Transscrotal ultrasound
Sonography of a normal testis. The normal testis presents as a structure having homogeneous, medium level, granular echotexture. The mediastinum testis appears as thehyperechoic region located at the periphery of the testis as seen in this figure.[citation needed]
ICD-9-CM	88.79
OPS-301 code	3-05c

Scrotal (ortransscrotal)ultrasound is amedical ultrasound examination of thescrotum. It is used in the evaluation oftesticular pain, and can help identify solid masses.^[1]

Although the development of new imaging modalities such as computerized tomography and magnetic resonance imaging have opened a new era for medical imaging, high-resolution sonography remains as the initial imaging modality of choice for evaluation of scrotaldisease. Many of the disease processes, such as 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 theappropriate treatment. High-resolution ultrasound aids in improved characterization of some intrascrotal lesions and suggests more specific diagnoses, resulting in more appropriate treatments and the avoidance of unnecessary operation.^[2]

For any scrotal examination, thorough palpation of the scrotal contents and history takingshould precede the sonographic examination. Patients are usually examined in the supineposition with a towel draped over their thighs to support the scrotum. Warm gel shouldalways be used because cold gel can elicit a cremasteric response resulting in thickening ofthe scrotal wall; hence a thorough examination is difficult to be performed. A highresolution, near-focused, linear array transducer with a frequency of 7.5 MHz or greater isoften used because it provides increased resolutions of the scrotal contents. Images of bothscrotum and bilateral inguinal regions are obtained in both transverse and longitudinalplanes. Color Doppler and pulsed Doppler examination are subsequently performed,optimized to display low-flow velocities, to demonstrate blood flow in the testes andsurrounding scrotal structures. In evaluation of acute scrotum, the asymptomatic sideshould be scanned first to ensure that the flow parameters are set appropriately. Atransverse image including all or a portion of both testicles in the field of view is obtained toallow side-to-side comparison of their sizes, echogenicity, and vascularity. Additional viewsmay also be obtained with the patient performing Valsalva maneuver.^[3] Online calculators have been introduced to estimate testicular volume based on sonographic measurements.^[4]

The normal adult testis is an ovoid structure measuring 3 cm in anterior-posteriordimension, 2–4 cm in width, and 3–5 cm in length. The weight of each testis normally rangesfrom 12.5 to 19 g. Both the sizes and weights of the testes normally decrease with age. Atultrasound, the normal testis has a homogeneous, medium-level, granular echotexture. Thetesticle is surrounded by a dense white fibrous capsule, the tunica albuginea, which is oftennot visualized in the absence of intrascrotal fluid. However, the tunica is often seen as anechogenic structure where it invaginates into the testis to form the mediastinum testis. In the testis, the seminiferous tubules converge to form the rete testes, which islocated in the mediastinum testis. The rete testis connects to the epididymal head via theefferent ductules. The epididymis is located posterolateral to the testis and measures 6–7 cmin length. At sonography, the epididymis is normally iso- or slightly hyperechoic to thenormal testis and its echo texture may be coarser. The head is the largest and most easilyidentified portion of the epididymis. It is located superolateral to the upper pole of thetesticle and is often seen on paramedian views of the testis. The normal epididymalbody and tail are smaller and more variable in position.^{[citation needed]}

The testis obtains its blood supply from the deferential, cremasteric and testicular arteries.The right and left testicular arteries, branches of the abdominal aorta, arise just distal to therenal arteries, provide the primary vascular supply to the testes. They course through theinguinal canal with the spermatic cord to the posterior superior aspect of the testis. Uponreaching the testis, the testicular artery divides into branches, which penetrate the tunicaalbuginea and arborize over the surface of the testis in a layer known as tunica vasculosa.Centripetal branches arising from the capsular arteries carry blood toward the mediastinum,where they divide to form the recurrent rami that carry blood away from the mediastinuminto the testis. The deferential artery, a branch of the superior vesicle artery and thecremasteric artery, a branch of the inferior epigastric artery, supply the epididymis, vasdeferens, and peritesticular tissue.^{[citation needed]}

Four testicular appendages have been described: theappendix testis, the appendixepididymis, the vas aberrans, and the paradidymis. They are all remnants of embryonicducts. Among them, the appendix testis and the appendix epididymis are usually seen at scrotal US. The appendix testis is aMüllerian duct remnant and consists of fibrous tissue and blood vessels within an envelopeof columnar epithelium. The appendix testis is attached to the upper pole of the testis andfound in the groove between the testis and the epididymis. The appendix epididymis isattached to the head of the epididymis. The spermatic cord, which begins at the deepinguinal ring and descends vertically into the scrotum consists of vas deferens, testicularartery, cremasteric artery, deferential artery, pampiniform plexuses, genitofemoral nerve,and lymphatic vessel.^{[citation needed]}

One of the primary indications for scrotal sonography is to evaluate for the presence ofintratesticular tumor in the setting of scrotal enlargement or a palpable abnormality atphysical examination. It is well known that the presence of a solitary intratesticular solidmass is highly suspicious for malignancy. Conversely, the vast majority of extratesticularlesions are benign.^{[citation needed]}

Primary intratesticular malignancy can be divided into germ cell tumors and non–germ celltumors. Germ cell tumors are further categorized as either seminomas or nonseminomatoustumors. Other malignant testicular tumors include those of gonadal stromal origin,lymphoma, leukemia, and metastases.^[5]

Approximately 95% of malignant testicular tumors are germ cell tumors, of whichseminoma is the most common. It accounts for 35%–50% of all germ cell tumors. Seminomas occur in a slightly older age group when compared with other nonseminomatous tumor, with a peak incidence in the fourth and fifth decades. They are lessaggressive than other testicular tumors and usually confined within the tunica albuginea atpresentation. Seminomas are associated with the best prognosis of the germ cell tumorsbecause of their high sensitivity to radiation and chemotherapy.^{[citation needed]}

Seminoma is the most common tumor type in cryptorchid testes. The risk of developing aseminoma is increased in patients with cryptorchidism, even after orchiopexy. There is anincreased incidence of malignancy developing in the contralateral testis too, hencesonography is sometimes used to screen for an occult tumor in the remaining testis.On US images, seminomas are generally uniformly hypoechoic, larger tumors may be moreheterogeneous [Fig. 3]. Seminomas are usually confined by the tunica albuginea and rarelyextend to peritesticular structures. Lymphatic spread to retroperitoneal lymph nodes andhematogenous metastases to lung, brain, or both are evident in about 25% of patients at thetime of presentation.^{[citation needed]}

Nonseminomatous germ cell tumors most often affect men in their third decades of life.Histologically, the presence of any nonseminomatous cell types in a testicular germ celltumor classifies it as a nonseminomatous tumor, even if most of the tumor cells belong toseminoma. These subtypes include yolk sac tumor, embryonal cell carcinoma, teratocarcinoma,teratoma, and choriocarcinoma. Clinically nonsemionatous tumors usually present as mixedgerm cell tumors with various cell types and in different proportions.

Embryonal cell carcinoma

Embryonal cell carcinomas, a more aggressive tumor thanseminoma usually occurs in men in their 30s. Although it is the second most commontesticular tumor after seminoma, pure embryonal cell carcinoma is rare and constitutes onlyabout 3 percent of the nonseminomatous germ cell tumors. Most of the cases occur incombination with other cell types.At ultrasound, embryonal cell carcinomas are predominantly hypoechoic lesions with ill-defined margins and an inhomogeneous echotexture. Echogenic foci due to hemorrhage,calcification, or fibrosis are commonly seen. Twenty percent of embryonal cell carcinomashave cystic components. The tumor may invade into the tunica albuginearesulting in contour distortion of the testis [Fig. 4].^{[citation needed]}

Yolk sac tumor
Yolk sac tumors also known asendodermal sinus tumors account for 80%of childhood testicular tumors, with most cases occurring before the age of 2 years. Alpha-fetoprotein is normallyelevated in greater than 90% of patients with yolk sac tumor (Woodward et al., 2002, as citedin Ulbright et al., 1999). In its pure form, yolk sac tumor is rare in adults; however yolk sacelements are frequently seen in tumors with mixed histologic features in adults and thusindicate poor prognosis. The US appearance of yolk sac tumor is usually nonspecific andconsists of inhomogeneous mass that may contain echogenic foci secondary to hemorrhage.Choriocarcinoma --- Choriocarcinoma is a highly malignant testicular tumor that usuallydevelops in the 2nd and 3rd decades of life. Pure choriocarcinomas are rare and representonly less than 1 percent of all testicular tumors. Choriocarcinomasare composed of both cytotrophoblasts and syncytiotrophoblasts, with the latter responsiblefor the clinical elevation of human chorionic gonadotrophic hormone levels. As microscopicvascular invasion is common in choriocarcinoma, hematogeneous metastasis, especially tothe lungs is common. Manychoriocarcinomas show extensive hemorrhagic necrosis in the central portion of the tumor;this appears as mixed cystic and solid components at ultrasound.^{[citation needed]}

TeratomaAlthough teratoma is the second most common testicular tumor in children, itaffects all age groups. Mature teratoma in children is often benign, but teratoma in adults,regardless of age, should be considered malignant. Teratomas are composed of all threegerm cell layers, i.e. endoderm,mesoderm andectoderm. At ultrasound, teratomasgenerally form well-circumscribed complex masses. Echogenic foci representingcalcification, cartilage, immature bone and fibrosis are commonly seen [Fig. 5]. Cysts arealso a common feature and depending on the contents of the cysts i.e. serous, mucoid orkeratinous fluid, it may present as anechoic or complex structure [Fig. 6].^{[citation needed]}

• 
  Fig. 5. Teratoma. A plaque-like calcification with acoustic shadow is seen in the testis.^{[citation needed]}
• 
  Fig. 6. Mature cystic teratoma. (a) Composite Image. Mature cystic teratoma in a 29-year-old man. Longitudinal sonography image of the right testis shows a multilocular cystic mass. (b) Mature cystic teratoma in a 6-year-old boy. Longitudinal sonography of the right testis shows a cystic mass containing calcification with no obvious acoustic shadow.^{[citation needed]}

Sex cord-stromal (gonadal stromal) tumors of the testis, account for 4 per cent of alltesticular tumors. The most common are Leydig and Sertoli cell tumors.Although the majority of these tumors are benign, these tumors can produce hormonalchanges, for example, Leydig cell tumor in a child may produce isosexual virilization. Inadult, it may have no endocrine manifestation or gynecomastia, and decrease in libido mayresult from production of estrogens. These tumors are typically small and are usuallydiscovered incidentally. They do not have any specific ultrasound appearance but appear aswell-defined hypoechoic lesions. These tumors are usually removed because they cannot bedistinguished from malignant germ cell tumors.^{[citation needed]}

Leydig cell tumors are the most common type of sex cord–stromal tumor of the testis,accounting for 1%–3% of all testicular tumors. They can be seen in any age group, they aregenerally small solid masses, but they may show cystic areas, hemorrhage, or necrosis. Their sonographic appearance isvariable and is indistinguishable from that of germ cell tumors.^{[citation needed]}

Sertoli cell tumors are less common, constituting less than 1% of testicular tumors. They areless likely than Leydig cell tumors to be hormonally active, but gynecomastia can occur. Sertoli cell tumors are typically well-circumscribed, unilateral, round to lobulated masses.^{[citation needed]}

Clinically lymphoma can manifest in one of three ways: as the primary site of involvement,or as a secondary tumor such as the initial manifestation of clinically occult disease orrecurrent disease. Although lymphomas constitute 5% of testicular tumors and are almostexclusively diffuse non-Hodgkin B-cell tumors, only less than 1% of non-Hodgkinlymphomas involve the testis.^{[citation needed]}

Patients with testicular lymphoma are usually old aged around 60 years of age, present withpainless testicular enlargement and less commonly with other systemic symptoms such asweight loss, anorexia, fever and weakness. Bilateral testicle involvements are common andoccur in 8.5% to 18% of cases. At sonography, most lymphomas are homogeneous and diffusely replace the testis [Fig. 7].However focal hypoechoic lesions can occur, hemorrhage and necrosis are rare. At times,the sonographic appearance of lymphoma is indistinguishable from that of the germ celltumors [Fig. 8], then the patient's age at presentation, symptoms, and medical history, aswell as multiplicity and bilaterality of the lesions, are all important factors in making theappropriate diagnosis.^{[citation needed]}

Primary leukemia of the testis is rare. However, due to the presence of blood-testis barrier,chemotherapeutic agents are unable to reach the testis, hence in boys with acutelymphoblastic leukemia, testicular involvement is reported in 5% to 10% of patients, withthe majority found during clinical remission. The sonographicappearance of leukemia of the testis can be quite varied, as the tumors may be unilateral orbilateral, diffuse or focal, hypoechoic or hyperechoic. These findingsare usually indistinguishable from that of the lymphoma [Fig. 9].^{[citation needed]}

• 
  Fig. 9. Leukemia. Diffuse hypoechoic infiltrative lesions are seen involving the whole testis, indistinguishable from that of the lymphoma.^{[citation needed]}

Epidermoid cysts, also known as keratocysts, are benign epithelial tumors which usually occur in the second to fourth decades and accounts for only 1–2% of all intratesticular tumors. As these tumors have a benign biological behavior and with no malignant potential,preoperative recognition of this tumor is important as this will lead to testicle preservingsurgery (enucleation) rather than unnecessary orchiectomy.Clinically, epidermoid cyst cannot be differentiated from other testicular tumors, typicallypresenting as a non-tender, palpable, solitary intratesticular mass. Tumor markers such asserum beta-human chorionic gonadotropin and alpha-feto protein are negative.The ultrasound patterns of epidermoid cysts are variable and include:

1. A mass with a target appearance, i.e. a central hypoechoic area surrounded by an

echolucent rim;

1. An echogenic mass with dense acoustic shadowing due to calcification;
2. A well-circumscribed mass with a hyperechoic rim;
3. Mixed pattern having heterogeneous echotexture and poor-defined contour and
4. An onion peel appearance consisting of alternating rings of hyperechogenicities and

hypoechogenicities.^{[citation needed]}

However, these patterns, except the latter one, may be considered as non-specific asheterogeneous echotexture and shadowing calcification can also be detected in malignanttesticular tumors. The onion peel pattern of epidermoid cyst [Fig. 10]correlates well with the pathologic finding of multiple layers of keratin debris produced bythe lining of the epidermoid cyst. This sonographic appearance should be consideredcharacteristic of an epidermoid cyst and corresponds to the natural evolution of the cyst.Absence of vascular flow is another important feature that is helpful in differentiation ofepidermoid cyst from other solid intratesticular lesions.^{[citation needed]}

Although most of the extratesticular lesions are benign, malignancy does occur; the mostcommon malignant tumors in infants and children are rhabdomyosarcomas. Other malignant tumors include liposarcoma, leiomyosarcoma, malignant fibrous histiocytoma and mesothelioma.^{[citation needed]}

Rhabdomyosarcoma is the most common tumor of the lower genitourinary tract in children inthe first two decades, it may develop anywhere in the body, and 4% occur in the paratesticularregion which carries a better outcome than lesions elsewhere in the genitourinary tract. Clinically, the patient usually presents with non-specific complaints of a unilateral, painless intrascrotal swelling not associated with fever.^{[citation needed]}

Transillumination test is positive when a hydrocele is present, often resulting in amisdiagnosis of epididymitis, which is more commonly associated with hydrocele.The ultrasound findings of paratesticular rhabdomyosarcoma are variable. It usuallypresents as an echo-poor mass [Fig. 11a] with or without hydrocele. With color Doppler sonography these tumors are generally hypervascular.^{[citation needed]}

Malignant mesothelioma is an uncommon tumor arising in body cavities lined bymesothelium. The majority of these tumors are found in the pleura, peritoneum and lessfrequently pericardium. As the tunica vaginalis is a layer of reflected peritoneum,mesothelioma can occur in the scrotal sac. Although trauma, herniorrhaphy and long termhydrocele have been considered as the predisposing factors for development of malignant mesothelioma, the only wellestablished risk factor is asbestos exposure. Patients withmalignant mesothelioma of the tunica vaginalis frequently have a progressively enlarginghydrocele and less frequently a scrotal mass, rapid re-accumulation of fluid after aspirationraises the suggestion of malignancy.^{[citation needed]}

The reported ultrasound features of mesothelioma of the tunica vaginalis testis are variable.Hydrocele, either simple or complex is present and may be associated with:^{[citation needed]}

1. multiple extratesticular papillary projections of mixed echogenicity;
2. multiple extratesticular nodular masses of increased echogenicity;
3. focal irregular thickening of the tunica vaginalis testis;
4. a simple hydrocele as the only finding and
5. A single hypoechoic mass located in the epididymal head. With color Doppler sonography, mesothelioma is hypovascular [Fig. 12].

Leiomyomas are benign neoplasms that may arise from any structure or organ containingsmooth muscle. The majority of genitourinary leiomyomas are found in the renal capsule,but this tumor has also been reported in the epididymis, spermatic cord, and tunicaalbuginea. Scrotal leiomyomas have been reported in patients from the fourth to ninthdecades of life with most presenting during the fifth decade. These tumors are generallyslow growth and asymptomatic. The sonographic features of leiomyomas have beenreported as solid hypoechoic or heterogeneous masses that may or may not containshadowing calcification. Other findings include whorl shaped configuration [Fig. 13a] of the nodule and multiple, narrow areas of shadowing not cast by calcifications [Fig. 13b], but corresponding to transition zones between the various tissue components of the mass are characteristic of leiomyoma and may helpdifferentiate it from other scrotal tumors.^{[citation needed]}

Lipoma is the most common nontesticular intrascrotal tumor. It can be divided into three typesdepending upon the site of origination and spread:^{[citation needed]}

1. Originating in the spermatic cord with spread to the scrotum;
2. Originating and developing within the cord (most common type) and
3. Originating and developing within the scrotum.

At ultrasound, lipoma is a well–defined, homogeneous, hyperechoic paratesticular lesion ofvarying size [Fig. 14]. The simple finding of an echogenic fatty mass within the inguinalcanal, while suggestive of a lipoma, should also raise a question of fat from the omentumsecondary to an inguinal hernia. However lipomas are well-defined masses, whereasherniated omentum appears to be more elongated and can be traced to the inguinal area,hence scanning along the inguinal canal as well as the scrotum is necessary to make thedifferential diagnosis. Magnetic resonance imaging and computerized tomography arehelpful in doubtful cases.^{[citation needed]}

Malignant extratesticular tumors are rare. Most of the malignant tumors are solid and havenonspecific features on ultrasonography. The majority of the malignant extratesticulartumors arise from spermatic cord with liposarcoma being the most common in adults. On gross specimen, liposarcoma is a solid, bulky lipomatous tumorwith heterogeneous architecture, often containing areas of calcification. Although the sonographic appearances of liposarcoma are variable and nonspecific, itstill provides a clue about the presence of lipomatous matrix. Echogenic areas correspondingto fat often associated with poor sound transmission and areas of heterogeneousechogenicity corresponding to nonlipomatous component are present. Someliposarcomas may also mimic the sonographic appearance of lipomas [Fig. 16] and herniasthat contain omentum, but lipomas are generally smaller and more homogeneous andhernias are elongated masses that can often be traced back to the inguinal canal. CT and MRimaging are more specific, as they can easily recognize fatty component along with othersoft tissue component more clearly than ultrasound.

• 
  Liposarcoma. A heterogeneous mass consists of an upper hyperechoic portion corresponds to lipomatous matrix and areas of hypoechogenicity corresponds to nonlipomatous component is seen.^{[citation needed]}
• 
  Fig. 16. Liposarcoma mimicking lipoma. A homogeneous hypoechoic mass presents with the same appearance of lipoma, rapid growth of this tumors grants surgical intervention with pathology proved to be well differentiated liposarcoma.^{[citation needed]}

Adenomatoid tumors are the most common tumors of the epididymis and account forapproximately 30% of all paratesticular neoplasms, second only to lipoma. They are usually unilateral, more common on the left side, and usually involve theepididymal tail. Adenomatoid tumor typically occurs in men during the third and fourthdecades of life. Patients usually present with a painless scrotal mass that is smooth, roundand well circumscribed on palpation. They are believed to be of mesothelial origin and areuniversally benign. Their sonographic appearance is that of a round-shaped, well-defined,homogeneous mass with echogenicity ranging from hypo- to iso- to hyperechoic.^{[citation needed]}

Fibrous pseudotumors, also known as fibromas are thought to be reactive, nonneoplasticlesions. They can occur at any age, about 50% of fibromas are associated with hydrocele, and30% are associated with a history of trauma or inflammation (Akbar et al., 2003). Althoughthe exact cause of this tumor is not completely understood, it is generally believed that theselesions represent a benign reactive proliferation of inflammatory and fibrous tissue, inresponse to chronic irritation.Sonographic evaluation generally shows one or more solid nodules arising from the tunicavaginalis, epididymis, spermatic cord and tunica albuginea [Fig. 18]. A hydrocele is frequentlypresent too. The nodules may appear hypoechoic or hyperechoic, depending on the amount of collagen or fibroblast present.Acoustic shadowing may occur in the absence of calcification due to the dense collagencomponent of this tumor. With color Doppler sonography, a small to moderate amount ofvascularity may be seen [Fig. 19].^{[citation needed]}

• 
  Fig. 18. Fibrous pseudotumor. A homogeneous hypoechoic nodular lesion is seen attached to the tunica associated with minimal amount of hydrocele.^{[citation needed]}
• 
  Fig. 19. Fibrous pseudotumor. With color Doppler, a little vascular flow is seen in this fibrous pseudotumor.^{[citation needed]}

Epididymitis and epididymo-orchitis are common causes of acute scrotal pain in adolescentboys and adults. At physical examination, they usually are palpable as tender and enlargedstructures. Clinically, this disease can be differentiated from torsion of the spermatic cord byelevation of the testes above the pubic symphysis. If scrotal pain decreases, it is more likelyto be due to epididymitis rather than torsion (Prehn's sign). Most cases of epididymitis aresecondary to sexually transmitted disease or retrograde bacteria infection from the urinarybladder.^[6]The infection usually begins in the epididymal tail and spreads to the epididymalbody and head. Approximately 20% to 40% of cases are associated with orchitis due todirect spread of infection into the testis.^{[citation needed]}

At ultrasound, the findings of acute epididymitis include an enlarged hypoechoic orhyperechoic (presumably secondary to hemorrhage) epididymis [Fig. 20a]. Other signs ofinflammation such as increased vascularity, reactive hydrocele, pyocele and scrotal wallthickening may also be present. Testicular involvement is confirmed by the presence oftesticular enlargement and an inhomogeneous echotexture. Hypervascularity on colorDoppler images [Fig. 20b] is a well-established diagnostic criterion and may be the onlyimaging finding of epididymo-orchitis in some men.^{[citation needed]}

• 
  Doppler ultrasound of epididymitis, seen as a substantial increase in blood flow in the left epididymis (top image), while it is normal in the right (bottom image). The thickness of the epididymis (between yellow crosses) is only slightly increased (7 mm).
• 
  Doppler ultrasound of the scrotum of the same case, in the axial plane, showing orchitis (as part of epididymo-orchitis) ashypoechogenic and slightly heterogenic left testicular tissue (right in image), with an increased blood flow. There is also swelling of peritesticular tissue.

Although the genitourinary tract is the most common site of extra-pulmonary involvementby tuberculosis, tuberculous infection of the scrotum is rare and occurs in approximately 7%of patients with tuberculosis. At theinitial stage of infection, the epididymis alone is involved. However, if appropriateantituberculous treatment is not administered promptly, the infection will spread to theipsilateral testis. The occurrence of isolated testicular tuberculosis is rare. Clinically patients with tuberculous epididymo-orchitis may present with painful or painless enlargement of the scrotum, hence they cannot be distinguished from lesions such as testicular tumor, testicular infarction and may mimic testicular torsion.^{[citation needed]}

At ultrasound, tuberculous epididymitis is characterized by an enlarged epididymis withvariable echogenicity. The presence of calcification, caseation necrosis, granulomas andfibrosis can result in heterogeneous echogenicity [Fig. 21a]. The ultrasound findings oftuberculous orchitis are as follow: (a) diffusely enlarged heterogeneously hypoechoic testis(b) diffusely enlarged homogeneously hypoechoic testis (c) nodular enlargedheterogeneously hypoechoic testis and (d) presence of multiple small hypoechoic nodules inan enlarged testis [Fig. 21b].^{[citation needed]}

Although both bacterial and tuberculous infections may involve both the epididymis andthe testes, an enlarged epididymis with heterogeneously hypoechoic pattern favors adiagnosis of tuberculosis (Muttarak and Peh, 2006, as cited in Kim et al., 1993 and Chung et al., 1997). With color Doppler ultrasound, a diffuse increased blood flow pattern is seen inbacterial epididymitis, whereas focal linear or spotty blood flow signals are seen in theperipheral zone of the affected epididymis in patients with tuberculosis.^{[citation needed]}

Fournier gangrene is a polymicrobial necrotizing fasciitis involving the perineal, perianal, or genital regions and constitutes a true surgical emergency with a potentially high mortality rate. Majorly caused by Haemolytic streptococci organisms (Staphylococcus, E.coli, Clostrdium welchii). It usually develops from a perineal or genitourinary infection but can arise followinglocal trauma with secondary infection of the wound. 40–60% of patients are being diabetic.Although the diagnosis of Fournier gangrene is often made clinically, diagnostic imaging isuseful in ambiguous cases.^{[citation needed]}The sonographic hallmark of Fournier gangrene is presence of subcutaneous gas within thethickened scrotal wall. At ultrasound, the gas appears as numerous, discrete, hyperechoicfoci with reverberation artifacts [Fig. 22]. Evidence of gas within the scrotal wall may beseen prior to clinical crepitus. The only other condition manifesting with gas at sonographicexamination is an inguinoscrotal hernia. This can be differentiated from Fournier gangreneby the presence of gas within the protruding bowel lumen and away from the scrotal wall.(Levenson et al., 2008).^{[citation needed]}

The normal testis consists of several hundred lobules, with each lobule containing severalseminiferous tubules. The seminiferous tubules of each lobule merge to form the straighttubes, which in turn converge to form the rete testis. The rete testis tubules, which lie withinthe mediastinum testis, are an anastomosing network of irregular channels with a broadlumen, which then empties into the efferent ductules to give rise to the head of theepididymis. Obstruction in the epididymis or efferent ductules may lead to cystic dilatationof the efferent ductules, which usually presents as an epididymal cyst on ultrasound.However, in the more proximal portion this could lead to the formation of an intratesticularcyst or dilatation of the tubules, so-called tubular ectasia. Factors contributing to thedevelopment of tubular ectasia include epididymitis, testicular biopsy, vasectomy or anaging process. Clinically this lesion is usually asymptomatic. Theultrasound appearance of a microcystic or multiple tubular-like lesions located at themediastinal testis [Fig. 23] and associated with an epididymal cyst in a middle-aged orelderly patient should alert the sonographer to the possibility of tubular ectasia.The differential diagnosis of a multicystic lesion in testis should include a cystic tumor,especially a cystic teratoma. A cystic teratoma is usually a palpable lesion containing bothsolid and cystic components; and the cysts are normally larger than that of tubular ectasia,which appear microcystic [Fig. 24]. Furthermore, the location of tubular ectasia in themediastinum testis is also helpful in making the differential diagnosis.^{[citation needed]}

Histologically, testicular microlithiasis refers to the scattered laminated calcium deposits inthe lumina of the seminiferous tubules. These calcifications arise from degeneration of thecells lining the seminiferous tubules. At ultrasonography, microliths appear as tiny punctateechogenic foci, which typically do not shadow. Although minor microcalcification within atestis is considered normal, the typical US appearance of testicular microlithiasis is ofmultiple nonshadowing echogenic foci measuring 2–3 mm and randomly scatteredthroughout the testicular parenchyma [Fig. 25] (Dogra et al., 2003, as cited in Janzen et al.,1992). The clinical significance of testicular microlithiasis is that it is associated withincreased risk of testicular malignancy, thus follow up of affected individuals with scrotalsonography is necessary to ensure that a testicular tumor does not develop.^{[citation needed]}

• 
  Fig. 25. Testicular microlithiasis. Multiple hyperechoic foci without acoustic shadow presenting as a starry sky appearance is seen in the testis.^{[citation needed]}

The normal testis and epididymis are anchored to the scrotal wall. If there is a lack ofdevelopment of these attachments, the testis is free to twist on its vascular pedicle. This willresult in torsion of the spermatic cord and interruption of testicular blood flow. Testiculartorsion occurs most commonly at 12 to 18 years but can occur at any age. Torsion results inswelling and edema of the testis, and as the edema increases, testicular perfusion is furtheraltered. The extent of testicular ischemia depends on the degree of torsion, which rangesfrom 180° to 720° or greater. The testicular salvage rate depends on the degree of torsion andthe duration of ischemia. A nearly 100% salvage rate exists within the first 6 hours after theonset of symptoms; a 70% rate, within 6–12 hours; and a 20% rate, within 12–24 hours. Therefore, testicular torsion is a surgical emergency and the role of ultrasound is to differentiate it from epididymitis as both diseasepresents with acute testicular pain clinically.^{[citation needed]}

There are two types of testicular torsion: extravaginal and intravaginal. Extravaginal torsionoccurs exclusively in newborns. Ultrasound findings include an enlarged heterogeneoustestis, ipsilateral hydrocele, thickened scrotal wall and absence of vascular flow in the testisand spermatic cord. The ultrasound findings of intravaginal torsion vary with the duration and the degree of rotation of the spermatic cord. Gray scale ultrasound may appear normal if the torsion just occurs. At 4–6 hoursafter onset of torsion, enlarged testis with decreased echogenicity is seen. At 24 hours afteronset, the testis appears heterogeneous due to vascular congestion, hemorrhage andinfarction. As gray scale ultrasound is often normal during early onset oftorsion, Doppler sonography is considered essential in early diagnosis of testiculartorsion. The absence of testicular flow at color and power Doppler ultrasound is considereddiagnostic of ischemia, provided that the scanner is set for detection of slow flow,the sampling box is small and the scanner is adjusted for the lowest repetition frequencyand the lowest possible threshold setting.^{[citation needed]}

Varicocele refers to abnormal dilatation of the veins of the spermatic cord due toincompetence of valve in the spermatic vein. This results in impaired blood drainage intothe spermatic vein when the patient assumes a standing position or during Valsalva'smaneuver. Varicoceles are more common on the left side due to the following reasons (a)The left testicular vein is longer; (b) the left testicular vein enters the left renal vein at a rightangle; (c) the left testicular artery in some men arches over the left renal vein, therebycompressing it; and (d) the descending colon distended with feces may compress the lefttesticular vein.^{[citation needed]}

The US appearance of varicocele consists of multiple, hypoechoic, serpiginous, tubular likestructures of varying sizes larger than 2 mm in diameter that is usually best visualizedsuperior or lateral to the testis [Fig. 27a]. Color flow and duplex Doppler US optimized forlow-flow velocities help confirm the venous flow pattern, with phasic variation andretrograde filling during a Valsalva's maneuver [Fig. 27b]. Intratesticular varicocele mayappear as a vague hypoechoic area in the testis or mimics tubular ectasia. With colorDoppler, this intratesticular hypoechoic area also showed reflux of vascular flow duringValsalva's maneuver [Fig. 28].^{[citation needed]}

Normally the testes begin its descent through the inguinal canal to the scrotum at 36 weeks’of gestation and completed at birth. Failure in the course of testes descent will result inundescended testes (Cryptorchidism).

Undescended testis is found in 4% of full-term infants but only 0.8% ofmales at the age of 1 year have true cryptorchidism. Although an undescended testis can befound anywhere along the pathway of descent from the retroperitoneum to the scrotum, theinguinal canal is the most common site for an undescended testis. Deviation of testis fromthe normal pathway of descent will result in ectopic testis that is commonly seen inpubopenile, femoral triangle and perineal regions.^{[citation needed]}

Besides infertility, undescended testes carry an increased risk of malignancy even for thenormally located contralateral testis. The risk of malignancy is estimated to be as high as 10 times the normal individual with seminoma being the most common malignancy^{[citation needed]}.

The incidence of infertility is decreased if surgical orchiopexy is carried out before the 1–3 yearsbut the risk of malignancy does not change.Because of the superficial location of the inguinal canal in children, sonography ofundescended testes should be performed with a high frequency transducer. At ultrasound,the undescended testis usually appears small, less echogenic than the contralateral normaltestis and usually located in the inguinal region [Fig. 29]. With color Doppler, the vascularityof the undescended testis is poor.^{[citation needed]}

• 
  Fig. 29. Undescended testis. (a) Normal testis in the scrotum. (b) Atrophic and decreased echogenicity of the contralateral testis of the same patient seen in the inguinal region.^{[citation needed]}

At sonography, the appendix testis usually appears as a 5 mm ovoid structure located in thegroove between the testis and the epididymis. Normally it is isoechoic to the testis but attimes it may be cystic. The appendix epididymis is of the same size as the appendix testisbut is more often pedunculated. Clinically pain may occur with torsion of either appendage.Physical examination showed a small, firm nodule is palpable on the superior aspect of thetestis and a bluish discoloration known as ‘‘blue dot’’ sign may be seen on the overlyingskin. Torsion of the appendicealtestis most frequently involved in boys aged 7–14 years (Dogra and Bhatt 2004).The sonographic features of testicular appendiceal torsion include a circular mass withvariable echogenicity located adjacent to the testis or epididymis [Fig. 30], reactivehydrocele and skin thickening of the scrotum is common, increased peripheral vascular flowmay be found around the testicular appendage on color Doppler ultrasound. Surgicalintervention is unnecessary and pain usually resolves in 2 to 3 days with an atrophied orcalcified appendages remaining.^{[citation needed]}

A scrotalhematocele is a collection ofblood in thetunica vaginalis around thetesticle.^[7] It can followtrauma (such as astraddle injury) or can be a complication of surgery. It is often accompanied bytesticular pain. It has been reported in patients withhemophilia and followingcatheterization of thefemoral artery. If the diagnosis is not clinically evident,transillumination (with a penlight against the scrotum) will show a non-translucent fluid inside the scrotum.Ultrasound imaging may also be useful in confirming the diagnosis. In severe or non-resolving cases, surgicalincision and drainage may be required. To prevent recurrence following surgical drainage, adrain may be left at the surgical site.

A striated pattern of the testicle, radiating from its mediastinum, does not have clinical importance unless there are alarming symptoms or abnormal signal onDoppler ultrasonography.^[8] It is presumed to represent fibrosis.^[8]

Ultrasound remains as the mainstay in scrotal imaging not only because of its high accuracy,excellent depiction of scrotal anatomy, low cost and wide availability, it is also useful indetermining whether a mass is intra- or extra-testicular, thus providing us useful andvaluable information to decide whether a mass is benign or malignant even thoughmalignancy does occur in extratesticular tumors and vice versa. Furthermore, ultrasound alsoprovides information essential to reach a specific diagnosis in patients with testiculartorsion, testicular appendiceal torsion and inflammation such as epididymo-orchitis, Fournier gangrene etc., thus enabling us to avoid unnecessary operation.^{[citation needed]}

• Male infertility § Ultrasonography

• Diagnostic medical imaging
• Male genital procedures
• Medical ultrasonography
• Scrotum

• All articles with unsourced statements
• Articles with unsourced statements from December 2019
• Articles with short description
• Short description is different from Wikidata
• Articles with unsourced statements from October 2018