Testicular Evaluation Using Bedside Ultrasonography

Testicular ultrasonography (also called scrotal ultrasonography) is the primary diagnostic modality for evaluation of testicular and scrotal disease. ^{[1, 2, 3, 4]} Its nonionizing nature, along with continued advances in technology, render ultrasonography the imaging modality of choice. Testicular ultrasonography is a useful noninvasive tool for both adult and pediatric patient groups. It serves as a good screening and diagnostic tool and helps dictate further management in the appropriate clinical setting. ^[5] Testicular ultrasonography has a wide range of applications, ranging from acute scrotal pain to more chronic and nonspecific symptoms. Testicular torsion is a urologic emergency and occurs primarily in males aged 10-19 years, with a prevalence of 1 in 4000. ^{[6, 5, 7]}

Scrotal and testicular masses can be broadly categorized into painful conditions, including testicular torsion, torsion of the testicular appendage, and epididymitis, and painless conditions such as hydrocele, varicocele, and testicular cancer. Testicular torsion is a urologic emergency requiring prompt surgical intervention to save the testicle, ideally within 6 hours of presentation, when the salvage rate is about 90%. ^[8]  In the clinical setting of testicular torsion, ultrasonography should not delay manual or surgical reduction. Testicular salvage rates drop dramatically after 6 hours, to about 60% at 13 hours and 50% by 24 hours. ^{[6, 9]}

Epididymitis is usually caused by infection with Chlamydia trachomatis, Neisseria gonorrhoeae, or enteric bacteria and is treated with antibiotics, analgesics, and scrotal support. Hydroceles are generally asymptomatic and are managed supportively. Varicoceles are also generally asymptomatic but may be associated with reduced fertility. Testicular cancer often presents as a unilateral, painless mass that is discovered incidentally. Ultrasonography is used to evaluate all suspicious masses, and surgical treatment is recommended for suspected cancerous masses. ^[8]

Typically, scrotal ultrasonography and testicular ultrasonography are not associated with any complications. The patient may experience pain if the testis is acutely inflamed or torqued, particularly in the setting of trauma. Sonography with a high-frequency transducer is the modality of choice for imaging the scrotum. Most intratesticular lesions are hypoechoic. Differentiation of intratesticular hypoechoic lesions such as testicular cysts, tumors, and inflammatory lesions, as well as segmental testicular infarction and testicular trauma, as either malignant or benign is important so that appropriate treatment can be provided. ^[10]

Guidelines on scrotal ultrasound examination have been published by the American Institute of Ultrasound in Medicine (in collaboration with the American College of Radiology, the Society for Pediatric Radiology, and the Society of Radiologists in Ultrasound). ^[11]  Indications include the following:

• Evaluation of scrotal pain, including but not limited to testicular trauma, ischemia/torsion, and infectious or inflammatory scrotal disease

• Evaluation of palpable inguinal, intrascrotal, or testicular masses

• Evaluation of scrotal asymmetry, swelling, or enlargement

• Evaluation of potential intrascrotal hernias

• Detection/Evaluation of varicoceles

• Evaluation of male infertility

• Follow-up of prior indeterminate scrotal ultrasound findings

• Localization of nonpalpable testes

• Detection of occult primary tumors in patients with metastatic germ cell tumors or unexplained retroperitoneal adenopathy

• Follow-up of patients with prior primary testicular neoplasms, leukemia, or lymphoma

• Evaluation of abnormalities noted on other imaging studies (including but not limited to computed tomography [CT], magnetic resonance imaging [MRI], and positron emission tomography [PET])

Three-dimensional (3D) ultrasonography offers an improved way to depict anatomy while assessing for abnormalities. Additional studies are needed to establish its role and added utility. ^[12]

Ultrasonography is often indicated in the workup of acute scrotal pain. It is particularly valuable in cases that are challenging to diagnose clinically and in patients whose conditions fail to respond to initial treatment. Ultrasonography is helpful for patients who present with chronic nonspecific symptoms, for whom a definitive diagnosis is not easily made. ^[13]  Ultrasonography has been shown to decrease the number of emergency scrotal explorations and length of hospital stay, thereby reducing the cost of management of acute scrotum. ^[14]  In animal studies of acute testicular ischemia, pulse-wave spectral Doppler ultrasonography has been shown to assess perfusion better than conventional color flow Doppler or power Doppler methods. ^{[9, 15]}

Ultrasonography is also used for evaluation of the following:

• Testicular swelling or masses ^{[1, 3, 4, 16]}

• Testicular trauma

• Infertility ^[17]

• Undescended testis (vanishing testes or impalpable testis in children ^[18] )

• Male hypogonadism ^[19]

• Testicular interventions (eg, ultrasound-guided aspiration, biopsy, epididymal ablation)

• Postvasectomy pain

Place the patient in a supine position. Take care to support the scrotum. Consider adducting the thighs or placing a towel or a sheet under the scrotum. However, propping the scrotum with a towel or a sheet can block inferior and coronal approaches to the testis. It may also redistribute physiologic amounts of fluid within the scrotal sac, making imaging of small structures (eg, appendix, testis) more challenging.

If the penis obstructs the scanning field, ask the patient to shift the penis superiorly toward the abdominal wall and to then cover it with a sheet.

For infants and young boys, the testes may need to be immobilized directly with the sonographer's finger because the testes are very small and mobile at this age. A towel can be wrapped around the patient's thighs to lend support and to relatively immobilize the scrotum. ^[20]

In terms of grading varicoceles, the diameter of the dominant vein in the upright position at the inguinal canal can be used. ^[21]

Ultrasonography of the scrotum should be performed with the patient's symptoms and privacy in mind. Make sure the drape covers the patient appropriately. ^[22]

A focused history and clinical examination should be performed prior to scrotal ultrasonography. Ultrasonographic findings should always be interpreted in the context of the patient's history and clinical examination. However, patient history and clinical examination findings often are not enough to discriminate between possible etiologies for the patient's symptoms.

Ask the patient to identify the area of maximum tenderness or the location of any palpable findings. Doing so saves time by decreasing time spent searching with ultrasound. Inflammation or obvious signs of ischemia or injury can dictate subsequent steps in assessment and management.

Technique

Wash hands and put on gloves.

Apply ultrasound gel.

Using direct contact, scan the scrotum and its contents in the following way:

• Begin with the asymptomatic side, then proceed to the affected side. If possible, obtain views that include both testes. Comparing both sides is essential for defining and characterizing abnormalities (see the image below).

  Bilateral view of the testes across the median raphe allows for direct comparison. The right testicle demonstrates decreased echogenicity and is consistent with infection (orchitis).

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• Scan each part of the testis and epididymis in both longitudinal and transverse planes (see the images below). The tail of the epididymis often is best visualized using a coronal view; obtaining this view may require the patient to temporarily assume a frog-leg position.

  Longitudinal view of the testicle.

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  Transverse view of the testicle with color flow Doppler. A hydrocele is present.

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• The video below presents a demonstration of a scrotal ultrasonographic examination.

  Scrotal evaluation. Video courtesy of Meghan Kelly Herbst, MD. Also courtesy of Yale School of Medicine, Emergency Medicine.

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• The videos below depict normal ultrasonographic findings.

  Cine loop depicting a normal testicle. Video courtesy of Meghan Kelly Herbst, MD. Also courtesy of Yale School of Medicine, Emergency Medicine.

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  Cine loop depicting a normal testicle with color flow, showing vasculature. This is a technique used to evaluate for orchitis (increased Doppler flow) or torsion (decreased Doppler flow). Video courtesy of Meghan Kelly Herbst, MD. Also courtesy of Yale School of Medicine, Emergency Medicine.

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Sequence of examination

The mnemonic TESTIC(K)AL is a practical sequence that serves as a useful guide to the scrotal and testicular ultrasound examination:

• Testis

• Epididymis

• Skin and soft tissues of scrotum

• Tunicae (vaginalis, albuginea)

• Internal blood supply

• Comparison with the other testis

• Kidney

• Appendages

• Do not Leave examination of the pampiniform plexus

Evaluation of the testes

Thoroughly interrogate each testis in both longitudinal and transverse planes. Be sure to compare with the contralateral side.

Decreased echogenicity

• Orchitis, epididymo-orchitis: Diffuse decreased echogenicity suggests orchitis; the addition of epididymal findings suggests a diagnosis of epididymo-orchitis; early in infection, the echogenicity may be isoechoic. (See the images below.)

  Transverse view of the testis and epididymis with color flow Doppler. Decreased echogenicity of the testis and swelling of the epididymis are consistent with epididymo-orchitis.

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  Longitudinal view with color flow Doppler demonstrating the head of the epididymis. The swelling and increased vascularity of the epididymis is consistent with epididymo-orchitis.

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• Testicular tumors: Focal low-echogenicity masses or nodules should raise suspicion; a complex cystic lesion within the testis may represent necrosis resulting from tumor. ^[1]

• Scrotal injury or hematoma: Hematomas may resemble tumors. (See the images below.)

  Bilateral view of the testes across the median raphe demonstrating a low-echogenicity mass on the right. This finding was in the context of trauma and represents a testicular hematoma.

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  Longitudinal view of the right testis. The surrounding edema, irregular appearance, and low echogenicity mass are all consistent with a testicular hematoma.

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  Transverse view of the right testis with power Doppler. The surrounding edema, irregular appearance, and low echogenicity mass are all consistent with a testicular hematoma.

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• Tunica albuginea: Irregular masses, in the context of trauma, may be associated with rupture of the tunica albuginea; prompt diagnosis followed by emergent surgery results in salvage of the testis in 80-90% of cases. ^[23]

• Torsion: In the subacute stage of testicular torsion, the testis may demonstrate low echogenicity. ^[9]

Increased echogenicity

• Testicular microlithiasis: Multiple small echogenic grainlike calcifications throughout the testicle are important to appreciate, as they may be associated with increased risk of cancer.

• Chronic atrophy: In the chronic stage of torsion, the testis may be small, atrophic, and echogenic.

Decreased vascularity

• Torsion: Decreased perfusion of the testis on Doppler imaging is the single most important finding to suggest the diagnosis of testicular torsion. ^[9]

Increased vascularity

• Infection: Acute infection results in inflammatory hyperemia and increased vascularity within the testis.

Comparison

• Directly comparing both testes may be the only manner in which a subtle abnormal finding (eg, mild decrease in echogenicity) can be appreciated.

Evaluation of epididymis

Transrectal and scrotal ultrasonography can be performed to find lesions in different parts of the seminal passage. Patients with acquired obstructive azoospermia have increased rates of distal seminal duct lesions and epididymal lesions, as well as increased epididymis volume. Transrectal and scrotal ultrasonography can prove reliable for revealing the location of acquired obstructive azoospermia. ^[24]

The shape of the epididymis varies from straight to C-shaped. Scan the epididymal head, body, and tail on both sides. Be sure to scan the epididymis in multiple planes (longitudinal, transverse, and coronal). The epididymis is usually isoechoic to the testis. Look carefully for the following:

• Cysts: Cysts are a common finding in the epididymal head; when found, measure cyst size in both longitudinal and transverse directions.

• Increased size: An enlarged and swollen epididymis is seen in epididymo-orchitis.

• Increased vascularity: Hyperemia with increased vascularity of the epididymis may be another finding of epididymo-orchitis.

• Imaging the tail of the epididymis is important because infection is often most apparent at this location.

Evaluation of skin, soft tissues, and tunicae

The scrotum is a cutaneous pouch with 2 lateral compartments divided by the median raphe. It is lined by the tunica vaginalis, which reflects over the exterior surface of each testicle.

Assess for swelling of skin and soft tissues; edema and hyperemia within the skin and subcutaneous tissues of the scrotal sac may be seen in infection (scrotal cellulitis) and trauma. In scrotal cellulitis, the skin and subcutaneous tissues are affected, but contents of the scrotum inside the tunica vaginalis are spared. Scrotal abscesses may result when testicular abscesses rupture through the tunica albuginea and into the scrotal sac.

Rupture, discontinuity, and irregular disruption of the tunica albuginea (the exterior capsule of the testicle) all suggest testicular rupture in the appropriate clinical setting; associated hematoma may exist within the testis or subcutaneous tissues; testicular fracture requires prompt surgical evaluation.

Fluid located between visceral and parietal layers of the tunica vaginalis is called a hydrocele. This may be idiopathic and asymptomatic. Reactive hydroceles are seen in association with infection, torsion, and trauma; infective processes can lead to complex hydroceles or pyoceles.

Fournier gangrene is a serious and life-threatening form of necrotizing scrotal cellulitis that involves the tissues of the perineum and the base of the penis. Unlike simple scrotal cellulitis, Fournier gangrene causes ischemia, so involved tissue does not have demonstrable inflammatory hyperemia; this condition may produce gas, which results in bright echoes with dirty shadowing on ultrasound.

Evaluation of appendages

Vestigial appendages are normal variants in the testis and epididymis that usually are of little significance. They typically have a thin, elongated, vermiform shape.

Torsion of the appendix testis or the appendix epididymis can present similar to spermatic cord torsion. Torsion of the testicular appendage presents with gradual onset of superior unilateral pain, is diagnosed using ultrasonography, and is treated supportively with analgesics. ^[8]

The torsed appendix appears enlarged, often with an altered echotexture due to infarction with or without hemorrhage. The testis appears normal, and a reactive hydrocele may be present.

Typically, blood flow is not demonstrated in the normal appendix testis or appendix epididymis. As such, absence of flow in a suspected torsed appendix has little diagnostic value.

Evaluation of the pampiniform plexus

The pampiniform plexus (venous drainage of the testicle) should be assessed in both planes via Doppler ultrasonography. The caliber of the vessels before and after the Valsalva maneuver is the mainstay in the diagnosis of varicocele.

A grading system categorizes varicoceles as small, medium, or large. The caliber of the largest vessel is measured at the groin while the patient is standing. Foroughi and colleagues found a relatively high correlation between varicocele grading based on clinical evaluation and findings on color Doppler ultrasonography. Grades were similar in testicular volume parameters and in semen analysis indices. The authors concluded that decision making should be guided by infertility history, testicular atrophy, and abnormal semen analysis. ^[25]

Varicoceles generally occur in the left scrotum because of the anatomic venous connection of the left testicular vein draining into the left renal vein.

Varicoceles are often asymptomatic but can present as a chronic ache or heaviness. They generally do not cause acute pain; however, due to slow flow, thrombosis can occur, and this may result in acute pain.

Depending upon the symptoms and the size of the varicocele, further ultrasound examinations may be needed. Varicoceles are associated with decreased fertility and require appropriate follow-up.

Small testicular masses are often benign. Clinical and ultrasound patterns are not accurate enough for including patients in surveillance protocols, and testis-pairing surgery combined with frozen section examination is pivotal for precluding the removal of testicles bearing benign lesions. ^[26]

Evaluation of the kidneys

If a varicocele is present, the kidneys must be assessed to rule out a renal mass as the cause of the varicocele. Renal lesions can impair drainage of testicular veins into the renal vein or the inferior vena cava; some advocate for routine assessment of both kidneys during every testicular ultrasound examination.

Advanced retroperitoneal tumors such as advanced renal cell carcinoma can invade, compress, or distort vascular anatomy, making surgical resection challenging and increasing risk to the patient. Intravascular ultrasonography is commonly used by vascular and cardiothoracic surgeons to obtain a real-time assessment of vascular invasion, compression, and aberrant anatomy. Intravascular ultrasound performed before radical, extirpative, retroperitoneal surgery involving large vessels can help in planning and performing this procedure. ^[27]

Testicular symptoms can be referred from the urinary tract (eg, kidney often cause pain that radiates down into the groin and testicles).

Multiple views (longitudinal, transverse, and coronal) of the structure of interest should be obtained and compared with the contralateral side. Each structure should be interrogated in terms of echogenicity and vascularity.

Classic exam findings of testicular torsion include a high-riding testis with swelling, tenderness, and loss of the cremasteric reflex. ^{[28, 29]}  

On POCUS, characteristic findings of testicular torsion include loss of visual color flow to the affected testicle; spectral Doppler imaging showing a high-resistance arterial pattern; heterogeneous echotexture and enlargement of the affected testis; and the whirlpool sign with visible twisting of the spermatic cord. ^{[28, 29]}  

In a meta-analysis by Mori et al of 4 studies (784 patients) with pediatric testicular torsion, the pooled sensitivity, specificity, and positive and negative likelihood ratios of point-of-care ultrasound were 98.4%, 97.2%, 34.7, and 0.017, respectively. ^[30]

In a meta-analysis of 14 academic hospitals (956 patients) regarding the use of Doppler ultrasonography (DUS) for patients who underwent surgery for suspected testicular torsion, Pinar et al found that DUS had a sensitivity of 85.2% and a specificity of 52.7%. ^[31]

Color DUS can result in false negatives, especially in the case of partial torsion when there is arterial flow but no venous flow; therefore, it is crucial to check both arterial flow and venous flow when performing DUS. ^[32]

In the acute setting, an unremarkable ultrasound with the presence of central testicular blood flow does not always exclude testicular torsion. Testicular torsion is based on a critical deficiency in testicular blood flow—not on absence of blood flow. ^[9]

When torsion is highly suspected, ultrasonography should not delay definitive treatment such as manual reduction or surgical exploration.

Testicular torsion is a serious surgical emergency of children. Prompt recognition and exclusion of other acute scrotal causes are essential for avoiding testicular loss. Surgical exploration is necessary in cases of clinical suspicion of testicular torsion, even if color flow Doppler ultrasound findings are normal. ^[33]

Doppler ultrasonography should be performed in all patients with acute scrotum. Optimize Doppler settings on the asymptomatic side first, prior to evaluating the symptomatic side. ^[9]

Color flow Doppler and power Doppler imaging are valuable tools; they are the mainstays in the diagnosis of emergent conditions such as testicular torsion. ^[9]

Color flow ultrasound and spectral Doppler ultrasound are the backbone of scrotal imaging when acute scrotal pain is evaluated. Testicular torsion is one of the most common causes of acute scrotal pain, but diagnosis can be challenging both clinically and sonographically. ^[34]

Ultrasonography can be used to facilitate a testis-sparing procedure. The amount of normal residual parenchyma visible on ultrasound is difficult to determine, as tissue is compressed during evaluation; thus, its true presence can be underestimated. ^[35]

Testicular torsion is a common urologic emergency, primarily in younger individuals. A good indicator of nonviability is an extended period since the onset of pain, along with heterogeneous changes in the testicular parenchyma. ^[36]  Surgical exploration is considered the gold standard for the diagnosis and management of testicular torsion. ^[37]

Radiomics can overcome visual limitations of the sonographer. Radiomics texture features can describe the testicular parenchyma with reliable quantitative parameters. Ultrasound texture features serve as a mirror into pituitary-gonadal homeostasis regarding reproductive function. ^[38]

Lim et al identified the whirlpool sign of the spermatic cord, the avascular nodule, and altered testicular vascularity as significant discriminators of testicular torsion. ^[39]