DOI: 10.1148/rg.255045109
RadioGraphics 2005;25:1197-1214
© RSNA, 2005
Gray-Scale and Color Doppler Sonography of Scrotal Disorders in Children: An Update1
Celestino Aso, MD,
Goya Enríquez, MD,
Marta Fité, MD,
Nuria Torán, MD,
Carmen Piró,
Joaquim Piqueras, MD and
Javier Lucaya, MD
1 From the Departments of Pediatric Radiology (C.A., G.E., M.F., J.P., J.L.), Pathology (N.T.), and Pediatric Surgery (C.P.), Vall d’Hebron Children’s Hospital, Ps Vall d’Hebron 119–129, 08035 Barcelona, Spain. Recipient of a Certificate of Merit award for an education exhibit at the 2003 RSNA Annual Meeting. Received May 18, 2004; revision requested October 13 and received January 13, 2005; accepted January 17. All authors have no financial relationships to disclose.
Address correspondence to G.E. (e-mail: genriquez{at}vhebron.net).
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Abstract
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Ultrasonography (US) is well suited to the study of pathologic conditions of the scrotum in children. US provides excellent anatomic detail; when color Doppler and power Doppler imaging are added, testicular perfusion can be assessed. Gray-scale, color Doppler, and power Doppler US were used to study a spectrum of scrotal disorders in 750 boys aged 1 day to 17 years. The entities studied included processus vaginalis–related disorders (cryptorchidism, inguinal-scrotal hernia, and hydrocele); varicocele; acute scrotum (epididymo-orchitis, torsion of the testicular appendages, and testicular torsion); scrotal tumors; testicular microlithiasis; scrotal trauma; and systemic diseases with scrotal involvement. When combined with the results of clinical and physical examination, the information obtained with US is sufficient to enable diagnosis in most cases of scrotal disease. Moreover, color Doppler imaging is essential for differentiation between processes such as epididymo-orchitis or torsion of the testicular appendages and testicular torsion, which have similar clinical manifestations (pain, swelling, and redness) but are managed differently.
© RSNA, 2005
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LEARNING OBJECTIVES FOR TEST 1
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After reading this article and taking the test, the reader will be able to:
- Describe how to perform US of the scrotum in children.
- Identify a spectrum of scrotal disorders with US.
- Discuss the treatment of patients with acute scrotum.
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Introduction
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Gray-scale ultrasonography (US) in combination with color or power Doppler imaging is a well-accepted technique for assessing scrotal lesions and testicular perfusion (1–7). The clinical manifestations in many scrotal processes include pain, swelling, redness, and a palpable mass. US permits differentiation between lesions that require urgent surgery (testicular torsion, malignant tumors, and traumatic rupture) and those that can be managed conservatively (eg, epididymo-orchitis, torsion of the testicular appendages) (8–10).
The objective of this article is to familiarize the reader with the US features of the most common and some of the least common scrotal lesions in children. These lesions include processus vaginalis–related disorders, varicocele, acute scrotum, scrotal tumors, testicular microlithiasis, scrotal trauma, and systemic diseases with scrotal involvement. In addition, we present the scanning protocol used when examining such patients and the normal anatomy of the scrotum at US.
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Clinical Experience
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Patients
This article is based on our experience with sonographic study of 750 boys with scrotal anomalies. The patients were aged 1 day to 17 years and were seen in the Department of Pediatric Radiology at our institution during the period 1993–2003. The spectrum of scrotal lesions encountered in our series and their frequencies are summarized in the Table.
Protocol for Scrotal US
Scrotal US is performed with the patient in the supine position and the scrotum supported by a towel placed between the thighs. A large amount of warm gel is used to minimize pressure on the scrotal skin. High-frequency linear-array transducers are recommended for performing the study: 15–8 MHz for neonates and infants and 8–5 MHz for prepubertal and pubertal boys. Because of the superficial position of the organ, we use the fundamental mode and scan each hemi-scrotum in the transverse and longitudinal planes. Study of the spermatic cord is an important part of the examination, particularly in patients with varicocele and suspected testicular torsion. The cord is identified in the inguinal canal, and its course is followed up to the posterosuperior border of the testis.
Testicular size can be determined by measuring the anteroposterior diameter on comparable transverse images of the left and right sides or by calculating testicular volume with the formula for an ellipsoid: V = L x W x H x 0.52, where V = volume, L = length, W = width, and H = height (11). Although these measurements are not acquired routinely, they should be obtained in patients with varicocele, testicular atrophy, or acute scrotum to assess changes in testicular size. Testicular volume is approximately 1–2 cm3 before the age of 12 years and reaches 4 cm3 in pubertal males. In the peripubertal period, a difference of 3 mm in anteroposterior diameter is significant (12).
Color Doppler imaging is performed in all cases to investigate extratesticular vascularization and testicular perfusion, with parameters optimized to display low flow velocities (low wall filter [100 kHz], low pulse repetition frequency [1–2 Hz], and 70%–90% color gain output settings). We add power Doppler imaging in some cases of suspected testicular torsion or tumors to supplement conventional color Doppler imaging. In power Doppler imaging, the color map displays the integrated power of the color signal to depict the presence of blood flow instead of its mean Doppler frequency shift, as in the color Doppler display (13,14). The main theoretical advantages of this method are a higher sensitivity to low blood flow and the fact that the signal is independent of the Doppler angle. The main disadvantage is its susceptibility to movement, which can be a significant drawback in infants. According to some authors (15–17), addition of power Doppler imaging to scrotal imaging increases the sensitivity for detection of blood flow, but this is not the opinion of others (18). In our practice, it has limited usefulness in very small children.
Pulsed-wave Doppler imaging of the intratesticular and epididymal arteries is not performed routinely. However, we include it in cases of epididymo-orchitis and incomplete forms of testicular torsion to increase the diagnostic confidence.
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Normal Scrotal Anatomy at US
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The scrotum is divided by a midline septum (raphe). Each half contains a testis, the epididymis, and the scrotal portion of the spermatic cord.
In neonates and infants, the testis is visualized at US as an ovoid structure of low to medium echogenicity surrounded by an echogenic line, which corresponds to the tunica albuginea (Fig 1a). Testicular echogenicity progressively increases from 8 years of age to puberty with the development of germ cell elements (10). The posterior surface of the tunica albuginea projects into the testis to form the mediastinum, which is seen as a thin echogenic line crossing the testis (Fig 1b). The epididymis is better visualized on longitudinal views and consists of three parts (Fig 1a): (a) The head, which lies on top of the testis, has a pyramidal shape and echogenicity similar to that of the testis. (b) The body, which is the narrow portion, is located behind the testis. (c) The tail is seen as a curved structure at the inferior pole of the testis (2,4).
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Figure 1a. Normal scrotal anatomy and testicular vascularization in a 13-year-old boy. (a) Longitudinal US scan shows the testis (T), which is moderately echogenic and homogeneous. The head of the epididymis (E) lies superior to the testis and has similar echogenicity. The body of the epididymis is located behind the testis, and the tail of the epididymis (t) is located at the inferior pole of the testis. The tunica albuginea (arrows) is seen as a peripheral echogenic line. (b) Longitudinal US scan shows the mediastinum (m) as an echogenic band running across the testis. (c) Color Doppler image shows part of the capsular artery (arrowheads) and the centripetal and centrifugal intratesticular rami.
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Figure 1b. Normal scrotal anatomy and testicular vascularization in a 13-year-old boy. (a) Longitudinal US scan shows the testis (T), which is moderately echogenic and homogeneous. The head of the epididymis (E) lies superior to the testis and has similar echogenicity. The body of the epididymis is located behind the testis, and the tail of the epididymis (t) is located at the inferior pole of the testis. The tunica albuginea (arrows) is seen as a peripheral echogenic line. (b) Longitudinal US scan shows the mediastinum (m) as an echogenic band running across the testis. (c) Color Doppler image shows part of the capsular artery (arrowheads) and the centripetal and centrifugal intratesticular rami.
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Figure 1c. Normal scrotal anatomy and testicular vascularization in a 13-year-old boy. (a) Longitudinal US scan shows the testis (T), which is moderately echogenic and homogeneous. The head of the epididymis (E) lies superior to the testis and has similar echogenicity. The body of the epididymis is located behind the testis, and the tail of the epididymis (t) is located at the inferior pole of the testis. The tunica albuginea (arrows) is seen as a peripheral echogenic line. (b) Longitudinal US scan shows the mediastinum (m) as an echogenic band running across the testis. (c) Color Doppler image shows part of the capsular artery (arrowheads) and the centripetal and centrifugal intratesticular rami.
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There are five testicular appendages, which are the remnants of the mesonephric and paramesonephric ducts (7,19). Three can be identified at US and are particularly apparent in cases of hydrocele: (a) The appendix testis, also known as the hydatid of Morgagni, is usually seen as an oval structure in the groove between the testis and epididymis and is isoechoic to the testis. (b) The appendix epididymis, found at the head of the epididymis, is the same size and echogenicity as the appendix testis but is often pedunculated. (c) The appendix of the epididymal tail is similar to the others but is less commonly identified.
The spermatic cord appears as a smooth linear structure limited by a highly echogenic band on longitudinal scans. On transverse scans, it is ovoid with an echogenic margin. The spermatic cord contains testicular, deferential, and cremasteric arteries and the pampiniform plexus of veins.
Visualization of intratesticular, epididymal, and spermatic cord vessels depends on the Doppler sensitivity of the system, transducer frequency, and expertise of the examiner. In pubertal patients, the capsular artery (branch of the testicular artery) is located beneath the tunica albuginea, and some centripetal and recurrent intratesticular rami are easily identified (Fig 1c). In the small prepubertal testis, the capsular artery is more easily identified than the intratesticular arteries, which are seen as pulsating dots.
The spectral waveform of the intratesticular arteries has a low-flow, low-resistance pattern with a mean resistive index of 0.62 (20,21), although in prepubertal boys diastolic flow may not be detectable (22). The spectral waveform in the epididymis (supplied by deferential and cremasteric arteries) usually has a low-flow, high-resistance pattern.
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Processus Vaginalis–related Disorders
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The processus vaginalis appears at about 13 weeks of fetal development as an outpouching of the parietal peritoneum, through which the testis descends from the abdomen to the scrotum between the 7th and 9th months of fetal life. After testicular descent, the processus vaginalis is obliterated and the scrotal portion of this processus remains as a peritoneum-lined cavity, the tunica vaginalis, surrounding the anterior surface of the testis (23).
Failure of the testis to descend into the scrotum and patency or anomalous closure of the processus vaginalis result in the following conditions: cryptorchidism, inguinoscrotal hernia, and hydrocele.
Cryptorchidism
Failure of the intraabdominal testes to descend into the scrotal sac is known as cryptorchidism. The testes originate within the retroperitoneum and migrate downward through the internal inguinal ring, inguinal canal, and external inguinal ring to the scrotum. The cryptorchid testis may be located at any point along the descent route. The prevalence of this condition is 9.2%–30% in premature infants and 3.4%–5.8% in full-term infants (24). Sonography is useful only for identifying testes in the inguinal canal (the most frequent location [70% of cases]) or the prescrotal region just beyond the external inguinal ring (20%) and should be the initial imaging procedure. The cryptorchid testis is usually smaller and isoechoic or hypoechoic relative to the normally located testis.
When the testis is located in the abdomen, shadowing from bowel gas impairs its visualization at US. Magnetic resonance (MR) imaging, which is highly accurate (94%) for locating testes in the inguinal canal, also may not allow detection of abdominal testes (24,25). Laparoscopic surgery may be required in these cases, since abdominal testes are prone to malignant degeneration (7).
Inguinal-Scrotal Hernia
Inguinal-scrotal hernia is defined as the passage of intestinal loops and/or omentum into the scrotal cavity. The prevalence of inguinal hernia is higher in preterm neonates, especially at 32 weeks gestation (26). The hernia is more frequently located on the right side, since the right processus vaginalis closes later than the left (10).
Physical examination is sufficient to enable diagnosis in most cases. Nevertheless, US examination (which has replaced plain radiography) is indicated in patients with inconclusive physical findings, in patients with acute scrotum, and to investigate contralateral involvement in patients in whom only a unilateral hernia is clinically evident (27).
At gray-scale US, the scrotum is partially occupied by one or more round structures containing air bubbles or fluid (Fig 2). The diagnosis of hernia is achieved by visualization of air bubble movement and/or intestinal peristalsis during the real-time examination. The herniated omentum is seen as a highly echogenic structure. US examination should include both inguinal canals, since a clinically inapparent contralateral hernia can be found in 88% of cases (28). Inguinal rings larger than 4 mm are an indication for prophylactic herniorrhaphy (27,29).
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Figure 2a. Inguinoscrotal hernia in a 5-month-old boy with scrotal swelling. (a) Longitudinal US scan shows a single intestinal loop that has developed a circular configuration to adapt to the scrotum (arrows). The omentum (O) is seen as an echogenic structure. (b) Color Doppler image shows blood flow signal in both the intestinal loop and the omentum. (c) Intraoperative photograph demonstrates the US findings.
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Figure 2b. Inguinoscrotal hernia in a 5-month-old boy with scrotal swelling. (a) Longitudinal US scan shows a single intestinal loop that has developed a circular configuration to adapt to the scrotum (arrows). The omentum (O) is seen as an echogenic structure. (b) Color Doppler image shows blood flow signal in both the intestinal loop and the omentum. (c) Intraoperative photograph demonstrates the US findings.
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Figure 2c. Inguinoscrotal hernia in a 5-month-old boy with scrotal swelling. (a) Longitudinal US scan shows a single intestinal loop that has developed a circular configuration to adapt to the scrotum (arrows). The omentum (O) is seen as an echogenic structure. (b) Color Doppler image shows blood flow signal in both the intestinal loop and the omentum. (c) Intraoperative photograph demonstrates the US findings.
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We routinely use color or power Doppler imaging in inguinal-scrotal hernia to investigate intestinal and testicular perfusion. Urgent surgery is indicated in patients with an akinetic dilated bowel loop (a sign of strangulation) (30) or impaired testicular perfusion, which occurred in one of 40 cases (2.5%) in our series.
Hydrocele
Hydrocele, an abnormal collection of fluid between the visceral and parietal layers of the tunica vaginalis and/or along the spermatic cord, is the most common cause of painless scrotal swelling in children. In the normal scrotum, 1–2 mL of serous fluid may be observed in the potential tunica vaginalis cavity and should not be mistaken for hydrocele. Virtually all hydroceles are congenital in neonates and infants and associated with a patent processus vaginalis, which allows peritoneal fluid to enter the scrotal sac (31). In older children and adolescents, hydroceles are usually acquired and are the result of an inflammatory process, testicular torsion, trauma, or a tumor.
At sonography, congenital hydrocele appears as an anechoic fluid collection surrounding the anterolateral aspects of the testis and sometimes extending to the inguinal canal or as a fluid collection with low-level swirling echoes, which are related to protein aggregation or deposition of cholesterol crystals (Fig 3) (32).
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Figure 3. Hydrocele containing cholesterol crystals. Longitudinal US scan of the right hemiscrotum shows a fluid collection (F) surrounding the testis (T) except where the tunica vaginalis is attached to the scrotal wall (arrows). Weak echoes produced by cholesterol crystals are seen within the fluid.
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Closure of the processus vaginalis above the testis and below the internal inguinal ring leads to a less common type of hydrocele, also known as spermatic cord cyst, which appears as a fluid collection in the spermatic cord (31). Another type, referred to as abdominoscrotal hydrocele, is a highly uncommon entity, with only some 80 reported pediatric cases (33). These are large inguinoscrotal hydroceles that protrude through the internal inguinal ring into the abdominal cavity and manifest clinically as a communicating abdominal-scrotal mass. The exact mechanism by which peritoneal fluid is forced into the abdominal cavity remains speculative (34).
Most congenital hydroceles (80%) resolve spontaneously before the age of 2 years. However, surgical treatment is usually applied in spermatic cord and abdominoscrotal hydroceles.
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Varicocele
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Varicocele involves abnormal dilatation of veins in the pampiniform plexus of the spermatic cord and is relatively common, accounting for 20.5% of cases in our series. Most cases are idiopathic; varicoceles are found mainly in adolescents and young adults and are more frequent on the left side (35).
At sonography, the dilated veins appear as tortuous, anechoic, tubular structures along the spermatic cord. On color and pulsed-wave Doppler images, venous flow is better demonstrated during the Valsalva maneuver (Fig 4). Varicocele may affect testicular growth (36); hence, testicular volumes should be systematically measured and asymmetries assessed with US.
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Figure 4a. Left varicocele in a 15-year-old boy. (a) Longitudinal US scan of the left hemiscrotum shows multiple anechoic structures (arrows) in the supratesticular region and extending behind the upper pole of the testis (T). (b) Color Doppler image shows that the anechoic structures are vascular. (c) Pulsed-wave Doppler image shows a venous waveform with increased flow during the Valsalva maneuver (arrow).
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Figure 4b. Left varicocele in a 15-year-old boy. (a) Longitudinal US scan of the left hemiscrotum shows multiple anechoic structures (arrows) in the supratesticular region and extending behind the upper pole of the testis (T). (b) Color Doppler image shows that the anechoic structures are vascular. (c) Pulsed-wave Doppler image shows a venous waveform with increased flow during the Valsalva maneuver (arrow).
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Figure 4c. Left varicocele in a 15-year-old boy. (a) Longitudinal US scan of the left hemiscrotum shows multiple anechoic structures (arrows) in the supratesticular region and extending behind the upper pole of the testis (T). (b) Color Doppler image shows that the anechoic structures are vascular. (c) Pulsed-wave Doppler image shows a venous waveform with increased flow during the Valsalva maneuver (arrow).
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Treatment of varicoceles is controversial. Surgical treatment is generally reserved for adolescents with testicular growth arrest, cases of high-grade varicocele with abnormal results at semen analysis, adolescents with symptoms (pain, heaviness, swelling), and those with bilateral varicoceles (37).
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Acute Scrotum
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The term acute scrotum refers to a clinical picture of sudden-onset scrotal pain, redness, and swelling, most frequently caused by acute epididymo-orchitis, torsion of the testicular appendages, or testicular torsion. Since scrotal involvement is usually unilateral, we start the examination on the asymptomatic side to have a basis for comparison. Color Doppler imaging, adjusted to visualize low flow velocities, or power Doppler imaging should always be added to the gray-scale study. Pulsed-wave Doppler imaging is not absolutely necessary. Comparable transverse Doppler scans of both testes are essential to study testicular perfusion discrepancies. Patients with absent or clearly decreased blood flow signal should be treated surgically. In cases with inconclusive Doppler perfusion findings, nuclear medicine or MR imaging can assist in the diagnosis and management decisions.
Epididymo-orchitis
Epididymo-orchitis, which is mainly of infectious origin, is a common cause of acute scrotum in children. The infection usually originates in the bladder or prostate gland, spreads through the vas deferens and the lymphatics of the spermatic cord to the epididymis, and finally reaches the testis, causing epididymo-orchitis. Isolated orchitis is very rare. The clinical spectrum ranges from mild tenderness to a severe febrile process. There are two peaks of prevalence: under 2 years of age and over 6 years of age. In our experience, 120 of 156 cases of epididymo-orchitis (77%) occurred in boys over 6 years of age. Imperforate anus, ureteral ectopia to the seminal vesicle, bladder exstrophy, neurogenic bladder, posterior urethral valves, and dysfunctional voiding predispose to epididymitis, particularly in patients under 2 years of age (38) (Fig 5). Some of these predisposing anomalies were observed in 10 of our 156 patients (6.4%).
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Figure 5a. Ectopic vas deferens in a newborn with imperforate anus and left-sided scrotal swelling. (a) Voiding cystourethrogram shows the bladder (B) and a left-sided tubular structure (arrow), which represents an aberrant left vas deferens that terminates within the bladder instead of within the seminal vesicle. (b) Plain radiograph obtained after voiding shows right vesicoureteral reflux (arrowheads) and the left vas deferens (arrow) extending from the bladder to the scrotum.
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Figure 5b. Ectopic vas deferens in a newborn with imperforate anus and left-sided scrotal swelling. (a) Voiding cystourethrogram shows the bladder (B) and a left-sided tubular structure (arrow), which represents an aberrant left vas deferens that terminates within the bladder instead of within the seminal vesicle. (b) Plain radiograph obtained after voiding shows right vesicoureteral reflux (arrowheads) and the left vas deferens (arrow) extending from the bladder to the scrotum.
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The epididymal head is the most affected region, and reactive hydrocele and wall thickening are frequently present. Increased size and, depending on the time of evolution, decreased, increased, or heterogeneous echogenicity of the affected organ are usually observed (Fig 6a). The inflammation produces increased blood flow within the epididymis, testis, or both (Fig 6b). This finding allows the diagnosis to be established in the few cases that show clinical symptoms and normal echogenicity findings (7). Analysis of the epididymal waveform may reveal a low-resistance pattern as compared with the normal pattern (Fig 6b) (39). Occasionally, the entire epididymis is affected (Fig 7).
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Figure 6a. Clinically proved epididymitis in an 11-year-old boy. (a) Longitudinal US scan of the right hemiscrotum shows an enlarged hypoechoic epididymal head (E), reactive hydrocele (h), and thickening of the scrotal wall (*). m = mediastinum. (b) Color and pulsed-wave Doppler image shows increased vascularity in the epididymal head with a low-flow, low-resistance waveform pattern.
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Figure 6b. Clinically proved epididymitis in an 11-year-old boy. (a) Longitudinal US scan of the right hemiscrotum shows an enlarged hypoechoic epididymal head (E), reactive hydrocele (h), and thickening of the scrotal wall (*). m = mediastinum. (b) Color and pulsed-wave Doppler image shows increased vascularity in the epididymal head with a low-flow, low-resistance waveform pattern.
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Figure 7. Acute epididymitis in a 9-year-old boy with scrotal pain and redness. Longitudinal US scan shows that the epididymal head and body (arrows) are enlarged and hypoechoic relative to the normal testis (T). Wall thickening (*) and reactive hydrocele (h) are also seen. Power Doppler imaging showed increased perfusion of the epididymis.
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Malignancies that diffusely infiltrate the testicular parenchyma, such as leukemia and lymphoma, may have a US appearance similar to that of diffuse orchitis. In such cases, the clinical history is extremely important for the differential diagnosis.
Granulomatous epididymo-orchitis is a chronic inflammation occurring in postpubertal boys and consists of a granulomatous reaction to sperm or some microorganisms. The affected part of the epididymis, mainly the tail, is enlarged with heterogeneous echogenicity (Fig 8) (40). At color Doppler imaging, chronic epididymo-orchitis does not demonstrate the increased blood flow typical of acute epididymitis. The sonographic features can be similar to those of epididymal adenomatoid tumor; however, patients with chronic epididymitis present with a painful mass, whereas the tumor is usually painless.
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Figure 8. Granulomatous epididymitis in a 17-year-old boy with a painful scrotal mass. Longitudinal US scan shows a heterogeneous extratesticular mass (cursors) that replaces the epididymal tail. The mass resolved with medical treatment.
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Torsion of the Testicular Appendages
The testicular appendages are remnants of the embryonic mesonephric and paramesonephric ducts and consist of vascularized connective tissue (Fig 9a). The appendages are sessile structures, which predisposes them to torsion, and the appendix testis is most often affected. Torsion of the appendix testis occurs mainly in prepubertal boys (aged 7–14 years), is more frequent on the left side, and is a common cause of acute scrotum in this age group (41).
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Figure 9a. Normal and twisted testicular appendages. (a) Longitudinal power Doppler image of a 10-year-old boy with a hydrocele shows the normal appendix testis as a round structure (arrow) that is isoechoic relative to the testis and is supplied by a branch of the capsular artery. (b) Longitudinal US scan of the left hemiscrotum in a patient with scrotal pain and swelling shows a highly echogenic well-defined mass (arrows) at the upper pole of the epididymis (E). The mass represents a twisted epididymal appendage. T = testis. (c) Color Doppler image of the same patient shows that the twisted appendage is avascular (arrows). Mild reactive hypervascularity is seen at the epididymal head and scrotal tunics.
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Figure 9b. Normal and twisted testicular appendages. (a) Longitudinal power Doppler image of a 10-year-old boy with a hydrocele shows the normal appendix testis as a round structure (arrow) that is isoechoic relative to the testis and is supplied by a branch of the capsular artery. (b) Longitudinal US scan of the left hemiscrotum in a patient with scrotal pain and swelling shows a highly echogenic well-defined mass (arrows) at the upper pole of the epididymis (E). The mass represents a twisted epididymal appendage. T = testis. (c) Color Doppler image of the same patient shows that the twisted appendage is avascular (arrows). Mild reactive hypervascularity is seen at the epididymal head and scrotal tunics.
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Figure 9c. Normal and twisted testicular appendages. (a) Longitudinal power Doppler image of a 10-year-old boy with a hydrocele shows the normal appendix testis as a round structure (arrow) that is isoechoic relative to the testis and is supplied by a branch of the capsular artery. (b) Longitudinal US scan of the left hemiscrotum in a patient with scrotal pain and swelling shows a highly echogenic well-defined mass (arrows) at the upper pole of the epididymis (E). The mass represents a twisted epididymal appendage. T = testis. (c) Color Doppler image of the same patient shows that the twisted appendage is avascular (arrows). Mild reactive hypervascularity is seen at the epididymal head and scrotal tunics.
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Affected patients typically present with gradual or sudden intense pain, usually localized in the upper pole of the testis. In approximately one-third of patients, a nodule of the upper scrotum with bluish skin discoloration ("blue dot" sign) is palpated. This is a pathognomonic feature of this entity, and US examination is not necessarily required for the diagnosis when it is present.
At US, the twisted appendage is seen as a round extratesticular mass with high or mixed echogenicity depending on the evolution time (Fig 9b) (42). Associated findings include an enlarged epididymal head, reactive hydrocele, and scrotal skin thickening. There is no Doppler signal in the twisted appendage, and the epididymis and scrotal tunics are hypervascularized (Fig 9c). Management consists of bed rest and nonsteroidal anti-inflammatory agents. Within days, the twisted appendix may calcify and become detached, leaving a scrotal calcification, known as a scrotolith.
Testicular Torsion
Testicular torsion, or twisting of the spermatic cord, implies first venous and later arterial flow obstruction. The extent of testicular ischemia will depend on the degree of twisting (180°–720°) and the duration of the torsion. Testicular salvage is more likely in patients treated within 4–6 hours after the onset of torsion. On the basis of the surgical findings, two types of testicular torsion are recognized: extravaginal and intravaginal. Extravaginal torsion is seen mainly in newborns and occurs prenatally in most cases (43). The testis is usually necrotic at birth and the hemiscrotum is swollen and discolored. US findings vary, but complex hydrocele and calcification of the tunica albuginea are common (Fig 10). Intravaginal torsion can occur at any age but is more common in adolescents. A predisposing factor is the "bell clapper" deformity, in which the tunica vaginalis joins high on the spermatic cord, leaving the testis free to rotate.
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Figure 10a. Testicular torsion in a newborn with discoloration of the right testicle at birth. (a) Longitudinal US scan shows the testis (T) surrounded by a highly echogenic tunica (arrows), which is probably calcified. A complex hydrocele (h) with several septa occupies the scrotal sac. (b) Intraoperative photograph shows extravaginal torsion of the spermatic cord and the necrotic testis.
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Figure 10b. Testicular torsion in a newborn with discoloration of the right testicle at birth. (a) Longitudinal US scan shows the testis (T) surrounded by a highly echogenic tunica (arrows), which is probably calcified. A complex hydrocele (h) with several septa occupies the scrotal sac. (b) Intraoperative photograph shows extravaginal torsion of the spermatic cord and the necrotic testis.
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Differentiation between testicular torsion and epididymo-orchitis is a clinical challenge, since scrotal pain, swelling, and redness or tenderness are clinical symptoms common to these two entities. The usual teaching is that pain in testicular torsion has a sudden onset, whereas in orchitis it is more gradual. However, about 5% of children with orchitis have sudden onset of pain, and only 50% of patients with testicular torsion have an acute attack (44).
In the early phases of torsion (1–3 hours), testicular echogenicity appears normal. With progression, enlargement of the affected testis and increased or heterogeneous echogenicity are common findings. Sonographic evaluation of the spermatic cord is an essential part of the examination. The point of cord twisting can be identified at the external inguinal orifice (Fig 11). The intrascrotal portion of the edematous cord appears as a round, ovoid, or curled echogenic extratesticular mass, with the epididymal head wrapped around it (Fig 12a). The orientation of the testis, epididymis, and cord may be inverted (three of 50 cases [6%] of torsion in our series) (12).
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Figure 11a. Testicular torsion in a 13-year-old boy. (a) Longitudinal US scan obtained at the level of the external inguinal ring shows an abrupt change in the configuration of the spermatic cord (arrow), a finding suggestive of torsion at this point. (b) Intraoperative photograph shows that the point of cord twisting is at the level of the external inguinal canal (arrow).
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Figure 11b. Testicular torsion in a 13-year-old boy. (a) Longitudinal US scan obtained at the level of the external inguinal ring shows an abrupt change in the configuration of the spermatic cord (arrow), a finding suggestive of torsion at this point. (b) Intraoperative photograph shows that the point of cord twisting is at the level of the external inguinal canal (arrow).
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Figure 12a. Testicular torsion in a 12-year-old boy with right-sided scrotal pain of sudden onset. (a) Longitudinal US scan of the right hemiscrotum shows a round supratesticular mass (M), which represents an edematous spermatic cord. There are several anechoic structures (arrowheads) within the mass, which probably represent obstructed and dilated lymphatic vessels. T = testis. (b) Bilateral transverse color Doppler images show no color flow signals in the right testis, which is enlarged and has heterogeneous echogenicity. Reactive hydrocele (h) and thickening of the scrotal wall (*) are also seen. Testicular torsion and bell clapper deformity were confirmed at surgery.
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Figure 12b. Testicular torsion in a 12-year-old boy with right-sided scrotal pain of sudden onset. (a) Longitudinal US scan of the right hemiscrotum shows a round supratesticular mass (M), which represents an edematous spermatic cord. There are several anechoic structures (arrowheads) within the mass, which probably represent obstructed and dilated lymphatic vessels. T = testis. (b) Bilateral transverse color Doppler images show no color flow signals in the right testis, which is enlarged and has heterogeneous echogenicity. Reactive hydrocele (h) and thickening of the scrotal wall (*) are also seen. Testicular torsion and bell clapper deformity were confirmed at surgery.
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A definitive diagnosis of complete testicular torsion is made when blood flow is visualized on the normal side but is absent on the affected side (Fig 12b). Incomplete torsion refers to cord twisting of less than 360°, in which some arterial flow persists in the affected testis (10 of our 50 cases [20%]). Meticulous comparison of the two testes by using transverse views is mandatory in these cases. Additional information can be obtained from pulsed-wave Doppler imaging, with which decreased or reversed diastolic flow may be evident on the affected side (7), and from scintigraphy and MR imaging (45,46).
Visualization of intratesticular flow in small boys (2–4 years old) has been an extensively reported limitation of color Doppler imaging (7,17,47); this is currently less problematic with the development of more sensitive equipment. Echo enhancers have improved blood flow display in animal models, but they are not used in clinical practice.
As reported, testicular viability can be suggested from gray-scale and color Doppler findings. Normal echogenicity with mild testicular enlargement is a good sign of viability, whereas marked enlargement, heterogeneous echotexture, and scrotal wall hypervascularity are signs of testicular infarction and necrosis (12).
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Scrotal Tumors
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The prevalence of scrotal tumors is estimated at 0.5–2.0 cases per 100,000 boys (48). Scrotal tumors usually manifest as painless scrotal swelling. Owing to its excellent spatial resolution, US is nearly 100% sensitive for identifying scrotal masses (49). The technique allows differentiation between cystic and solid tumors and classification as intra- or extratesticular. The term paratesticular refers to a group of extratesticular lesions that are not easily identified as originating from a particular tissue. Computed tomography (CT) should be reserved for studying spread in malignant tumors, and MR imaging is useful for characterizing the tumor content (eg, fat in teratomas) or better delineating extratesticular solid masses (50). Levels of tumor markers (
-fetoprotein and human chorionic gonadotropin) should be determined for a more precise diagnosis.
Extratesticular Tumors
The most frequent extratesticular tumor is paratesticular rhabdomyosarcoma, which originates in the spermatic cord or scrotal tunics. The majority occur in the first two decades of life and belong to the embryonal histopathologic subtype. At US, paratesticular rhabdomyosarcoma is seen as a hypo- or hyperechoic solid mass that may envelop or invade the epididymis and testis, with hypervascularity at color Doppler imaging (51).
CT is recommended in the initial work-up to determine tumor spread, and MR imaging can be performed to delimit the borders of the mass relative to the epididymis and testis (52). Long-term survival is expected in patients under 10 years of age with disease confined to the scrotum.
Tumors of the epididymis are usually benign. Epididymal cysts, although not true tumors, usually manifest as a palpable mass and are of lymphatic origin. Because they contain clear serous fluid, they are seen as an anechoic, well-defined mass with increased through transmission (Fig 13). Epididymal cysts cannot be differentiated from spermatoceles, which are secondary to obstruction and dilatation of the efferent ductal system. However, the latter occur exclusively in postpubertal boys (49).
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Figure 13. Epididymal cyst in a boy with a palpable scrotal mass. Longitudinal US scan shows a cystic lesion (C) that demonstrates increased sound transmission and replaces almost the entire epididymal head. This US appearance is indistinguishable from that of a spermatocele. T = testis.
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Adenomatoid tumor is rare in children and arises from the poles of the epididymis (1,4,7). At US, this tumor is seen as a smooth, round, well-circumscribed echogenic mass. However, the appearance is not specific and it should be differentiated from granulomatous epididymitis, a chronic form of epididymitis that manifests as a painful palpable mass (Fig 8). At color Doppler imaging, vessels are observed within the adenomatous tumor, whereas usually no vessels are seen in granulomatous epididymitis. Primary malignant tumors of the epididymis are very rare in children; epididymal involvement is mainly due to metastatic spread from B-cell acute lymphoblastic leukemia and B-cell non-Hodgkin lymphoma (49).
Testicular Tumors
Testicular tumors account for 1% of all pediatric solid tumors (53). They have two peaks of prevalence, before 3 years of age and in the postpubertal period, and usually manifest as a painless scrotal mass. Nevertheless, in approximately 10% of patients, testicular tumor is associated with pain due to hemorrhage or infarction, mimicking torsion or epididymitis. Testicular tumors are subdivided into two groups: germ cell tumors and non–germ cell tumors.
Germ Cell Tumors.—
Germ cell tumors result from the transformation of primitive germ cells. These pluripotential cells can remain nondifferentiated (seminomas), become slightly differentiated (embryonal carcinoma), or transform into differentiated embryonal (mature or immature teratomas) or extraembryonal (choriocarcinoma) structures (54).
Yolk sac tumor, also known as endodermal sinus tumor, is the most common germ cell tumor, with most cases occurring before the age of 2 years. Levels of serum markers such as lactate dehydrogenase (the least specific) and -fetoprotein are elevated in more than 90% of patients (55). These markers are also useful in follow-up to check for regression or recurrence of the tumor. The US findings are nonspecific, usually showing a solid mass replacing the entire testis. The presence of hypoechoic areas within the tumor, which indicates areas of necrosis, is a frequent finding in our experience (Fig 14a). As with all germ cell tumors, spread is predominantly via the lymphatic system; hence, the lymphatic pathway should be included in the initial work-up (Fig 14b).
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Figure 14a. Histologically proved yolk sac tumor in a 1-year-old boy with a painless unilateral scrotal mass. (a) Longitudinal US scan of the left hemiscrotum shows a solid tumor (T) replacing the entire testis. The cystic areas (arrowheads) represent tumor necrosis. (b) Contrast-enhanced abdominal CT scan, obtained during the initial work-up, shows retroperitoneal lymphadenopathy (L) with necrotic areas.
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Figure 14b. Histologically proved yolk sac tumor in a 1-year-old boy with a painless unilateral scrotal mass. (a) Longitudinal US scan of the left hemiscrotum shows a solid tumor (T) replacing the entire testis. The cystic areas (arrowheads) represent tumor necrosis. (b) Contrast-enhanced abdominal CT scan, obtained during the initial work-up, shows retroperitoneal lymphadenopathy (L) with necrotic areas.
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The second most common germ cell tumor is teratoma, which is classified as mature or immature. The sonographic appearance depends on the components of the three germinal layers (endodermal, mesodermal, and ectodermal). Teratoma may appear as a cystic lesion with peripheral solid components (Fig 15) or a complex mass with cystic components, calcifications, and echogenic intratumor fat (56). These tumors are usually benign in prepubertal children, so tissue-sparing surgery may be possible; however, in adolescents they are often malignant and require orchidectomy.
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Figure 15. Histologically proved mature teratoma in a 4-year-old boy with a painless scrotal mass. Longitudinal US scan shows a cystic mass (M) with echogenic borders and peripheral solid components (arrows). A rim of normal testis (T) is also seen.
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Testicular epidermoid cyst is the most common benign testicular tumor with no malignant potential. The cyst contains cheesy material and may resemble a solid tumor at US (Fig 16a). Several sonographic patterns have been described: an echogenic lesion surrounded by a hypoechoic or echogenic rim, a target appearance, and an "onion ring" configuration with alternating echogenic and anechoic areas within the lesion (4,5,7). The presence of well-delineated borders and avascularity at color Doppler imaging favors the diagnosis (Fig 16b). In inconclusive cases, MR imaging can aid in identification. On contrast-enhanced images, they are seen as sharply demarcated, low-signal-intensity, nonenhancing lesions (57). Since they have no malignant potential, conservative surgery is recommended in all cases.
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Figure 16a. Surgically proved intratesticular epidermoid cyst. (a) Longitudinal US scan shows a well-circumscribed, solid-appearing intratesticular mass (M) with a hypoechoic halo. T = testis. (b) Color Doppler image shows no blood flow signal within the mass. At conservative surgery, the mass was found to be filled with a cheesy material.
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Figure 16b. Surgically proved intratesticular epidermoid cyst. (a) Longitudinal US scan shows a well-circumscribed, solid-appearing intratesticular mass (M) with a hypoechoic halo. T = testis. (b) Color Doppler image shows no blood flow signal within the mass. At conservative surgery, the mass was found to be filled with a cheesy material.
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Non–Germ Cell Tumors.—
Non–germ cell tumors, which are less frequent than germ cell tumors, can develop from the gonadal stroma (Leydig cell tumor), sex cord cells (Sertoli cell tumor), or sex cord cells plus stroma (gonadoblastoma). Strictly speaking, gonadoblastoma is not actually a tumor but instead is a dysgenetic lesion occurring in the setting of gonadal dysgenesis and intersex syndromes (54).
Leydig cell tumor secretes hormones (androgens or estrogens); hence, one-third of patients present with endocrinopathy (7,55). At US, the tumor is seen as a smoothly demarcated, echo-poor, homogeneous mass (58
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Abstract
LEARNING OBJECTIVES FOR TEST...
