• Discuss the sonographic characteristics of the scrotum in the normal and abnormal condition.
• Explain the clinical and sonographic findings of epididymitis and orchitis.
• Describe the sonographic appearance of torsion.
• Recognize the appearance of hydroceles and varicoceles of the scrotum.
• Identify tumors of the testicle to include clinical findings, lab values, and sonographic findings.

This program will focus on the sonographic evaluation of the scrotum and scrotal pathology. Sonography plays an important role in evaluating testicular size, differentiating between intratesticular or extratesticular abnormalities causing scrotal enlargement or a palpable mass, finding an occult (concealed) neoplasm, evaluating the condition of the testicle in cases of trauma or infection, and determining the presence or absence of a varicocele in an infertility workup. The majority of extratesticular masses are benign, but the majority of intratesticular masses are malignant. It is also important for the sonographer to describe the appearance of the mass, to determine if it is cystic or solid, well-defined or irregular.

Clinically a scrotal mass may be present or found on physical examination. Sometimes the mass is accompanied by pain as hemorrhage into the tumor can produce pain and tenderness. The clinical findings, pertinent lab data, and sonographic evaluation will be presented for the major scrotal pathologies seen by ultrasound.

A complete history should be taken or reviewed prior to the sonographic evaluation of the scrotum. The patient should be asked to lie down on the examination table. The patient is placed in the supine position, a sheet is provided for coverage. The sonographer should avoid a cold room to reduce testicular retraction and skin thickening. A small towel is placed under the scrotal sac to provide stability for the ultrasound examination. The penis is gently drawn up toward the patient’s lower abdomen and covered with a towel. Warm gel is then applied freely to the scrotal sac. To optimally visualize the scrotum, a high resolution linear array (7.5MHz or higher) is usually the ideal transducer to employ for this study.

Both testicles should be scanned completely, in both the longitudinal and transverse planes. The initial scan should evaluate both testes on the same image. This will allow the sonographer to assess the homogeneity of the testes, evaluate size, and to determine if any apparent asymmetry is present. Transverse scans of each testis are then made beginning at the most superior part of the testes and scanning inferiorly. Representative images are made at the upper, mid, and lower planes of the right and left testis. Longitudinal scans of each testis are also made to include the lateral, mid, and medial portions.

The rete testes drain from the testes into the efferent ductules which drain into the tubules that form the epididymal head. The head of the epididymis is triangular with rounded edges and its echogenicity is similar to that of the testis. It rests on the upper pole of the testis. The epididymal head and body, and the tail (if possible) should also be evaluated. The tail is small and located more posteriorly and is therefore more difficult to image. The spermatic cord area should be scanned from the inguinal canal to the scrotum. A separate image of the epididymal head in relation to the superior portion of the testicle should be obtained.

The normal testes should appear as small homogeneous ovoid structures with an echogenicity texture similar to the thyroid. The echogenic mediastinal stripe may be seen to flow through the mid section of the testis. The Doppler settings for color flow should be set for low volume, low velocity flow to optimize visualization of the small testicular arteries.

Infections: Epididymitis and Orchitis.
Epididymitis. The epididymis functions as a storage, transport, and maturation place for sperm before ejaculation. Epididymitis is a condition in which the epididymis becomes inflamed and tender.

The patient may present with fever and chills, pain in the inguinal region, and a swollen epididymis. The inflammation may spread into the testicular area (orchitis). The infection is usually unilateral. Epididymitis may be caused by a complication of infections and conditions associated with sexually transmitted disease, tuberculosis, mumps. Prostatitis, urethritis, or prolonged use of an indwelling catheter.

Epididymitis is most common between the ages of 18 and 40, but it can also be found in children. Young boys with painful urination, a previous history of urinary tract infection, abnormal bladder function, or abnormalities of the genitals are more likely to develop epididymitis.

Sonographically the acute epididymitis usually shows enlargement of the epididymal head with decreased echogenicity secondary to edema. A reactive hydrocele may be present. Color Doppler findings include an increased amount of flow in and around the epididymis. If an abscess has formed, complex cystic areas may be identified in the epididymis.

Orchitis. Once the infection has spread to the testicle, it is termed orchitis. The testicle may appear normal or enlarged in size and the echogenicity may be decreased or heterogeneous. Reactive hydroceles and skin thickening are associated with orchitis. As in many infections, there will be increased color Dopplor flow to the infected testes. Chronic orchitis appears as layers of heterogeneous disruption within the testicle. Focal orchitis may occur without involvement of the epididymis and has the same appearance as a neoplasm, although clinical symptoms such as fever and increased white blood cell count strongly would suggest an infectious process.

Trauma. A direct blow to the scrotal sac can cause significant testicular parenchymal injury or hemorrhage and can definitely alter the normal homogeneous appearance of the testicle. Hematomas in the epididymis or scrotal wall may have variable sonographic appearances. Just like hematomas in other parts of the body, their appearance may vary depending upon the age of the hematoma. At first the hematoma will be hypoechoic as the red blood cells fill the space; as the hematoma ages, its appearance becomes more echogenic as clot begins to form within the bleed.

Torsion. The testicle is attached to the scrotum at the bare area. If the bare area is small, a tiny remnant stalk of tunica vaginalis allows the testicle to be mobile. Torsion occurs when the testicle revolves one or more times on this short stalk, which obstructs blood flow to the testicle, resulting in severe pain. Torsion is more common in males under 25 years of age with a peak incidence at 13 years. Once torsion occurs, the testicle becomes congested and edematous because of the veins in the twisted cord. Pressure within the testicle then begins to build up because of the arterial obstruction which then leads to the testicular ischemia. It is important to diagnose this abnormality early because necrosis of the torsed testicle will occur within 24 hours.

Sonographically, a torsed testicle appears normal in the first four hours of torsion. Although the realtime appearance of the testes is normal, Color and pulsed-Doppler appearances are abnormal. There is an absence of flow in the testicle and the epididymis. After four hours, the torsed testicle appears enlarged and hypoechoic. The testicle may have some inhomogenous appearances as a result of hemorrhage. Other findings include enlargement of the epidiymis, a reactive hydrocele, and scrotal wall thickening.

Spermatoceles. A spermatocele is a benign cyst consisting of nonviable sperm. They are commonly located in the head of the epididymis, but have been found in the body and tail as well. Septations have been seen with the cysts. The spermatoceles may be singular or multiple.

On sonography, a spermatocele appears as a cyst, anechoic with posterior enhancement with rounded, well-defined walls. A spermatocele cannot be differentiated from a simple epididymal cyst.

Epididymal Cysts. These masses are composed of clear serous fluid, not sperm and are much less common than spermatoceles. Sonographically they present as a typical cystic type appearance with well-defined walls and good transmission.

Hydrocele

A hydrocele is a collection of fluid between the visceral and parietal layers of the tunica vaginalis. Hydroceles can be congenital, idiopathic, or acquired. Acquired hydroceles are the results of infarction, inflammation, neoplasm, or trauma.

Sonographically hydroceles may appears as anechoic fluid in the scrotal sac surrounding the testicle and epididymis. Occasionally, small particles and septations are seen within the fluid.

Varicocele

A varicocele is the abnormal dilation and tortuosity of the veins in the pampiniform plexus that run along the spermatic cord into the scrotum. The spermatic cord provides nourishment through the blood vessels and contains nerves and lymph glands as well as the vas deferens. Varicoceles are reported to be found in 15% of all males. They are found to be the cause of infertility in 30-40% of the cases. The varicoceles develop when a defective valve in the vein allows the normal one-way flow of blood to back up into the abdomen. Blood then flows from the abdomen into the scrotum where a hostile environment for sperm development is created. Most varicoceles develop slowly and do not show symptoms. Some are large and visible as twisting veins in the scrotal sac. These veins disappear when lying down and the valsalva maneuver (bear down or cough) is used to demonstrated their filling distention.

They are more common on the left side, but do also occur bilaterally. The right internal spermatic vein drains directly into the inferior vena cava, whereas the left internal spermatic vein drains into the left renal vein at a 90-degree angle. This angle prevents the formation of a valve. As a result, 85-99% of the varicoceles are left-sided and only 1% are bilateral.

Varicoceles may cause infertility because they are associated with low sperm counts and decreased mobility. Sonographically they appear as an extratesticular collection of tortuous tubular structures.

Benign Testicular Lesions

Benign testicular lesions are rare; most extratesticular lesions are benign. The anechoic lesions include testicular cysts while the complex lesions include abscess, orchitis, torsion, or tumor.

Microlithiasis

It is not uncommon to see two or three tiny calcifications in the testicle. Mutiple tiny calcifications throughout the testes have been found and are termed microlithiasis. Although microlithiasis has been seen in normal patients, it is associated with tumors, sterility, and cryptorchidism. Sonographically, microlithiasis appears as multiple echogenic non-shadowing areas throughout the testis, and these calcifications may obscure other pathologic conditions.

Sonographic characteristics

Germ Cell Tumors

This tumor classification includes seminoma, teratoma, yolk sac tumor, embryonal cell carcinoma, and choriocarcinoma. Most tumors (65%) are of one histologic type of tumor; the other tumors are mixed origin. The germ cell tumors are more common in Caucasian young adult males and is uncommon after the age of 50. The risk for this tumor is increased 4-10 fold if cryptorchidism is present. The development of germ cell tumor in one testis increases the risk of tumor in the contralateral testis.

Seminoma. The is the most common single type of primary testicular tumor (35-70%) and the most common tumor found in patients with undescended testis. The peak age of occurrence is 30-40 years of age. The serum alpha fetoprotein is usually normal and the beta HCG elevation is present in 10-15% of the cases.

On ultrasound the seminomas tend to appear more homogeneous and hypoechoic than other germ cell tumors until they become large, at which point they become heterogeneous. They are usually confined within the tunica albuginea. These tumors are very sensitive to radiation and chemotherapy. The survival rate is high at 75-85%.

Embryonal Cell Carcinoma. This is the most common component of mixed testicular tumors, comprising 15-35% of the germ cell tumors. It occurs in the pediatric group (under two years) and in the young adult group, 20-30 years. This tumor is the most aggressive testicular tumor. It metastasizes early and widely via the lymphatic and hematogenous routes. Alpha fetoprotein may or may not be elevated. On ultrasound a hypoechoic mass with areas of increased echogenicity and cystic areas representing necross and hemorrhage may be seen. Invasion of the tunica albuginea should be evaluated. The survival rate is low at 30-35%.

Teratoma. Although the frequency (4-10%) of teratomas is low, it is the second most common testicular tumor in young boys. Generally this tumor is found to be benign in the pediatric group; it may transform into malignancy in adulthood. The serum alpha fetoprotein may be elevated. On ultrasound the texure of the mass is complex with sonolucent and echogenic components. There is often metastases to the lymph nodes, bone, and liver in 30% of the patients within five years.

Choriocarcinoma. This is an uncommon form of germ cell tumor (1-3%). The peak age is the young adult male. The tumor may rapidly metastasize without evidence of chordiocarcinoma in the primary lesion. There is a high incidence of pulmonary involvement. The serum beta HCG is always elevated. On ultrasound a complex echo pattern is shown with hemorrhage, necrosis, and calcifications. The prognosis is not good.

Yolk Sac Tumor. This tumor is the most common germ cell testicular tumors of infancy and childhood. The serum alphafetoprotein is always elevated.

Metastases to Testis. Metastases to the testis is not a common occurrence. In adults metastases from the prostate > lung > kidney > GI tract, bladder, thyroid, melanoma. Metastases is more common than germ cell tumors in males over 50 years of age. In children neuroblastoma is the primary cause for metastases to the testis. Sonographically it usually appears as a solid hypoechoic mass.

Lymphoma / leukemia of Testis. Lymphoma is not very common (6-7% of all testicular tumors) although it is the most common testicular tumor in men over the age of fifty and is found bilaterally in 40% of cases. Sonographically it appears as a diffuse or focal area of decreased echogenicity.

• “A Look at Varicoceles: Part I”. http://infertility.about.com/library/weekly/aa103198.htm
• Dahnert W. Radiology Review Manual 3rd Ed., Williams & Wilkins, Baltimore, 1996.
• “Epididymitis”. http://www.gale encyclopedia of Alternative Medicine.
• Hagen-Ansert, SL. Textbook of Diagnostic Ultrasonography, 5th Ed., Mosby, St. Louis, 2001.
• Kurtz AB. Ultrasound: The Requisites, Mosby, St. Louis, 1996.
• “Male Genital Tract Pathology”. http://hsc.virginia.edu/med-ed/path/gu/testis4
• “Testicular Cancer”. http://www.merck.com/pubs/mmanual/sectionI7
• “Testicular Cancer”. http://www.cancernetwork.com/handbook/Testicular
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