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Objectives

Introduction

Embryology of male development

Anatomy and Physiology of Scrotal Imaging

Ultrasound of the Testis

Ultrasound Pathology of the Scrotum and Testis

Epididymitis

Conclusions

Summary Points

References

Bottom

Objectives:

Upon completion the reader will be able to:

• State the rationale for ultrasound image of the testis when traumatic ischemia is suspected.
• Discuss the development of male vs. female gonads as influenced by “X” or “Y” chromosome.
• List the anatomical parts of the male reproductive system and briefly discuss each parts function.
• State the origin of the testicular arteries and discuss their distribution to the testes.
• Discuss the importance of the testicles descending through the inguinal canal in the embryo.
• Discuss why cryptorchidism is considered a pathological condition with long term effects.
• Discuss the incidence of testicular cancer and the importance of ultrasound imaging for painless lumps or swelling of the scrotum.
• Discuss the importance of ultrasound imaging and blood markers to correlate diagnosis and management of testicular cancer.
• State the contents of the spermatic cord and its relationship to sperm production.
• Discuss the following noncancerous disorders of the testis: hydrocele, pyelocele, varicocele, spermatocele, epididymitis, scrotal pearl, and varicocele.
• State the importance of using color Doppler and pulsed wave Doppler to indicate the waveform of vessels in the testes.
• Discuss blood markers used to detect and manage testicular cancer.
• Discuss the sonographic appearance of non-cancerous and cancerous lesions of the testis.

Introduction

The testes have two main functions of spermatogenesis (an endocrine function), and male hormone (androgen) secretion, its exocrine function. Both functions are dependent on a good blood supply and healthy tissues. Ischemia of only 1-3 hours, for example, results in decreased spermatogenesis and irreversible changes occur in only 6-8 hours. This makes twisting of the testis due to trauma a surgical emergency. Understanding the importance of male reproduction system abnormalities is also important considering that testicular cancer is the most commonly occurring malignancy in men between the ages of fifteen and thirty-five. The incidence for mixed germ cell tumors alone is two to three cases per 100,000 males per year. Testicular cancer makes up about 1 percent of all cancers in men in the United States. About 8,000 new cases are discovered annually and approximately 390 men die from testicular cancer each year. Testicular cancer most often occurs in white males between ages 20 and 39. This disease is particularly hard on males emotionally because of the young age of its victims, and is the most common cancer in males between ages 15 and 35. For unknown reasons the rate of occurrence has doubled in white males over the last decade. A racial difference does exist in that black males are not as frequently affected, and white males are 5 times more likely to get testicular cancer than black males. The reason for difference is yet unknown. Risk factors for testicular cancer include: Cryptorchidism, prior testicular cancer, age, race, and some occupations. When the testicles do not descend from the abdomen to the scrotum before birth the condition is called cryptorchidism. The risk of developing testicular cancer is increased by a factor of 10-20 with cryptorchism. About 10% of testicular cancers seem to have a genetic basis, so a father or sibling having testicular cancer should be an early warning to screen other males of the family. Klinefelter's Syndrome, a condition of a male having an extra X chromosome can be a cause of sterility, abnormal testicular development, and risk of developing germ cell tumors. Pesticide workers, leather workers, miners, and oil workers have slightly increased risk as do persons with human immunodeficiency virus (HIV). It is a myth that vasectomy is a cause of testicular cancer in males.

Males have little knowledge of testicular self exam, making this a poorly practiced screening tool at best. Many of these cancers present as painless masses so symptoms do not reach clinical significance early in the disease. Furthermore, many laypersons are not aware that ultrasound and blood markers can be used to detect disease and manage treatments. This radiology continuing education article is written to increase public awareness, and awareness among all radiographers and sonographers of the diagnostic potential of ultrasound in diagnosing testicular disease.

Embryology of male development

The male reproductive system is generally divided into four distinct functional parts. These parts are embryological and functionally distinct. They are the testes, two-paired system of ducts, several exocrine glands, and the penis for copulation. The genital system for humans is directly due to sperm genetic compliment determined at conception. Females receive an X chromosome at fertilization and the male receives a Y chromosome. During gestation the early stages of genital development are similar and are referred to as the indifferent stage of sexual development. About the seventh week of gestation gender morphological characteristics begin to develop. Notwithstanding, at this early stage gender is not differentiated using ultrasound. The early stages of male gonad development are dependent on the strong testis forming effect of the Y chromosome. The presence of the Y chromosome is responsible for the development of the testes. In the absence of either the Y or X chromosome will cause the fetus to be female. Female gendering is not effected by the presence or absence of the gene complement X chromosome. In other words, the absence of Y produces the female gender without hormonal influence. Testes development depends on androgen effects and particularly testosterone. The development of the tunica albuginea is the first embryonic diagnostic marker of testicular development. Once it appears other structures such as the seminiferous tubules, tubli recti, and rete testis develop. Mesenchyme (undifferentiated cells) surrounding the seminiferous tubules becomes Leydig cell that secrete testosterone. At this point male differentiation of the male reproductive duct system begins, which requires suppression of female development. Sometimes ultrasound can reveal the gender of the fetus, but only after about the 18 to 20th week. Of course the fetus has to be in a good position for viewing the external genital area.

The developing testes secrete three important hormones: testosterone, genital duct inducer, and suppressor substances of the paramesonephric ducts. Ok, so this may be a bit confusing as to why we are discussing this. The point is this; male reproductive system requires hormonal control and suppression of female development. Female development is not controlled by hormones and requires no suppression of male development. This is because in the indifferent stage (first seven weeks) the embryo has both pairs of sex ducts. The mesonephric ducts (also called wolffian ducts), which is the male duct system, and the paramesonephric, ducts (also called mullerian ducts) that form the female reproductive ducts are present. So the newly developing testes produce testosterone to promote mesonephric duct development, or the male reproductive system. Testosterone also suppressed paramesonephric development, ending female reproductive system development in the male embryo.

Anatomy and Physiology of Scrotal Imaging

The male gonads are called the testes. These are paired organs that lie within the scrotal sac and are responsible for producing spermatozoa, the male gametes, and male hormones. The scrotum contains the two testis, the epididymides, part of the two ductus deferens, and some residual embryonic tissues surrounded by the visceral tunica vaginalis. The scrotal sac also contains the tunica albuginea and the dartos muscle, and a portion of the cremaster muscles within the spermatic cord. Each testicle has a duct system to convey spermatozoa, which consists of the proximal ductuli efferentes, epididymis, ductus deferens and ejaculatory ducts. The duct system is important in that it stores spermatozoa, and release them into the urethra during copulation. Spermatozoa require a fluid environment to facilitate movement through the duct system as they self propel in the female reproductive system to reach an ovum (female gamete). Three of the five glands of the male reproductive system supply the liquid moiety, which lubricates sperm, and support their nutritional energy need. These glands are the two seminal vesicles and the prostate glands. They are exocrine glands having ducts through which to secrete their products. Two accessory glands, the bulbo-urethral glands (also called Cowper’s glands), add a liquid substance that prepares the urethra to transport semen.

The right and left testicular arteries are the main blood supply to the testes. They arise from the aorta just below the renal arteries. They pass into the inguinal canal within the spermatic cord. Each testicular artery pierces the tunica abuginea along the posterosuperior testis to supply the testes, iliac lymph nodes, a portion of each ureter, and a portion of the cremaster muscle. The cremasteric artery accompanies the spermatic cord and supplies it. The cremaster muscle is also supplied by it. The differential and cremasteric arteries anastomose with the testicular artery.

This highly schematic drawing demonstrates some parts of the male reproductive system. Demonstrated are the testis, epididymis, vas deferens, seminal vesicles, and urethra. The relationship of the testes and vas deferens to the prostate gland and urinary bladder is also demonstrated.

Testis and Accessory Organs

The adult testes are paired reproductive organs weighing about 10-14 grams each and measuring about 4 cm in length and 2.5 cm in diameter. Each embryonic testis must descend from its posterior abdomen location through the inguinal canals located in the anterior abdomen. The testes begin their migration to the scrotum at about the twenty-eighth week lasting 2 or 3 days. About week 32 the testes are fully descended into the scrotum in 97 percent of males and shortly after birth for the remainder three percent. For the 3 percent of full-term males who may have an undescended testis the testis should complete migration in the first year post gestation. Cryptorchidism, the medical term for undescended testis, is a pathological condition in newborns and requires medical or surgical attention when it persists. If both testes are undescended spermatogenesis fails and the individual will be sterile. Left undiscovered and untreated there is a high association of undescended testis with testicular cancer later in life. It is estimated that there is a 10 to 40 times’ greater risk of malignant tumor with cryptorchidism. The higher in the abdomen the testis the greater the risk, and if both are undescended versus only one undescended. While descending through the inguinal canal each testis brings its ducts system, blood and lymphatic vessels, and nerves along with an investing layer of peritoneum. This layer of peritoneum called the processus vaginalis, which forms the inguinal canal. The primitive inguinal canal is tightly apposed around the ductus deferens enclosing it. The inguinal canal remains a weak area where herniation of the bowel is fairly common in males throughout life.

The main function of the testes is production of male gametes (spermatogenesis) and their development into motile sperm (spermiogenesis). The tunica albuginea extends into the testis partitioning it into about 250 lobules. Each lobule has 2-3 convoluted seminiferous tubules where sperm are produced. Within the packed coiled seminiferous tubules gametes in different developmental stages of can be seen on a histological thin section. The process involves reduction division of the human gene complement by a process called meiosis. Meiosis is a very efficient process producing thousands of sperm each second in healthy males. More than 100 million sperm are produced each day in normal fertile testes. From meiosis to full maturation is about 2 month. Special “nurse” cells called Sertoli cells are arranged circumferentially around the seminiferous tubules forming tight junctions that create a blood-testis barrier. This protects developing sperm from autoimmune destruction of the sperm. Sertoli cells also provide nourishment to spermatogonia and participate in their development.

Sperm (left drawing) are produced in the testis and matured in the epididymides. Over 100 million spermatozoa are produced daily in healthy individuals. Sperm are the male gametes that will fertilize an ovum (right electron micrograph).

The seminiferous tubules congregate on the mediastinum testis and are continuous with the efferent ductules that connect the testis to the head of the epididymis. Flagellums that line the interior of the rete testis help conduct spermatozoa towards the epididymis where they are stored. Spermatozoa at this stage have not acquired their tails to bring about self-motility. The epididymides are paired tubular organs described as a “comma-shaped” structure along the superior and posterolateral surface of each testicle. Uncoiled it is about twenty feet long; its named parts are the head, body, and tail. Spermatozoa enter the head of the epididymis through the rete testes. They are developed and stored in the body of the epididymis where they mature before exiting the tail, which is continuous with the ductus deferens. As we have stated, the ductus deferens lies within the spermatic cord. Its function is to conduct spermatozoa from the epididymis to the urethra.

We should distinguish between the testis and the scrotum. The scrotum is the sac suspended from the posterior base of the penis. The testes lie within the scrotum and are protected by it. The scrotum regulates the position of the testes to the body a function that regulates the temperature of the testis. Spermatogenesis is affected by temperature and is involuntarily controlled by the dartos and cremasteric muscles. The dartos muscle is a smooth muscle layer within the subcutaneous tissues of the scrotum. The optimal temperature for spermatogenesis is slightly cooler than internal body temperature, ideally about 96 degrees Fahrenheit. When the temperature of the testes falls below ideal for spermatogenesis the dartos muscle contracts decreasing surface area of the scrotum available to release heat. This can be seen as a wrinkled appearance of the scrotum. When the temperature of the testes is higher than core body temperature, the dartos muscle relaxes to increase the surface area of the skin available to release heat. The cremasteric muscle connected to the testis from within the spermatic cord and regulates the temperature of the testis by lower and raising it relative to the pelvis. The scrotum is subdivided into two longitudinal separate compartments by fibrous tissue called the scrotal septum. It is most apparent along the median ridge called the scrotal raphe.

The scrotum is divided into two separate compartments by the septal raphe (SR). Compartmentalization prevents infections on one side from passing to the opposite testicle. In most cases pathology such as a hydrocele will only affect one side of the testes because of this anatomical separation.

Surrounding the testis is an encapsulating layer of peritoneum called the tunica albuginea. The tunica albuginea is a thick fibrous connective tissue, which is white on dissection hence its name. Posteriorly, it is continuous with the septa that divide the testis into about 250 lobules. The testes rest in the scrotal sac supported by the tunica vaginalis, which contains a thin film of serous fluid between its layers. Two histological layers are seen composing the tunica vaginalis. The layer of the tunica vaginalis that surrounds the testicle is called the parietal layer. This is separated from the outer parietal layer by serous fluid filled cavity surrounding each testis. This reduces friction caused by movement of the scrotum. The tunica vaginalis is attached to the posterior wall of the testis preventing each testis from rotation within the scrotum. A torn tunica vaginalis or improperly developed fixation of the tunica vaginalis can result in torsion of the testis.

As the testes descend the abdomen it becomes surrounded by a serous cavity that pushes the visceral layer of the tunica vaginalis against the tunica albuginea and testis. The outer layer of the newly formed cavity becomes the parietal layer of the tunica vaginalis. Migration of the testes is through the inguinal canal into the scrotal sac.

This drawing demonstrates the histological structure of the testis. The visceral tunica vaginalis surrounds the testis. The tunica vaginalis is a fluid filled sac surrounding the testis. The seminiferous tubules are also demonstrated; they produce sperm through a process called spermatogenesis. The rete testis and epididymis are also shown in the anatomical relationships to the testis.

Within the seminiferous tubules spermatozoa are produced. This is where gametogenesis takes place through a process of meiosis. This process is unique to germ cells that reduce the genetic complement of the spermatozoa to haploid. Germ cells called spermatogonia produce haploid gametes through meiotic divisions. Meiosis results in the production of four haploid gametes called spermatid, which takes about three weeks in males. These gametes are subsequently developed in a process called spermiogenesis (lasting about 5 weeks) in which spermatids become motile. Within the seminiferous tubules gametes can be found in different stages of spermatogenesis and spermiogenesis. The rete testis (a.k.a. mediastinum testis) propels maturing sperm into the to the epididymis where they acquire their tails for full motility.

Approximately 12 ducts called the ductus efferentes conduct spermatozoa from the rete testes to the head of the epididymis. Because the spermatozoa still have not acquired their tails and therefore are not mobile the pathway is lined with cilia and flagella to brush them distally into the epididymis. The epididymis is a long comma shaped tubular structure arising from the posterolateral aspect of the testis and runs along the testes length. It consists of head that lies somewhat on the superior surface of the testes. The head of the epididymis receives spermatozoa from the siminiferous tubules. The parts of the epididymis are the proximal head, the body (consisting of many convoluted ducts where spermatids are stored), and the tail, which is continuous with the ductus deferens. The ductus deferens conducts sperms to the ejaculatory duct where they are expelled into the urethra during copulation.

The spermatic cord is a term referring to the covering that encloses those structures that pass through the inguinal ring with the testes during their descent. These structures are: the ductus deferens, testicular artery, cremasteric artery, lymph vessels, veins, artery of the ductus deferens, and remnants of the processus vaginalis. These structures can present symptoms of torsion when the cord is tangled or twisted. The spermatic cord suspends the testicles within the scrotum; it contains many structures of the male reproductive system. Structures found within the spermatic cord include the ductus deferens, testicular artery, artery of the ductus deferens, testicular artery, cremasteric artery, pampiniform plexus, sympathetic and parasympathetic nerves, motor nerves, and lymphatic vessels. The testicular artery provides the main supply of blood to the testicles and epididymis, whereas its own artery supplies the ductus deferens. The cremasteric artery joins the testicular artery just before it enters the testis, but first it supplies the cremaster muscle and coverings of the spermatic cord.

About 12 veins drain the testicles by forming an anastomotic network called the pampiniform plexus. The plexus is found along the posterior surface of the testicles. It is the major portion of the spermatic cord forming a spiraling vine-like plexus covering the ductus deferens and arteries within the cord. It terminates in the testicular vein. These veins can become blocked causing a painful varicocele of the testes.

Ultrasound of the Testis

Testicular ultrasound exam is the primary imaging modality used to detect and diagnose scrotal and testicular abnormalities. The testes are often imaged when a patient complains of testicular pain or scrotal swelling. The physician or patient may feel a lump in the scrotum or trauma involving the testicles is also reasons to perform ultrasound imaging. The use of high frequency transducers can detect intrascrotal mass with nearly 100 percent accuracy. Besides, the scan can demonstrate most parts of the male reproductive system including the testicles, mediastinum of the testes, rete testes, epididymis, prostate gland, and testicular blood flow. Conditions like inflammation of the scrotum, testicular and spermatic cord torsion, undescended testis, and abnormal blood vessels can be accurately demonstrated with ultrasound. Masses within the scrotum can be demonstrated with ultrasound. Generally a mass found within the scrotum but outside the testicle will be non-cancerous or benign, whereas those inside the testicles are with few exceptions cancerous.

Knowing the normal texture of the testes is important to the sonographer. The normal testis appears homogenous on ultrasound with an echo texture similar to the thyroid gland. The normal testis appears encapsulated owing this presentation to the hypoechoic ring, which is the tunica vaginalis. The visceral layer of the tunica vaginalis is seen apposed against the testis, separated from the parietal tunica vaginalis by a thin serous liquid. The tunica albuginea is a dense white covering of the testis; the visceral layer of the tunica vaginalis covers the tunica albuginea. The tunica vaginalis can be seen on ultrasound as a dense hypoechoic band surrounding the testis

This ultrasound image through the middle portion of a testis demonstrates the homogenous appearance of the testis. Note the thin hypoechoic ring of fibrous tissue surrounding the testis giving it an encapsulated appearance. This ring is the tunica vaginalis (white arrow), which contains a small amount of fluid between its layers (visceral and parietal tunica).

This longitudinal ultrasound image of the right testicle (left image) demonstrates the homogenous presentation of the normal testis. Again note the capsulated appearance of the testis within the scrotum. The texture of the testis is similar to the thyroid gland (right image).

In order to make an ultrasound diagnosis the anatomy of the testis and scrotum must be demonstrated. Ultrasound is especially valued for its ability to demonstrate extratesticular from intratesticular masses, and inhomogeneity within the testis. Normal testis is homogenous so any inhomogeneous findings on ultrasound are considered abnormal until proven otherwise. Structures to be demonstrated are: the mediastinum of the testis, rete testis, head of the epididymis (body and tail with hydrocele), and testis. The mediastinum of the testis is often seen as an echogenic linear band with longitudinal imaging of the testicle. The rete testis is visualized as a hypoechoic or septated cystic area near the head of the epididymis.

This longitudinal section through the right testicle demonstrates the mediastinium testis. This is the area where nerves and blood vessels enter the testicle. Notice that it is an echogenic linear band (white arrow).

This ultrasound image taken with the transducer in the transverse plane demonstrates the rete testis. Notice the hypoechoic area at the arrow having a septated appearance, the rete testis.

If possible, the entire epididymis should be demonstrated as part of the testicular ultrasound scan. The head of the epididymis is easily visualized with ultrasound, whereas the body and tail are somewhat more difficult to see when normal in size and caliber. The body and tail is most often demonstrated when surrounded by fluid as in a hydrocele. The epididymis is distinguished from the testicle by it being isoechoic or slightly more echogenic than the testis. The echotexture looks coarse compared to the adjacent testis.

This ultrasound image shows the head of the epididymis (white arrow) next to the testis. Compared to the normal testicle the epididymis is normally isoechoic or slightly more echogenic. Notice the coarse composition of the epididymis relative to the echotexture of the testicle. The contour of the epididymis over the superior portion of the testicle can be seen on the ultrasound image on the right.

These two ultrasound images demonstrate the head of the epididymis. The head of the epididymis is coarse in appearance compared to the homogenous echotexture of the testis seen in the image on the right. The white arrow in the left image of a longitudinal view of the left epididymis points to the head.

These two ultrasound images are selections from a scan of the epididymis. Demonstrated is the body (left image) and tail (right image) of the epididymis. The coarse structure of the epididymis is due to its extremely long convoluted system of tubules that store sperm. Demonstrating the head, body, and tail of the epididymis is part of the ultrasound imaging sequence for the scrotal and testicular scan.

As we have stated, three vessels, the differential, cremasteric, and testicular arteries supply testicular blood. Doppler imaging with ultrasound is a technique for demonstrating the blood flow to the testis and epididymis. Maximum effectiveness of Doppler imaging of the testis for ischemia is achieved when images are acquired at early suspicion of ischemia. The effectiveness diminishes as reactive scrotal inflammation occurs in conditions like torsion. It is important for the sonographer to know the appearance of a normal Doppler waveform for blood flow to the testicles. The normal arterial Doppler waveform will have a low-impedance for the testicular artery, and a large amount of end diastolic flow within the artery. The diferential and cremasteric arteries are found within the spermatic cord, and should show a high resistance waveform and an absence of diastolic flow.

These two transverse ultrasound images demonstrate the normal blood flow through the left testicle. The left ultrasound image shows an area through the mid testicle without color Doppler; the right image shows blood flow towards the transducer (red) and flow away from the transducer (blue).

The Doppler waveform for individual vessels can also be taken, especially when varicose veins are seen on the scan. Also waveform imaging can help determine hyperemic conditions that occur with inflammatory changes. Color Doppler (CD) is an imaging technique that allows the sonographer to demonstrate blood flow images in color placed over real time B-mode images. Red is allocated for flow towards the transducer and blue is allocated for blood flow away from the transducer. To measure what type of vessel is being demonstrated pulsed wave Doppler (PWD) can be used.

These two ultrasound images demonstrate a normal blood flow pattern in the testicle. The left is a longitudinal image and the right is a transverse image through the right testicle of the same patient. Compare this waveform with later images of pathologies of the testis for greater appreciation of what is being demonstrated.

Pulsed wave Doppler technique can be used to determine whether a vessel is arterial or venous by observing the waveform pattern shows the signal as being either above or below baseline. High resistance shows high systolic peak and low diastolic flow. Low resistance shows a double or biphasic systolic flow and high diastolic flow.

These two ultrasound images demonstrate waveforms seen with color Doppler and pulsed wave Doppler. The pulse wave signal seen of the right testicle (left picture) shows a vessel with flow away from the transducer (white arrow). On the right is an ultrasound image showing Doppler signal in a vessel in the left testicle having blood flow towards the transducer.

Ultrasound Pathology of the Scrotum and Testis

Scanning the scrotum and testicles requires the sonographer to be knowledgeable of different normal findings and pathology. Among the findings the technologist should be astute towards demonstrating are: hydrocele, hematocele and pyocele, spermatocele, epididymal cyst, epididymitis, varicocele, torsion, and scrotal pearls. There are other pathologies of the testis and scrotum; however, we will discuss these because they can be demonstrated and therefore diagnosed using ultrasound.

A hydrocele is a collection of fluid in the tunica vaginalis. It is a common cause of painless scrotal enlargement. Serous fluid may collect in the tunica vaginalis from many conditions that include infection, congestive heart failure, systemic edema, renal disease, testicular neoplasm, injury, idiopathic, or failure of the processus vaginalis to completely close at birth. A collection of fluid anywhere in the processus vaginalis after birth is considered a hydrocele. The fluid in a hydrocele at birth is usually from the peritoneal cavity and will absorb within a year. Injury or inflammation of the epididymis can also cause hydrocele in children and adults. The scrotal sac can enlarge considerable and be mistaken by the patient for enlargement of the testicles. A simple flashlight test in which light is used to trans-illuminate the scrotum will reveal a fluid filled sac with normal sized opaque testis. The ultrasound scan usually shows a hydrocele as a completely anechoic fluid. They are best seen from their lateral and anterior locations.

The ultrasound image on the left demonstrates a normal tunica vaginalis surrounding the testis. On the right, the left testis is surrounded by a hydrocele. Notice the parietal layer of the tunica vaginalis apposed to the testis and the large fluid filled space and parietal layer. This is a large hydrocele, which is only partially demonstrated on this view.

These two longitudinal images of the testis and scrotum demonstrate an extensive accumulation of fluid. The hydrocele is completely anechoic, which is how hydroceles appear on ultrasound images.

Hydroceles can be very large fluid collections that make it difficult for the physician to palpate the testis. Ultrasound is used to localize the testis so that aspiration of the hydrocele can be performed safely without puncture of the testis.

Hydroceles are clear serous fluid and therefore anechoic. Blood in the tunica vaginalis is called a hematocele. This is caused by direct trauma to the testis or torsion leading to hemorrhagic suffusion, or invasion by tumor causing a hydrohematocele. A pyelocele is pus in the tunica vaginalis. Blood and pus within the scrotal sac is frequently accompanied with pain. Elephantiasis, a disease causing lymphatic obstruction can cause lymphatic fluid to accumulate in the tunica vaginalis (chylocele). On ultrasound pyelocele and hematocele contain internal septations and fluid loculations. To remove fluid from a hydrocele a surgical procedure called an aspiration is performed. A trocar and canula are inserted into the scrotal sac and fluid is removed. A large hydrocele can compress the testicle. When the clinical picture is such that the physician cannot palpate the testicle ultrasound is used to locate the testicle and measure its size, as well as assess blood flow in the testicle before draining.

A spermatocele is a cystic collection of semen or blood in the spermatic cord. In spermatocele one or more of the ducts in the head of the epididymis becomes dilated forming a retention cyst. A spermatocele is usually asymptomatic but can be found if the individual performs routine testicular self-examination, or by a physician. Ultrasound can detect a spermatocele as a cystic dilation or mass at the head of the epididymis, and septation and debris is commonly seen.

The ultrasound image on the left is a transverse view of large spermatocele. The longitudinal ultrasound image on the right shows the spermatocele. Sometimes a spermatocele is so large that the testis is displaced. The sonographer must look closely at the fluid within the spermatocele to identify any debris. Spermatoceles range in size from 0.2 cm to over 9 cm.

Epididymal cysts are uncommonly rare and are incidental findings on ultrasound. They cannot be differentiated from spermatocele on ultrasound so aspiration of fluid is the best diagnostic criterion following ultrasound. Aspiration of the cyst removes a clear serous liquid if the cyst is epididymal, and a creamy fluid if the cyst is from a spermatocele.

These two ultrasound images, left is a transverse section through the right epididymis, and right-a longitudinal section through the right epididymis demonstrates a large cyst. These are uncommon benign findings on ultrasound. Although ultrasound can identify epididymal cyst the definitive diagnosis is made by examination of the aspirate, which should be clear for a cyst and creamy if it is a spermatocele.

Two types of disorders commonly seen on ultrasound that involve the blood supply to the testicles are torsion and varicocele. A twisting of the spermatic cord decreasing or completely blocking venous drainage or arterial supply to the testis causes torsion. It occurs most frequently in adolescents but can occur at any age. Traumatic injury is the primary cause and anatomical changes that allow exceptional movement of the testes. Other causes include absence of scrotal ligaments, or incompletely descended testicle, or significant atrophy. This is because of involvement of the testicular artery. Sudden onset of intense scrotal pain is the most common clinical symptom, and about 50% of patients report nausea and vomiting. On ultrasound the torsed testicle is usually enlarged and hypoechoic compared with the normal testicle and may contain echogenic areas representing hemorrhage.

Varicocele is not a cystic lesion because it involves the veins that drain the testicles. Varicocele is a medical term for varicose veins of the spermatic cord. A varicocele is caused when veins within the spermatic cord becomes excessively dilated resulting in a cystic-like varix. The primary cause is incompetent valves of the pampiniform plexus, but can also result from a blockage of the testicular veins or renal veins. Patients often describe their situation as having two testicles on one side. This condition most commonly affects the left testicle approximately 80% of the time; however, the right testicle can also suffer varicocele. The clinical picture is that the patient presents with worm-like swelling of the veins that mysteriously disappear when the person is supine and the testicles elevated. This prompts the physician to request an ultrasound to diagnose the condition. The patient may experience pain as the veins engorge or may have fertility problems that cause them to seek medical attention. Standing for long periods of time or heavy lifting may also have acerbated the problem.

The sonographic appearance of a varicocele demonstrates many anechoic structures measuring more than 2 mm. They are most often located near the head of the epididymis. Varicocele can be demonstrated with color Doppler; however, the sonographer must have the patient perform the “Valsalva maneuver.” The patient is asked to suspend inspiration and strain down, which raises the scrotal sac causing a temporary increase in testicular venous pressure and blood flow. This will cause dilated vessels to “light up” with color Doppler as the vasculature gorges with blood

Left ultrasound image demonstrates engorged veins of a varicocele using the “valsalva maneuver to increase intravenous pressure. The ultrasound image on the right demonstrates these small anechoic lesions that are generally greater than 2 mm.

Epididymitis

Epididymitis is the inflammation of the epididymis and is the most common cause of acute scrotal pain. The usual causes of epididymitis include leakage of spermatozoa from the lumen of the epididymis into its tissues, or bacterial invasion of the epididymis. Chlamydia and Neisseria gonorrhea are the most common bacterial causes stemming from a urinary tract infection. The patient may present with fever, dysuria, acute scrotal pain, and discharge. Acute epididymitis appears hypoechoic on ultrasound, and Doppler shows increased blood flow. Chronic epididymitis presents differently, it shows enlargement and areas that are affected will be hyperechoic.

These two ultrasound images demonstrate the epididymis. On the left is a transverse section through the epididymis. Notice its coarse appearance, which is a characteristic of chronic epididymitis. The ultrasound image on the right is a longitudinal section through the tail of the epididymis. Notice how large and hyperechoic the epididymis appears in these two images. This is chronic epididymitis. Acute epididymitis would be hypoechoic.

These two ultrasound color Doppler images demonstrate the blood flow to the epididymis. The image on the left is a transverse section, and the right a longitudinal section. Both images demonstrate increased blood flow to the epididymis, which is a characteristic of chronic epididymitis.

Scrotal pearls are another type of incidental findings on ultrasound. They have an unknown etiology and no clinical significance. They are simple calcifications found floating in the tunica albuginea.

These three ultrasound images demonstrate “scrotal pearls” in the tunica albuginea, or scrotal sac. These simple calcifications are incidental findings having no clinical significance.

There are three important benign intra-testicular pathologies that can be diagnosed with ultrasound. They are orchitis, testicular abscesses, and microlithiasis. Orchitis is inflammation of the testes usually related to and secondary to epididymitis. It commonly occurs because of an infection in the urinary tract (cystitis, urethritis, and genitoprostatitis) that seeds to the epididymis and testis through the lymphatics or ductus deferens. It also can result from mumps, trauma or autoimmune reaction. Different microorganisms depending on age and lifestyle statistically cause non-specific epididymitis and orchitis. Males under age 35 years contract microorganisms as sexually transmitted pathogens. Chlamydia and Neisseria are the most common causes of orchitis. Gonorrhea also causes a suppurative orchitis. Men over age 35 commonly contract orchitis due to urinary tract pathogens such as E. coli and Pseudomonas.

Testicular microlithiasis (TM) is seen on approximately 0.6% of testicular sonograms. Microlithiasis describes calcifications found inside the seminiferous tubules or testicles and is a very uncommon condition. Ultrasound shows several, small hyperechoic foci scattered throughout the testicle. These tiny punctate echogenic foci may be easy to recognize because they do not typically shadow. Microlithiasis has been associated with testicular cancer so those patients with this condition should be watched closely. Biannual ultrasound exam and regular testicular self-exam is recommended. The best study data comes from Memorial Sloan-Kettering Cancer Center, New York, NY done in the early 2000’s. The purpose of the study was to determine the prevalence of testicular microlithiasis in patients who were referred for scrotal ultrasonography and to evaluate the association between microlithiasis and cancer. The study was a retrospective review to determine the prevalence and relationship of testicular cancer, intratesticular mass, and microlithiasis. The results confirmed that intratesticular microlithiasis is highly associated with confirmed testicular cancer and testicular mass. This study and others have led the genitourinary physician’s community to recommend that when microlithiasis is discovered in the absence of a mass or cancer, annual ultrasound screening and physical examinations should be performed. The threshold for recommendation is based on the discovery of five or more microliths on at least one ultrasound image. If fewer than five microliths are seen on all ultrasound images, the recommendation is entirely arbitrary, and is a judgment call by the physician as to appropriate level of screening needed.

Above - Microliths are seen as punctate echogenic foci on ultrasound. Histologically, these are laminated calcium deposits in the seminiferous tubules. They are highly associated with risk of testicular cancer or mass.

Malignant disease can sometimes originate in the testes, and unfortunately the prognosis is poor unless it is discovered and treated while in the testes only. Ultrasound is a primary diagnostic tool for evaluating the testes and discovering pathology. Testicular cancer is a rare disease, but highly curable from an early detection viewpoint. It is the most common cancer in young men between the ages of 15 and 35. It is seen more in Caucasian men. Common symptoms seen with testicular cancer are a painless lump on a physical exam, a feeling of heaviness in the scrotum, significant shrinking or enlargement of a testicle and possible pain.

Classifications of testicular tumors vary greatly and the many different methods of classifying these tumors thrive. So to simplify matters we will use the simple clinical classifications that divide these tumors into two broad categories: seminoma and nonseminomatous germ cell tumors (NSGCT). The most common clinical manifestation of testicular tumors is painless enlargement of the testis, and therefore all testicular masses are neoplastic until proven otherwise.

We should distinguish between the pathos of seminomas and NSGCT. Testicular tumors characteristically spread through lymphatic channels first affecting retroperitoneal and para-aortic nodes. From retroperitoneal nodes it spreads to the mediastinal and subclavicular nodes. When hematogenous spread occurs the lungs are the primary organs affected. Secondary hematogenous spread may involve the liver, brain or bone. The main difference between seminoma and NSGCT is that seminomas tend to stay localized to the testis. Because they stay localized for a long time over 70% are discovered while still within the testis. Seminomas are highly radiosensitive accounting for a high cure rate of 85-95%. NSGCT is aggressive and carries a low prognosis because it is radioresistant. It is usually discovered in advanced stage II or stage III. It can grow so quickly that the testis may not have time to enlarge before it spreads. It prefers a hematogenous route of spread and this occurs early in the disease to involve the lungs and liver.

Certain serum tumor markers are elevated when there is a testicular tumor. This is because certain germ cell tumors secrete hormones and specific enzymes detectable by laboratory tests. Some of these bio-molecular markers include: human chorionic gonadotropin (HCG), alpha fetal protein (AFP), lactic dehydrogenase, placental lactogen, and placental alkaline phosphatase. The two most reliable ones are AFP and Beta-HGC. HCG is a glycoprotein secreted by newly formed embryo tissues. Early pregnancy test relies on the detection or measurement of HCG. Therefore, detection of beta-HCG in male serum is very diagnostic for certain testicular tumors. AFP is a major serum protein found in the early fetus. It is made in the fetal liver, gut, and yolk sac. It is never found in the blood of normal males at a concentration greater than 16 ng/ml, except in pathological states. So to detect it a most sensitive research lab type chemical test called an AFP-assay is needed. When these two markers are detected in the blood it is almost always associated with some type of nonseminomatous tumor. AFP and/or beta-HCG have been detected in 9% of seminomas, 44% of teratomas, 88% of embryonal carcinomas, and 86% of teratocarcinomas, and 75% of yolk sac tumors. Interesting, AFP is the only bio-marker elevated with yolk sac tumors, and beta-HCG is the only marker elevated with choriocarcinoma. Elevated AFP levels are also seen with liver carcinomas.

The reason it is important for the sonographer to understand the importance of AFP and beta-HCG is that these serum markers are used to aid in diagnosis and to measure the success of treatment. We have already discussed how these markers are used in diagnosis, but it should be understood that they are also beneficial in staging testicular tumors.

These side-by-side ultrasound images compare a normal testis (right) to a semioma (left). The normal testis appears solid, homogenous, and hypoechoic. The semioma has many hyperechoic areas within the testis.

These two longitudinal ultrasound sections through the right testicle demonstrate hyperechoic areas (left) and an increased blood flow (right), which is characteristic of a semioma.

Nonseminoma tumors arise from more mature specialized germ cells and are a more aggressive type of cancer than a seminoma. Some non seminoma tumors seen with ultrasound are choriocarcinoma, embryonal cell carcinoma, immature teratoma, and yolk sac tumor. Embryonal cell carcinoma is the second most common type of germ cell tumor. It accounts for about 25% of these tumors. The most common age at diagnosis is between 20 and 35 years. The type of cancer is usually small but can easily replace most if not nearly the entire testis without obvious enlargement. Embryonal cell carcinoma is more aggressive than semioma often invading the tunica albuginea causing distortion of the scrotal contour. Sonographically they appear hypoechoic becoming more homogenous as the tumor enlarges. The infantile form of embryonal cell carcinoma is known as yolk sac tumor, or endodermal sinus tumor. Yolk sac tumor is the most common germ cell tumor in infants.

Teratomas comprise about 10-15% of germ cell tumors. They are composed of all three germ layers, the mesoderm, ectoderm, and endoderm tissues. About a third of teratomas of the testicle will metastasize through lymphatic spread within 5 years of discovery. A teratoma is usually well defined on ultrasound, having a heterogeneous mass texture containing both cystic and solid areas. Dense echogenic foci with shadowing may be present within the mass because it may contain bone, teeth, and hair mixed tissues.

Choriocarcinoma is another type of neoplasm that occurs in males 20-30 years of age. It is the least common type of neoplasm accounting for 1-3% of germ cell tumors. However, it is the most malignant of testicular cancers killing almost all its victims within five years of diagnosis. When these tumors are small they can easily be missed with ultrasound and often require careful necropsy. These tumors can so aggressively invade blood vessels that it kills itself by cutting off its own blood supply. It can also produce a hemorrhagic mass in the testis during hematogenous spread. The low prognosis for choriocarcinoma is due to its rapid metastasis, and since these tumors are most often painless, gives no early warnings. This aggressive metastasis finding indicates that excision of the primary tumor must be as complete as possible and that adjuvant therapies must be directed both locally as well as systemically.

Mixed seminomatous tumors can behave like nonseminomatous germ cell tumors and are treated the same because of their low prognosis. Mixed tumors are combined tumors having two or more tissue types. About 40% of testicular tumors are mixed; the most common is teratoma and embryonal carcinoma. The prognosis decreases as more aggressive cancer types are present in the tumor. This is when blood tumor markers can be especially beneficial. Alpha-Fetoprotein is raised when embryonal carcinoma is present, and beta-HCG is found in over 50% of nonseminomatous tumors and some pure seminomas. Because these markers are not altogether diagnostic of cancer only, their greatest effectiveness is measuring post removal or cancer treatment.

Conclusions

Ultrasound of the testis is still the most common way to diagnose testicular cancer. Testicular cancer can be differentiated form other testicular abnormalities such as fluid surrounding the testis in nearly 100% of cases. Blood markers such as alpha-Fetoprotein, beta-HGC, LDH and others can help monitor prognosis following surgical and chemotherapeutic management of testicular cancer. The highest risk factors for testicular cancer is being a white male and males between ages 15 and 35. A CT scan is a beneficial diagnostic tool to stage cancer in regards to metastasis. The chest, abdomen, and pelvis CT scan is used in staging testicular cancer confirmed by ultrasound. Prognosis is good for pure seminoma and decreases with other types, with choriocarcinoma having the lowest prognosis.

Summary Points

• The testes have two main functions of spermatogenesis, or production of sperm (an endocrine function), and androgens male (hormonal secretion), its exocrine function.
• Trauma to the testis that may cause torsion is important because ischemia of only 1-3 hours, for example, results in decreased spermatogenesis and irreversible changes occur in only 6-8 hours.
• Testicular cancer is the most commonly occurring malignancy in men between the ages of 15 and 35. The incidence for mixed germ cell tumors alone is two to three cases per 100,000 males per year. Testicular cancer makes up about 1 percent of all cancers in men in the United States.
• The male reproductive system develops embryonically under the influence of the “Y” chromosome, testosterone, and female inhibitory substances. The mesonephric ducts (also called wolffian ducts), which is the male duct system, and the paramesonephric, ducts (also called mullerian ducts) that form the female reproductive ducts. So the newly developing testes produce testosterone to promote mesonephric duct development or the male genitalia, and suppress the mesonephric ducts (also called wolffian ducts), which is the male duct system, and the paramesonephric, ducts (also called mullerian ducts) that form the female reproductive ducts. So the newly developing testes produce testosterone to promote mesonephric duct development or the male reproductive system, and suppress paramesonephric development, which feminizes the reproduction systems development, which feminizes the reproduction system.
• Each embryonic testis must descend from its posterior abdomen location through the inguinal canals located in the anterior abdomen. The testes begin their migration to the scrotum at about the twenty-eighth week lasting 2 or 3 days. About week 32 the testes are fully descended into the scrotum in 97 percent of males and shortly after birth for the remainder three percent. For the 3 percent of full-term males who may have an undescended testis the testis should complete migration in the first year post gestation. Cryptorchidism, the medical term for undescended testis, is a pathological condition in newborns and requires medical or surgical attention when it persists.
• The risk of malignant testicular tumor with cryptorchidism is 10 to 40 times normal descended testes. The higher in the abdomen the testis the greater the risk, and if both are undescended versus only one undescended.
• The epididymides are paired organs described as a “comma-shaped” structure along the superior and posterolateral surface of each testicle. Named parts of the epididymis are the head, body, and tail.
• The process involves reduction division of the human gene complement by a process called meiosis. Meiosis is a very efficient process producing thousands of sperm each second in healthy males. More than 100 million sperm are produced each day in normal fertile testes. From the beginning of meiosis to full maturation is about 2 month.
• Knowing the normal texture of the testes is important to the sonographer. The normal testis appears homogenous on ultrasound with an echo texture similar to the thyroid gland. The normal testis appears encapsulated owing this presentation to a hypoechoic ring, which is the tunica vaginalis.
• Structures to be demonstrated are: the mediastinum of the testis, rete testis, head of the epididymis (body and tail with hydrocele), and testis. The mediastinum of the testis is often seen as an echogenic linear band with longitudinal imaging of the testicle. The rete testis is visualized as a hypoechoic or septated cystic area near the head of the epididymis.
• The epididymis is distinguished from the testicle by it being isoechoic or slightly more echogenic than the testis. The echotexture looks coarse compared to the adjacent testis.
• Doppler imaging with ultrasound is a technique for demonstrating the blood flow to the testis and epididymis. Maximum effectiveness of Doppler imaging of the testis for ischemia is achieved when images are acquired at early suspicion of ischemia. The effectiveness diminishes as reactive scrotal inflammation occurs in conditions like torsion.
• Color Doppler (CD) is an imaging technique that allows the sonographer to demonstrate blood flow images in color placed over real time B-mode images. Red is allocated for flow towards the transducer and blue is allocated for blood flow away from the transducer. To measure what type of vessel is being demonstrated pulsed wave Doppler (PWD) can be used.
• Pulsed wave Doppler technique can be used to determine whether a vessel is arterial or venous by observing the waveform pattern shows the signal as being either above or below baseline. High resistance shows high systolic peak and low diastolic flow. Low resistance shows a double or biphasic systolic flow and high diastolic flow.
• It is important for the sonographer to know the appearance of a normal Doppler waveform for blood flow to the testicles. The normal arterial Doppler waveform will have a low-impedance for the testicular artery, and a large amount of end diastolic flow within the artery. The diferential and cremasteric arteries are found within the spermatic cord, and should show a high resistance waveform and an absence of diastolic flow.
• Blood flow in the testicular artery is low resistance. Blood flow in the cremasteric artery is high resistance, and flow in the diferential artery is high resistance.
• A hydrocele is a collection of fluid in the tunica vaginalis. It is a common cause of painless scrotal enlargement. A pyelocele is pus in the tunica vaginalis. Blood and pus within the scrotal sac is frequently accompanied with pain. A collection of lymphatic fluid in the tunica vaginalis is a chylocele.
• A varicocele is caused when veins within the spermatic cord becomes excessively dilated resulting in a cystic-like varix. The primary cause is incompetent valves of the pampiniform plexus, but can also result from a blockage of the testicular veins or renal veins. Patients often describe their situation as having two testicles on one side. This condition most commonly affects the left testicle approximately 80% of the time.
• Varicocele can be demonstrated with color Doppler; however, the sonographer must have the patient perform the “Valsalva technique,” which involves suspended inspiration is used to temporary increase venous pressure.
• Epididymitis is the inflammation of the epididymis and is the most common cause of acute scrotal pain. Acute epididymitis appears hypoechoic on ultrasound, and Doppler shows increased blood flow. Chronic epididymitis presents differently, it shows enlargement and areas that are affected will be hyperechoic.
• Orchitis is inflammation of the testes usually related to and secondary to epididymitis. It commonly occurs because of an infection in the urinary tract (cystitis, urethritis, and genitoprostatitis) that seeds to the epididymis and testis through the lymphatics or ductus deferens. It also can result from mumps, trauma or autoimmune reaction.
• Testicular microlithiasis (TM) is seen on approximately 0.6% of testicular sonograms. Microlithiasis describes calcifications found inside the seminiferous tubules or testicles and is a very uncommon condition. Ultrasound shows several, small hyperechoic foci scattered through out the testicle. These tiny punctate echogenic foci may be easy to recognize because they do not typically shadow. Microlithiasis has been associated with testicular cancer so those patients with this condition should be watched closely.
• Testicular tumors characteristically spread through lymphatic channels first affecting retroperitoneal and para-aortic nodes. From retroperitoneal nodes it spreads to the mediastinal and subclavicular nodes. When hematogenous spread occurs the lungs are the primary organs affected. Secondary hematogenous spread may involve the liver, brain or bone.
• The main difference between seminoma and NSGCT is that seminomas tend to stay localized to the testis. Because the stay localized for a long time over 70% are discovered while still within the testis. Seminomas are highly radiosensitive accounting for a high cure rate of 85-95%.
• Certain serum tumor markers are elevated when there is a testicular tumor. This is because certain germ cell tumors secrete hormones and specific enzymes detectable by laboratory tests. Some of these bio-molecular markers include: human chorionic gonadotropin (HCG), alpha fetal protein (AFP), lactic dehydrogenase, placental lactogen, and placental alkaline phosphatase. The two most reliable ones are AFP and Beta-HGC.
• Choriocarcinoma is another type of neoplasm that occurs in males 20-30 years of age. It is the least common type of neoplasm accounting for 1-3% of germ cell tumors. However, it is the most malignant of testicular cancers killing almost all its victims within five years of diagnosis.
• Teratomas comprise about 10-15% of germ cell tumors. They are composed of all three germ layers, the mesoderm, ectoderm, and endoderm tissues. About a third of teratomas of the testicle will metastasize through lymphatic spread within 5 years of discovery.
• About 40% of testicular tumors are mixed; the most common mix is teratoma and embryonal carcinoma. Alpha-Fetoprotein is raised when embryonal carcinoma is present, and beta-HCG is found in over 50% of nonseminomatous tumors and some pure seminomas.

References

• Batata, M.A., Testicular Cancer in Cryptorchids, Cancer, 49:1023, 1982.
• Mostofi, F. K., and Price, E. B., Jr., Testicular Tumors, Tumors of the Male Genital System. Atlas of Tumor Pathology, 2nd ed, Washington, D.C. Armed Forces Institute of Pathology, 1973.
• Mostofi, F. K., and Sobin, L. H., International Histological Classification of Testicular Tumors (no. 16) W.H.O., 1977.
• Hargreave, T. B. Carcinoma In Situ of the Testis, Br. Med. J., 293:1389, 1986.
• Ariadne M. Bach, MD, Lucy E. Hann, MD, Orna Hadar, MD, Weiji Shi, MS, Hyok-Hee Yoo, BS, Catherine S. Giess, MD, Joel Sheinfeld, MD and Howard Thaler, PhD, Testicular Microlithiasis: What Is Its Association with Testicular Cancer? Radiology. 2001;220:70-75.
• Hobarth K, Susani M, Szabo N, Kratzik C. Incidence of testicular microlithiasis. Uroradiology 1992; 40:464-467.
• Backus ML, Mack LA, Middleton WD, King BF, Winter TC, True LD. Testicular microlithiasis: imaging appearances and pathologic correlation. Radiology 1994; 192:781-785
• Richie J., Neoplasms of the testis: Campell's Urology, 6th ed., Walsh PC et al (editors). Saunders, 1992.
• Walker, J. B., Pathology of Human Disease, Lea & Febiger, Philadellphia, PA, 1989.
• Anderson, J.E., Grant’s Atlas of Anatomy eighth edition, Williams & Wilkins, Baltimore, MD, 1983.
• Cotran, R.S., Kumar, V., Robbins, S.L., The Male Reproductive System: Robbins Pathological Basis of Disease 4th ed., W.B Saunders, 1989.
• Special thanks to Lindey Jo Clayton R.T., RDMS for organizing this presentation and in selecting appropriate ultrasound images from our archive.
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