hypoechoic masses (arrows).

suggested, as most of these patients demonstrate Leydig cell hyperplasia.35 Small Leydig cell tumors are hypoechoic with characteristic increased peripheral vascularity,36 while larger tumors are more complex due to necrosis and hemorrhage. Sertoli cell tumors are rare (1%)37 and lead to feminization and gynecomastia.38 These tumors are usually small and hypoechoic; however, large-cell calcifying Sertoli cell tumor is a distinct subtype of Sertoli cell tumor with unusual features including bilaterality and multifocality,37,39 which may occur in isolation or in association with genetic abnormalities in-

Figure 9 Mixed germ cell tumor of the testis. (A) Grayscale and (B) duplex and CFD images of a mixed germ cell tumor (G) with cystic and solid areas. (Color version of figure is available online.)

growth, outgrowing its blood supply leading to involution, fibrosis, and calcification.

Stromal Tumors Stromal tumors make up approximately 5% of testicular tumors and contain fibroblasts along with Leydig, Sertoli, theca, granulosa, and lutein cells in various degrees of differentiation. When stromal elements coexist with germ cell elements, the tumor is called a gonadoblastoma. The most common tumor is a Leydig cell tumor, which constitutes approximately 2% of testicular tumors,21 and occurs in children aged 3 to 6 years as well as in adults in the third to fifth decades. Patients present with a painless testicular mass and an elevated serum androgen or estrogen level leading to precocious puberty, gynecomastia, impotence, and virilization.21,34 An association with Klinefelter syndrome has been

Figure 11 Testicular lymphoma. (A) Longitudinal scan of the right testis and (B) transverse scan of the left testis demonstrating bilateral hypoechoic testicular masses (L). Notice that the tumor on the left has invaded through the tunica albuginea (arrows).

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232 cluding Peutz–Jeghers syndrome, tuberous sclerosis, and Carney’s complex.32,39-41 The testicular tumors characteristic of Carney’s complex include large-cell Sertoli cell tumors, Leydig cell tumors, and adrenocortical rest tumors.42 Recognition of this complex, originally described as a complex of myxomas, spotty pigmentation, and endocrine abnormalities, is important as cardiac myxomas have potentially lethal complications.40

Metastatic Testicular Tumor Metastatic disease to the testes is usually found in patients over 50 years of age. Testicular non-Hodgkin’s lymphoma, which accounts for up to 7% of all testicular neoplasms and 25 to 50% of testicular neoplasms in men over age 50,43-46 is the most common testicular metastasis, although testicular involvement occurs in less than 1% of patients with lymphoma.9,44,47 Frequently bilateral, with synchronous or metachronous involvement reported in up to 40%,43 lymphoma is the most common cause of bilateral testicular masses. The testes may be the only site of involvement in 10% of cases; however, subsequent evaluation will demonstrate extratesticular disease in 25%, likely secondary to the biologic aggressiveness of primary testicular lymphoma and its behavior as a systemic disease.43 Additionally, the testis is commonly the site of extramedullary relapse after chemotherapy-induced remission because the blood–testis barrier inhibits accumulation of chemotherapeutic agents.44 Sonographically testicular lymphoma is hypoechoic, focal or diffusely infiltrative, maintains the normal ovoid testicular shape,44 and is homogeneous, as hemorrhage, necrosis, and calcifications are rarely present (Fig. 11). Unlike germ cell tumors, extension to involve the epididymis and spermatic cord is common and may occur in as many as 60% of cases.48 Duplex and CFD demonstrate hypervascularity, regardless of tumor size, which is in contradistinction to previous reports by Horstman et al documenting hypovascularity in testicular tumors less than 1.6 cm.27,44 This hypervascularity may mimic acute epididymo-orchitis; however, clinical history is a discriminating factor. Testicular infiltration with leukemia is primarily a childhood disease, present in up to 8% of children with leukemia. It is rarely clinically apparent in adults,44 most commonly occurs in the acute phase of disseminated disease (64%), and is often bilateral.47 Leukemia is similar to lymphoma in its sonographic appearance, demonstrating hypervascularity and hypoechoic focal or diffuse regions, as well as its predilection for the testis as the first site of extramedullary relapse,

Table 3 Metastatic Testicular Tumors Lymphoma Leukemia Prostate Lung Gastrointestinal tract: stomach, colon, pancreas Melanoma Kidney

Figure 12 Testicular cyst. (A) Transverse scan of a well-defined, hypoechoic cyst (arrow) with through transmission adjacent to the mediastinum testis. (B) Longitudinal CFD image of a well-defined testicular cyst (arrow) that is avascular, full of echoes, and with good through transmission. (Color version of figure is available online.)

most commonly described in children with acute lymphoblastic leukemia.44,49 Testicular plasmacytoma is a rare finding not only as part of multiple myeloma, with an incidence between 0.6 and 2.7%, but also as a primary testicular tumor.31,50 As few as 51 cases have been reported in patients ranging from 26 to 89 years and the incidence of testicular and epididymal plasmacytomas described is less than 0.1% of all testicular tumors.50 Extramedullary plasmacytomas may involve a variety of anatomic sites, most commonly the respiratory tract, gastrointestinal tract, and lymph nodes. Less common is gonadal involvement; however, when present, it may involve the testis, epididymis, or both,51 is generally associated with diffuse

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Figure 13 Cyst of the tunica albuginea. (A) Simple and (B) complex tunica albuginea cysts (arrows).

disease, and has a similar sonographic appearance to lymphoma and leukemia. Metastases to the testis may also originate from the prostate, lung, malignant melanoma, kidney, and gastrointestinal tract (stomach, colon, pancreas) (Table 3),2,52,53 which, at the time of occurrence, usually involves other sites. More common in patients older than 50 years, testicular metastases are often multiple and may be bilateral (15%). Sonographically they are generally hypoechoic but may be complex and even echogenic. Routes of spread include hematogenous, retrograde venous or lymphatic, and direct invasion.53

Benign Testicular Cysts Characteristic sonographic features of benign scrotal lesions can help direct medical or conservative surgical manage-

Figure 14 Tubular ectasia. (A) Longitudinal and (B) transverse scans of tubular ectasia (arrows). (C) CFD image of tubular ectasia (arrows) with adjacent testicular cyst (C). The CFD image proves that the area of tubular ectasia is not an intratesticular varicocele. (Color version of figure is available online.)

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M.S. Pearl and M.C. Hill choic and hypoechoic layers correspond to layers of keratin and desquamated squamous epithelium. A “bull’s-eye” or “target” appearance refers to a halo surrounding an echogenic center, which may represent a central nidus of calcification. An epidermoid cyst may also appear as a well-defined mass with an echogenic rim that may or may not be calcified. Although they are benign lesions, treatment involves excision as distinction from other germ cell tumors is not always possible.

Tubular Ectasia and Cystic Dysplasia Tubular ectasia, a benign dilatation of the seminiferous tubules in the rete testis, occurs most often in men older than

Figure 15 Testicular calcification. Longitudinal scan of the testis demonstrating a small hyperechoic focus in the testis consistent with testicular calcification (arrow).

ment, as not all intratesticular lesions are malignant.54,55 Testicular cysts are present in up to 10% of patients over the age of 40 years, increase in incidence with age,56 and can be divided into intratesticular (Fig. 12) and extratesticular cysts, the latter of which is further subdivided into tunica albuginea cysts and epididymal cysts.57 Intratesticular cysts are usually simple cysts characterized by a thin, well-defined, smooth wall containing anechoic fluid with good through transmission. They are usually not palpable, vary in size from 2 mm to 2 cm, and are found adjacent to the mediastinum testis.2,58 They can be distinguished from testicular tumors that have undergone cystic necrosis which have a thick, irregular wall and may contain septa and debris. Tunica albuginea cysts appear between the fifth and sixth decades of life and are uncommon lesions, with an incidence of less than 1%.57 The epithelial lining varies from low cuboidal to columnar cells and they are thought to be mesothelial in origin.59 They range in size from 2 to 5 mm and are usually asymptomatic, discovered by palpation as a small testicular mass.2,58 These cysts may be single or multiple, unilocular, or multilocular, and when complex, may mimic a testicular tumor (Fig. 13).56,60 Cysts of the tunica vaginalis may also have a similar appearance. Testicular epidermoid cysts are benign and relatively uncommon, accounting for 1 to 2% of all testicular lesions.61 Recognition is important as local excision rather than orchiectomy may be performed for treatment.62,63 Primarily occurring in the second to fourth decades, they usually present as a painless testicular mass; however, 10% of patients may experience scrotal pain or diffuse testicular swelling.63 They are well defined and avascular with CFD showing no blood flow within the cyst.2 These cysts range in size from 1 to 3 cm and are usually single; however, one case of bilateral epidermoid cysts and four cases of multiple cysts have been reported.61 Various sonographic appearances have been described with the classic “onion ring” pattern considered characteristic.2,64 The alternating hypere-

Figure 16 Intratunical calcifications. (A) Longitudinal scan demonstrates a mobile intratunical calcification (arrow) at the inferior pole of the testis (T). (B) This calcification is palpable to the examining finger (F).

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235 the seminiferous tubules.69,73,74 Microlithiasis may be found incidentally in patients presenting for a scrotal ultrasound (1-2%) or be associated with cryptorchidism, Klinefelter syndrome, Peutz–Jeghers syndrome, and Down syndrome and in patients with infertility.69,75,76 They have been associated with an increased risk of germ cell tumor (5-10%) in both the diffuse and the limited forms (Fig. 18).77 Although more than 90% of patients with testicular microlithiasis were not associated with testicular tumor in a large study by Middleton et al,71 there is now general agreement that it does increase the risk of testicular tumor and so current recommendations for these patients include annual sonographic surveillance along with periodic self-examination for the early tumor detection.69,74,77-79

Figure 17 Testicular microlithiasis. Longitudinal scan of a testis with multiple punctate calcifications consistent with testicular microlithiasis.

55 years of age and is caused by epididymal obstruction secondary to trauma or inflammation. Most are associated with an extratesticular abnormality, specifically a spermatocele, and bilateral involvement, which may be asymmetric, is common.65,66 Sonographically, small tubular or round anechoic structures are seen within the mediastinum testis, beginning at the periphery and extending a variable distance within the testis (Fig. 14).67 Cystic dysplasia is rare and is an embryologic failure of the tubules of the rete testis to join with the efferent ductule.68 This is found in infants and young children and there may be coexistent renal agenesis. Sonographically, cystic dysplasia can mimic tubular ectasia of the rete testis; however, in cystic dysplasia, the cystic areas extend beyond the mediastinum testis, into the testicular parenchyma, and produce parenchymal atrophy.

Sarcoidosis Involvement of the testis and the epididymis with sarcoid is rare, occurring in less than 1% of patients with the systemic disease.80 Clinically it presents as a painless epididymal, or less commonly, a testicular, mass or as an acute/recurrent epididymitis. Sonographically the lesion is a hypoechoic, irregular mass that may be calcified, multifocal, and bilateral (Fig. 7).81 Definitive distinction from tumor may not be possible and biopsy or excision may be necessary for diagnosis.

Testicular and Extratesticular Calcification Parenchymal testicular calcifications (Fig. 15) may be found in germ cell tumors, “burned out” germ cell tumors, and sertoli cell tumors and secondary to prior trauma, infection (tuberculosis), infarction, and inflammation (sarcoidosis).69 Localized calcification may also be found on the surface of the tunica albuginea and may slough off into the fluid between the layers of the tunica to form a “scrotal pearl” (Fig. 16). These freely mobile calcifications are secondary to inflammation of the tunica vaginalis, appendix testis, or appendix epididymis and are often associated with a hydrocele. Testicular microlithiasis is identified as small 1- to 3-mm echogenic foci, which may produce a comet tail artifact, within the testicular parenchyma (Fig. 17).69 It usually occurs bilaterally69,70 and may be diffuse, also referred to as classic, or limited (less than five hyperechoic foci per image),71 which is associated with a lower rate of malignancy than classic microlithiasis.72 It is postulated that these may be due to defective phagocytosis of degenerate tubular cells by the Sertoli cells, resulting in calcified cellular debris within

Figure 18 Bilateral testicular microlithiasis with a mixed germ cell tumor. (A) Longitudinal scan of the left testicle with testicular microlithiasis. (B) Longitudinal scan of the right testicle with testicular microlithiasis and a predominantly solid appearing mixed germ cell tumor (G) containing punctuate calcifications.

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Adrenal Rests Testicular adrenal rests arise from aberrant adrenal cortical cells and usually present as a palpable testicular mass.82 In adrenogenital syndrome (autosomal-recessive), Addison’s disease, and Cushing’s syndrome, the elevated levels of serum ACTH stimulate these rests to grow and produce multifocal, and possibly bilateral, hypoechoic masses in the testes.83 Some of these masses may have echogenic foci due to fibrosis. On CFD, a “spoke-wheel” pattern of vascularity has been described.82,84 The true origin of these masses can be diagnosed in the appropriate clinical setting. In congenital adrenal hyperplasia, the disease is detected in the neonatal period with or without salt wasting or in early adulthood with precocious puberty. The adrenal rests regress with glucocorticoid administration, further supporting the diagnosis.82 Cryptorchidism The normal testis descends through the inguinal canal into the scrotum at 36 weeks of gestation and is guided by the gubernaculum testis, which arises from the inferior pole of the testis and is attached to the scrotum.85 Undescended testis has a prevalence of 3 to 5% in newborns, but the rate decreases to 0.8% by 1 year of age as many descend spontaneously.86,87 Eighty percent of undescended testes are clinically palpable and may be bilateral in up to 25%.86,88 Of the 20% that are impalpable, 80% are within the inguinal canal

Figure 19 Cryptorchid testis. Longitudinal scans of (A) a cryptorchid testis (C) in the left inguinal canal and (B) the normally descended right testis (T) in the scrotum. Note that the cryptorchid testis is more hypoechoic than the normal testis.

Figure 20 Epididymal cysts. Longitudinal scans of the testis showing (A) a small epididymal cyst (arrow), (B) a large epididymal cyst (C) with a septum (arrow), and (C) an epididymal tail cyst (C).

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Figure 21 Adenomatoid tumor of the epididymis. Longitudinal scan demonstrating a solid mass (M) in the head of the epididymis. The echogenicity is equal to that of the adjacent testis (T).

Figure 23 Acute epididymitis involving the head and body. Longitudinal (A) grayscale and (B) CFD images of the testis (T) and epididymis (E) demonstrate an enlarged hypervascular epididymis. (Color version of figure is available online.)

Figure 22 Fibrous pseudotumor. (A) Longitudinal and (B) transverse images of fibrous pseudotumor show a well circumscribed hypoechoic solid mass (arrows) arising from the tunical surface of the testis (T). The contralateral testis (not shown) also had two similar lesions.

and the remaining 20% can occur anywhere in the abdomen from the lower pole of the ipsilateral kidney to the internal inguinal ring.86 Two important complications of undescended testis are infertility, as the testis must reside in the scrotum to fully mature, and testicular malignancy.86 The risk of malignancy is 20 to 46 times higher than males with normally descended testes and malignant degeneration usually occurs to seminoma.87 To reduce the risk of infertility and tumor, orchilpexy is performed; however, despite surgical treatment, the risk of tumor development remains greater than the normal patient in both the surgically corrected undescended testis and the contralateral normally descended testis.86 Sonographically, the undescended testis is small and hypoechoic in comparison to the normal testis (Fig. 19). Identification of the mediastinum testis confirms that the structure is the testis and not a lymph node or the pars infravaginalis gubernaculi, which is the inferior bulbous por-

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Spermatoceles, which may be secondary to prior trauma or infection, are more common, contain thick milky fluid composed of fat globules and cellular debris, and usually arise in the epididymal head. Epididymal cysts may arise throughout the epididymis and contain clear serous fluid (Fig. 20).2 Both cysts have a similar ultrasound appearance and loculations and septations may occur. Rarely, a spermatocele can be echogenic. Following vasectomy, the epididymis may enlarge, become heterogeneous and nodular, and may develop cysts in up to 45% of patients. The cysts are the result of tubular dilatation and congestion along with formation of spermatoceles and sperm cell granulomas, which are granulomatous reactions to extravasated sperm cells in the soft tissues surrounding the epididymis. Other causes of sperm granulomas are prior trauma or infection. Most patients are asymptomatic; however, 3% may experience chronic scrotal pain (post vasectomy syndrome) that may require epididymo-vasectomy to alleviate symptoms.2 Sonographically sperm granulomas appear as well-defined, solid hypoechoic or heterogeneous masses in the epididymis that may contain calcifications92 and may mimic an intratesticular mass.93,94

Epididymal Tumors Extratesticular tumors are rare and usually arise from the epididymis, with adenomatoid tumor comprising 30%. It is a

Figure 24 Acute epididymitis involving the tail. Longitudinal (A) grayscale and (B) CFD images demonstrate an enlarged hypervascular epididymal tail (E). Testis (T). (Color version of figure is available online.)

tion of the gubernaculum testis. Ultrasound is approximately 70% accurate89 in localizing the undescended testis; however, accurate detection of intra-abdominal testis falls to less than 50%.87 If ultrasound fails to identify the testis, magnetic resonance imaging (MRI) should be performed as diagnostic accuracy in locating undescended abdominal testes has been reported as 90%.87,90 If MRI fails, then laparoscopic exploration may be indicated due to the high risk of tumor development in the undescended testis.91 Cryptorchidism is further discussed in a separate article in this volume.

The Epididymis Epididymal Cysts Extratesticular cysts are more common than intratesticular cysts and two types are found: spermatoceles and epididymal cysts. They are frequently incidental findings (40%), especially in older men, and may be multiple (30%) and bilateral.

Figure 25 Scrotal wall edema secondary to acute epididymitis. Transverse scan through the median raphe demonstrating bilateral epididymitis (E) with scrotal wall edema (arrows).

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239 with an intramural solid component to an almost completely solid mass2 and can occur bilaterally.96 Metastases to the epididymis are rare and the most common primary sites include the testis, stomach, kidney, prostate, colon, and pancreas. A focal echogenic area in the epididymis and a hydrocele are the most common sonographic findings. Other rare extratesticular tumors are usually mesenchymal in origin and include benign (fibroma, lipoma, leiomyoma, hemangioma, and neurofibroma) and malignant (fibrosarcoma, liposarcoma, malignant histiocytoma, rhabdomyosarcoma) tumors and lymphoma.

Fibrous Pseudotumor

Figure 26 Acute epididymitis with a focal epididymal abscess. Transverse scan of the testis (T) and epididymis show a focal, well-circumscribed mass with a hypoechoic rim consistent with an epididymal abscess (arrows). A small to moderate simple hydrocele (H) is present.

benign neoplasm found in patients from 18 to 79 years and usually arises from the epididymal body; however, on occasion it may be found in the spermatic cord or adjacent testicular parenchyma. Sonographically adenomatoid tumor is seen as a unilateral, solitary, well-circumscribed mass that is usually less than 2.0 cm with variable echo textures from hypoechoic to isoechoic to hyperechoic (Fig. 21).95 Papillary cystadenoma of the epididymis is a hamartomatous tumor often associated with Von Hippel–Lindau disease.2,96 The ultrasound appearance ranges from a cystic mass

Fibrous pseudotumor is a rare, reactive proliferation of inflammatory and fibrous tissue that primarily involves the tunica vaginalis (75%) and epididymis (10%).97,98 Although benign, it may clinically mimic a testicular malignancy.99 It is thought to occur secondary to trauma, surgery, infection, or inflammation in patients in the third to sixth decades, with involvement before 18 years of age considered very rare.98,100,101 Fibrous pseudotumor appears sonographically as a paratesticular mass or masses with variable echogenicity (hypoechoic, hyperechoic, mixed echogenicity), reflecting the mixture of fibrous and cellular components and the presence or absence of calcification (Fig. 22). A hydrocele is present in approximately 50%; however, this is nonspecific.98

Scrotal Infections Epididymitis and Epididymo-Orchitis Epididymitis and epididymo-orchitis are common causes of acute scrotal pain, with etiologies differing in the affected age group. In adolescents many cases are due to sexually transmitted diseases such as gonorrhea and chlamydia. In prepubertal boys and men over 35 years of age, a lower urinary tract infection caused by Escherichia coli, proteus, pseudomonas, or klebsiella is more often the cause.2 Less common etiologies

Figure 27 Acute epididymo-orchitis. (A) Longitudinal scan showing an inhomogeneous echo pattern in the testis (T) and an enlarged epididymis (E). (B) Transverse scan of both testes contrasting the normal testis (T) with the abnormal side (arrows).

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Figure 29 Testicular abscess. (A) Longitudinal and (B) transverse images of a complex mass in the testis due to an abscess (A).

include hematogenous spread of infection, infection of a traumatic hematoma, and rarely, syphilis, tuberculosis, sarcoidosis, brucellosis, and mumps.102-106 Patients present with scrotal pain, swelling, fever, and dysuria with or without urethral discharge.

Figure 28 Acute epididymo-orchitis. Longitudinal scans demonstrating (A) an enlarged epididymal head (E), (B) a testis (T) with a normal grayscale appearance, and (C) a duplex and CFD image revealing a hypervascular testis consistent with acute epididymoorchitis. (Color version of figure is available online.)

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241 on CFD.110 Left untreated, the pressure of the intratesticular edema may compromise blood flow leading to infarction. CFD will demonstrate absence of blood flow in the affected testis with surrounding reactive hyperemia and in severe cases there may be reversal of flow during diastole, suggestive of infarction.2 Testicular abscess is most commonly associated with acute epididymo-orchitis, although it may also result as a complication of torsion or superinfection of a necrotic tumor or traumatic hematoma. Systemic infection such as tuberculosis, typhoid, mumps, smallpox, and scarlet fever may all lead to a testicular abscess.103,106 Sonographically the testis is enlarged and contains a complex fluid collection, which can mimic a necrotic tumor (Fig. 29).111,112 This is especially true if the abscess has been partially treated; however, the clinical features and follow-up, if necessary, can usually resolve this diagnostic dilemma. An abscess can rupture through the tunica vaginalis and produce a pyocele and even a fistula to the overlying skin, especially in tuberculosis.103,104 Chronic epididymo-orchitis may be secondary to incomplete treatment of acute epididymo-orchitis or tuberculosis. The testis and epididymitis are enlarged and the tunica vaginalis is thickened. The echo pattern is heterogeneous and course calcifications are frequently present. Another chronic change that has been described is a striated appearance to the testis secondary to septal fibrosis. This is a nonspecific finding, however, as it may follow torsion or be seen in elderly patients due to seminiferous tubular atrophy and sclerosis. Chronic findings of testicular infarction can follow acute epididymo-orchitis with focal wedge-shaped hypoechoic areas due to fibrosis or an overall atrophic hypoechoic or heterogeneous testis.

Scrotal Trauma Figure 30 Testicular hematoma secondary to trauma. (A) Longitudinal and (B) transverse scans of the testis (T) demonstrate a focal hypoechoic area (arrows) deep to the capsule consistent with a localized hematoma. The patient had prior direct trauma with a baseball. On follow-up scans this finding disappeared.

Sonographic findings include an enlarged hypoechoic epididymis with involvement of the head, body, tail, or entire epididymis (Figs. 23 and 24). Associated signs of inflammation such as reactive hydrocele or pyocele and scrotal skin thickening are often present (Fig. 25).107 The epididymis may appear hyperechoic and more heterogeneous if hemorrhage is present. Additionally, abscess formation may complicate acute infection (Fig. 26).108 CFD in cases of acute epididymitis and acute epididymo-orchitis will show hypervascularity in the epididymis and possibly in the testis compared to the normal side (Fig. 27), which becomes particularly useful in cases in which no grayscale abnormalities are present (Fig. 28).108,109 Although isolated orchitis can occur, it is usually found in association with acute epididymitis (20-40%).2 Testicular involvement may be diffuse or focal, appearing as multiple hypoechoic intratesticular lesions, with increased blood flow

The scrotum may be injured by blunt or penetrating trauma.113,114 Ultrasound plays a critical role in triage by stratify-

Figure 31 Testicular infarct secondary to trauma. Irregular, wedgeshaped hypoechoic areas (arrows) in a subcapsular location consistent with infarct following trauma. Testis (T).

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Figure 33 Testicular rupture secondary to trauma. (A) Longitudinal and (B) transverse scans of the testis (T) with a hematoma (H) along with testicular disruption (arrows).

Figure 32 Scrotal hematoma. (A) Transverse grayscale image demonstrating a normal testis (T) with an intact tunica (arrows) and a large extratesticular hematoma (H). (B) Transverse CFD image shows normal intratesticular flow with no vascularity of the adjacent hematoma (H) to suggest disruption of the tunica albuginea. (Color version of figure is available online.)

ing patients according to severity of injury. It accurately identifies patients with less serious injuries (hydroceles, hematoceles, scrotal hematomas), which may be managed conservatively, and patients with testicular rupture, who require urgent surgical repair.114 Provided surgery is performed within 72 hours, there is a 90% rate of salvage. Sonographic evaluation in these patients is difficult due to

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243 torsion, infection (acute epididymitis, acute epididymo-orchitis), or testicular neoplasm and may contain serous fluid (simple hydrocele), pus (pyocele), or blood (hematocele). Congenital hydroceles are the result of a patent processus vaginalis that permits entry of peritoneal fluid into the scrotal sac; however, this usually resolves within a year and a half of life.2 The simple hydrocele is a common cause of scrotal swelling and may be unilateral or bilateral. Ultrasound evaluation is particularly useful in evaluating these patients as clinical evaluation of the underlying testis and epididymis is limited. Sonographically the fluid surrounds the anterolateral margins of the testis as posteriorly the testis is adherent to the epididymis and scrotal wall. The fluid is usually anechoic with good sound transmission (Fig. 34); however, it may contain low-level echoes due to fibrin bodies or cholesterol crystals.117 Complex hydroceles have internal septations and loculations and may calcify if they become chronic (Fig. 35).

Varicocele A varicocele, which is an abnormal dilatation of the pampiniform plexus, is present in approximately 15 to 20% of adult

Figure 34 Simple hydrocele. Transverse scan of a normal testis (T) with a moderate sized simple hydrocele (H).

severe pain and swelling and must be performed in a very gentle fashion. Findings include a localized area of heterogeneous echo texture secondary to hemorrhage (Fig. 30) and infarction (Fig. 31). The testicular outline may be irregular and loss of contour definition is highly sensitive (100%) and specific (93.5%) for testicular rupture.113,114 This can be confirmed sonographically if intratesticular contents are seen projecting beyond the normal confines of the tunica albuginea. In up to a third of cases, an associated complex hematocele or scrotal hematoma (Fig. 32) is present and CFD helps distinguish vascularized extruded intratesticular contents in testicular rupture (Fig. 33) from an avascular epididymal hematoma or hematocele.115 In some patients, injury will be limited to the epididymis, resulting in traumatic epididymitis that can sonographically mimic acute infectious epididymitis. Clinical history is the discriminating factor as ultrasound findings are similar: focal or diffuse hyperemia and epididymal enlargement.116

Hydrocele A few milliliters of serous fluid are normally present in the potential space between the parietal and visceral layers of the tunica vaginalis. A hydrocele is an abnormal collection of fluid in this space and has a number of etiologies, which reflect the type of fluid accumulated. It may be idiopathic or secondary to trauma, prior inguinal hernia repair, testicular

Figure 35 Complex hydrocele secondary to acute epididymitis. Longitudinal scans demonstrating (A) a complex hydrocele (H) and (B) a complex hydrocele with an enlarged epididymis (E) and normal testis (T) secondary to acute epididymitis.

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Figure 37 Intratesticular varicocele. (A) Longitudinal, (B) transverse, and (C) CFD images of an intratesticular varicocele (arrows). Note the extratesticular varicocele (V) on image B. (Color version of figure is available online.)

men and may be primary (idiopathic) or secondary.118,119 The veins of the pampiniform plexus normally range from 0.5 to 2.0 mm in diameter, and those with an internal diameter greater than 3 mm are considered abnormal. Primary varicoceles, which usually present in patients between 15 and 25 years, are due to incompetent valves in the testicular veins and are predominately left sided (98%) because the left testicular vein has a longer, more vertical course, enters the left renal vein at a right angle, and may be compressed by the left testicular artery and descending colon.119 They are frequently bilateral (70%) and are more evident when the patient stands or performs a Valsalva maneu-

Figure 36 Varicocele. (A) Transverse, (B) longitudinal, and (C) CFD images of a large left-sided varicocele (V). Testis (T). (Color version of figure is available online.)

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245 ver. Although most males with a varicocele are not infertile, varicoceles are present in up to 21 to 39% of men with infertility119,121 and diagnosis is important as treatment improves sperm quality in as many as 53% of cases.2,122 The subclinical (nonpalpable) varicocele and its relationship to infertility is less clear; however, a strong correlation with infertility has been suggested by Gonda et al, as postoperatively all 20 patients showed improvement in semen quality and 40% became fertile.119 Secondary varicoceles are due to testicular vein obstruction in the retroperitoneum by a mass, marked hydronephrosis, hepatomegaly, inferior vena cava obstruction, or when the superior mesenteric artery compresses the left renal vein (nutcracker syndrome) between itself and the aorta.123 These varicoceles do not change with patient position. Sonographically varicoceles consist of multiple anechoic tubular structures around the epididymis (Fig. 36) that increase in size in the upright position and with a Valsalva maneuver. Given the slow flow in these veins, a high-frequency transducer and duplex and CFD optimized for lowflow velocities should be used, which confirm a venous flow pattern with phasic variation.124 Tasci et al further adds that retrograde flow toward the testes during Valsalva should be the main criterion for diagnosis of varicocele, as well as venous flow directed to the heart but changing direction during normal breathing.125 Grayscale imaging may demonstrate flow, seen as low-level internal echoes, and these veins will compress with manual pressure, unlike other cystic masses associated with the epididymis. Varicoceles may rarely be intratesticular (Fig. 37), within the mediastinum testis or in a subcapsular location, and are usually associated with ipsilateral extratesticular varicoceles.126,127 Patients may experience testicular pain due to stretching of the tunica vaginalis. The diagnosis can be made by identifying intratesticular veins with retrograde flow on CFD spontaneously or during Valsalva,127 which is important to perform as up to 50% will not show flow spontaneously due to slow flow.126

Scrotal Hernia An indirect inguinal hernia may contain any combination of small bowel, large bowel, omentum, or fat and the diagnosis is usually a clinical one. In equivocal cases, ultrasound can be useful and the presence of bowel in the scrotum can be deduced if valvulae conniventes, haustra, or peristalsis is seen (Fig. 38). If omental fat is the sole constituent of the hernia, an echogenic “mass” will be visualized. Similar to the clinical evaluation, ultrasound examination is best performed with the patient standing and performing a Valsalva maneuver. The scrotum along with the inguinal canal should be evalu-

Figure 38 Inguino-scrotal hernia. Transverse scans of (A) the right inguinal canal and (B) right scrotum demonstrate an inguino-scrotal hernia containing omental fat (O). A hydrocele is present (H).

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246 ated to demonstrate the extension of herniated bowel loops and or omentum through the inguinal canal. Postoperative ultrasound has been described after orchiectomy and inguinal hernia repair to identify both normal expected findings and potential complications.128,129 After orchiectomy, ultrasound identifies the normal postorchiectomy space and assesses for hematoma, recurrent neoplasm, and location of testicular prosthesis, if placed.128 After inguinal hernia repair, use is limited to symptomatic patients to evaluate for complications such as hematoma, seroma, protrusion of mesh, or bowel entrapment.129

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