ª Springer Science+Business Media New York 2016
Abdominal Radiology
Abdom Radiol (2016) DOI: 10.1007/s00261-016-0870-0
Review of paratesticular pathology: findings on ultrasound and MRI Refky Nicola ,1 Christine O. Menias,2 Nirvikar Dahiya,2 Kathryn Robinson,3 Amy K. Hara,2 Cary Lynn Siegel3 1
Department of Imaging Science, University Rochester Medical Center, 601 Elmwood Ave PO Box 648, Rochester, NY 14642, USA Department of Radiology, Mayo Clinic-Arizona, 5777 E Mayo Blvd, Scottsdale, AZ 85054, USA 3 Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S Kingshighway BlvD, St Louis, MO 63110, USA 2
Abstract The paratesticular scrotal contents consist of the spermatic cord, epididymis, and fascia, which originate from the embryologic descent of the testis through the abdominal wall. Historically, the primary diagnostic modality has been high-resolution ultrasound. Magnetic resonance imaging (MRI) is an alternative imaging option. Both contrast MRI and diffusion weighted imaging can assist in differentiating between benign and malignant lesions. Unlike the testis which most disease processes are malignant, a wide spectrum of benign disease processes affects the paratesticular region either in isolation or as part of a contiguous disease process from adjacent organs. The familiarity with the epidemiology, pathogenesis, and imaging features can aid the radiologic diagnoses and guide appropriate clinical management. In this article, we review the ultrasound and MR characteristics of various paratesticular pathologies.
The majority of paratesticular disease processes are benign. These include epididymal cysts, scrotal fluid collections (hydrocele, pyocele), inflammatory lesions (acute and chronic epididymitis) or hernias. Paratesticular fluid collections include such as a hydrocele, pyocele, and hematocele. Infection related to acute epididymitis or hernias completes the spectrum of paratesticular pathologies.
Primary solid tumors of the paratesticular region are uncommon and are most often benign, asymptomatic, and slow growing [1]; Table 1 provides a summary of commonly visualized solid paratesticular masses. Metastasis to the paratesticular region are typically from primary tumors of the testes, kidneys, prostate and gastrointestinal tract. The most common primary tumor site is the prostate gland followed by the kidney, stomach, colon, ileum (neuroendocrine or carcinoid) and pancreas. However, the overall prevalence of metastasis is rare, with less than 8% of the epididymal neoplasms representing metastasis [2].
Anatomy The paratesticular structures include the epididymis, spermatic cord, testicular tunics, and vestigial remnants such as the appendices epididymis and testis, a remnant of the paramesonephric duct, appendix of the epididymis, superior and inferior aberrant ductules and paradidymis, a remnant of the mesonephric duct. The spermatic cord consists of the vas deferens, testicular and cremasteric arteries, arteries of the vas deferens, pampiniform venous plexus, lymphatic vessels of the testis, and nerves (Fig. 1). The epididymis is a crescent-shaped structure, which is juxtaposed to the posterolateral aspect of the testis with vas deferens located medially. The paratesticular region includes epithelial, mesothelial, and mesenchymal elements. Each component may result in both malignant and benign tissue transformation.
Imaging evaluation Presented as educational exhibit at RSNA 2013. Correspondence to: Refky Nicola; email: [email protected]
Ultrasound is the primary modality for imaging scrotal masses because of its excellent spatial resolution, low-
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Table 1. Common lesions of the paratesticular region Anatomic location Epididymis
Tunica vaginalis
Spermatic cord Vas deferens Lymphatic channels
Fig. 1. omy.
Lesions Cysts Spermatocele Benign Tumors: Adenomatoid, leiomyoma (Most common) Other benign tumors: fibroma, hemangioma, neurofibroma, and papillary cystadenoma. Malignant: sarcoma (leiomyosarcoma, rhabdyomyosarcoma, and liposarcoma), metastasis, Adenocarcinoma Hematoma Hematocele Pyocele Benign tumor: fibrous pseudotumor (Most common) Malignant tumor: aggressive angiomyxoma Varicocele Benign tumors: Lipoma Malignant tumors: aggressive angiomyxoma Granuloma Benign tumors Lymphangioma Hemangioma
Schematic diagram of the normal intrascrotal anat-
cost, readily availability, and real-time correlation with physical examination. The scrotum as a small parts structure lends well to evaluation by ultrasound providing an excellent balance between penetration and resolution. Ultrasound of the scrotum is performed with the patient in the supine position. A towel is placed between the thighs for support. 7.5 MHz or greater near focused linear array transducer is typically used. Transverse and sagittal views of the scrotum and inguinal regions are obtained. Scrotal skin thickness should also be assessed. Color flow Doppler is also performed and optimized to be sensitive to low velocity flow. Low pulse repetition frequency and low wall filter with appropriate color gain setting (generally over 80%) are the preferred methods.
In the setting of an acute scrotum, the asymptomatic side is evaluated first to ensure the flow parameters are set appropriately. Transverse images of all or a portion of both testes in the field of view are also obtained to allow for side-to-side comparison of the size, echogenicity, and vascularity. On ultrasound, the normal testis is homogeneous echogenic and demonstrates homogenous, echogenicity surrounded by a fibrous band, the tunica albuginea, which is often not visualized in the absence of intrascrotal fluid. Typically, the tunica albuginea is seen as an echogenic line around the testis. The rete testes can be seen as a meshwork of cystic spaces representing prominent tubules. The epididymis is located posterolateral to the testis and is iso- to hyperechoic to the normal testis with equal or diminished vascularity to the testis [3]. MRI is a good problem-solving tool that is selectively used to evaluate the scrotum in patients with ambiguous ultrasound findings. MRI uses non-ionizing radiation and has a superb soft tissue contrast resolution to demonstrate high-quality imaging of the complex anatomy of the testes, and paratesticular space. When necessary, MR is an accurate and cost-effective problemsolving tool particularly for solid masses [4, 5]. MR is also useful for tissue characterization of fat, blood products, fibrous tissue, granulomatous tissue, and tissue perfusion [6, 7]. MR also has a wider field of view and is less operator dependent than US. Also, with the administration of intravenous gadolinium, there is more accurate assessment of the vascularity of testicular lesions than color Doppler US [6]. The pattern of enhancement can also be characterized with the use of gadolinium. The use of gadolinium adds great value in the evaluation of scrotal disorders [7–10]. As a result, MR has a higher accuracy in differentiating paratesticular from intratesticular disease [2].
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Table 2. MRI protocol of paratesticular region Image sequence and plane
FOV (mm)
Section thickness (mm)
GAP (mm)
Matrix size
Applications
Standard anatomic sequences Axial, sagittal, coronal localizer Axial, coronal, sagittal T2 W FSE
400 160
10 4
5 0.5
128 9 256 256 9 192
Axial T1 W SE
340
5
1
256 9 192
Axial T1 W dual-echo spoiled GRE (in-phase and out of phase) Sagittal T2 W fat-suppressed FSE or STIR Axial DW
340
4
1
256 9 192
160
4
0.5
256 9 192
Prescription of subsequent sequences Core sequences for anatomic overview, localizing masses, evaluating the integrity of the tunica albuginea, characterizing masses and fluid collections Characterizing masses and fluid collections, evaluating the integrity of the tunica albuginea, assessing for deep pelvic disease as well as pelvic and inguinal adenopathy Better characterizing blood products due to T2* effects Identifying fluid collections and edema
340
8
2
128 9 128
Axial T2 W fat-suppressed FSE or STIR Axial postcontrast T1 W 3D fat-suppressed spoiled GRE
340 340
6 3
1 0
320 9 256 320 9 256
Axial T2 W fat-suppressed FSE or STIR
160
4
0.5
256 9 192
Axial T1 W dual-echo spoiled GRE (in-phase and out of phase)
340
4
1
256 9 192
Axial DW
340
8
2
128 9 128
Axial pre- and postcontrast T1 W fat-suppressed 3D spoiled GRE Sagittal postcontrast T1 W fat-suppressed 3D spoiled GRE
340
3
0
320 9 256
260
3
0
256 9 192
Fig. 2. A–B 52-year-old male with right greater than left scrotal pain and purulent discharge. A Grayscale Ultrasound image shows diffuse enlargement of the right epididymis consistent with acute epididymitis (white arrow). There is also
Characterizing fluid collections as abscesses Identifying fluid collections and edema Characterizing fluid collections, identifying sites of inflammation, delineating extent of inflammation, assessing for active inflammation in Peyronie disease Evaluating for macroscopic fat content in masses, identifying cystic masses and associated inflammation Better characterizing blood products due to T2* effects, evaluating for intracellular fat in tumors Identifying tumor, assessing response to therapy Evaluating for enhancement of soft-tissue masses, assessing extent of tumor Evaluating for enhancement of soft-tissue masses, assessing extent of tumor
diffuse thickening of the scrotum (blue arrow). B Color Doppler image demonstrates increased vascularity within head of the right epididymis (white arrow).
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Fig. 3. A–C 58-year-old man presents with palpable mass in left hemiscrotum and has a history of acute epididymitis and was managed conservatively. Grayscale and color Doppler
US images show a round hypoechoic paratesticular mass within the left epididymis without internal flow. This is consistent with abscess formation within the epididymis.
MR examination of the scrotum is performed with 1.5 Tesla unit is used at our institution. The patient is positioned supine with feet first with a folded towel placed between the thighs to elevate the scrotum to a horizontal plane. The penis is taped to the abdominal wall in order to remove in from the area of interest. A high-resolution phase array coil is placed over the scrotum with the bottom of the coil over the caudal tip of the scrotum. Axial and coronal T1-and T2 weighted sequences are acquired with a large field of view with 4 mm section thickness. Additionally, axial fat-suppressed T1 images are obtained and high-resolution dual-echo (inphase and out of phase) axial T1 weighted spoiled gradient-echo sequences are implemented to identify fat– water mixtures. These sequences are also used to identify hemorrhage because hemosiderin is better visualized on gradient echo images because of T2* effects. The administration of intravenous gadolinium with fast suppression and single phase of IV contrast at our
institution is routinely performed to characterize conspicuous lesions and to help identify inconspicuous lesions. See Table 2 for MRI protocols.
Inflammation Epididymitis and epididymo-orchitis are common causes of acute scrotal pain in young and middle males [3]. Most cases are due to retrograde infection from the lower urinary tract. The causative organisms are typically Chyamydia and Gonorrheae in patients who are under 35 years old. E.coli and Pseudomonas occur in patients older than 35 years old [11]. 20%–40% of cases of epididymitis are associated with orchitis, which is due to the direct extension of infection into the testicular parenchyma [12]. Acute epididymitis can be either diffuse or focal. On ultrasound, the epididymis is enlarged, and demonstrates decreased echogenicity with increased vascular flow.
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Fig. 4. A–C 69-year-old diabetic male with scrotal swelling and redness. Grayscale and color Doppler US images demonstrate an enlarged inflamed epididymitis with increased vascularity and associated large complex collection with internal septations.
Ultrasound findings also show heterogenous, hypervascular, and enlarged testis which is consistent with orchitis [3]; (Fig. 2A, B). Usually, the acute phase is treated with antibiotics. If there is inadequate treatment, epididymitis and epididymo-orchitis may progress to form an epididymal or testicular abscess or even venous infarction. (Fig. 3A–C). MR is a useful tool to evaluate complicated infections. On MR focal epididymitis can manifest as a heterogeneous area of low signal intensity on T2 weighted images. The epididymis is typically enlarged, and hyperemic on postcontrast T1 weighted images. The presence of increased T2 signal suggests soft tissue edema in the adjacent soft tissues. MR can also assess the severity and extent of infection or inflammation, which is crucial to guide surgical debridement or percutaneous drainage. The infection may break through the tunica vaginalis leading to a formation of a pyocele. Typically, a thick irregular wall with abscesses appears as deep, central T2 hyperintense fluid collections with variable T1 signal and peripheral enhancement. Abscesses restrict diffusion and demonstrate hyperintensity on DWI with corresponding low signal on the ADC map. In cases of known or suspected
abscess, MR is also helpful in identifying and mapping scrotal skin or perineum sinus tracts or fistulous tracts [13]. A fistula manifests as a hypointense linear structure on T1 weighted images with corresponding hyperintensity on fat-suppressed T2 weighted images. Fistula typically demonstrates peripheral enhancement [13].
Pyocele A scrotal abscess or pyocele is typically a complication of epididymo-orchitis. On ultrasound, an abscess appears as a complex heterogeneous fluid collection with or without the presence of gas (Fig. 4). Typically, on MRI, abscesses present hypointense signal on T1 and hyperintense signal on T2-weighted sequences, which is characteristics of fluid contents, with a halo of hyperintense signal on T2 weighted sequences. On contrastenhanced images, only the perilesional parenchyma presents with intense enhancement. MRI is helpful in the characterization of abscess and extent of abscess of formation which is necessary for surgical planning, especially if there is concern for Fournier’s gangrene [11]. If gas is present, it produces bright specular reflectors and dirty posterior acoustic shadowing. These patients
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Fig. 5. 62-year-old diabetic male presents with black scrotum and discharge. A, B Gray scale US images demonstrate diffuse edema and echogenic scrotal inflammation. Note the regions of dirty shadowing corresponding to gas
in the perineum in this patient confirmed to have Fournier’s gangrene. C, D Axial CT images of the pelvis demonstrates extensive air within the scrotum and diffuse scrotal edema.
are usually sicker at presentation and present with acute scrotal pain, a swollen scrotum, elevated white blood cell count, and fever. A scrotal abscess can be further complicated by a necrotizing infection of the perineum which is known as Fournier gangrene, surgical emergency (Fig. 5). Patients frequently will have a history of diabetes, human immunodeficiency virus infection, or other immunosuppressive conditions [14]. Etiologic agents include gas-forming bacteria such as from the Clostridia species or other anaerobes.
over time the hematoma liquefies and becomes anechoic with septations and loculations, demonstrating fluid– fluid levels and low-level echoes [15]. On MR, the early stage of a hematoma is hyperintense on T2 sequence [16]. Over time, the blood products evolve and become hypointense on T2 due to the presence of hemosiderin. If a dual-echo spoiled GRE T1 weighted sequence is included, ‘‘blooming’’ artifact is more pronounced on the in-phase image due to progressive dephasing with the longer echo time. When a scrotal hematoma is present, there maybe also an associated penile or testicular injury [11]. Most often, a hematoma can resolve over time [17]. Rarely, a large hematocele can impede blood flow to the testis because of extrinsic pressure on its vessels, resulting in ischemia or infarction [15]. Therefore, timely evacuation of a hematoma may restore normal blood flow to the testis. Large hematoceles typically are managed surgically, regardless of whether there has been injury to the tunica albuginea or not [15].
Scrotal hematoma Hematomas (hematoceles) within the tunica vaginalis are the most common finding after blunt trauma [15]. Scrotal hematomas are primarily evaluated by ultrasound. However, the sonographic appearance of a hematoma varies with the age of the hematoma, as in the case with all hematomas. Initially, hematomas are echogenic and
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Fig. 6. A–C 30-year old with progressive scrotal swelling feels that there has been a more rapid increase in size recently, previously was a soccer player. Grayscale US images demonstrate a large hydrocele compressing the testis.
Hematocele Hematocele is the accumulation of blood between the visceral and parietal layers of the tunica vaginalis and maybe due to trauma, anticoagulation, testicular torsion, or surgery. Conversely, a hematoma does not necessarily have to limit itself to this anatomy and can exist within the extratesticular structures itself, like the epididymis or may even be intratesticular. MR of hematocele varies depending on their acuity. In the early stage, a hematocele is T2 hyperintense and T1 hyperintense and over time will demonstrate signal characteristics similar to an evolving hematoma. On ultrasound, a hematocele ap-
pears different than a hematoma depending upon phase of observation. Within the early phases, a hematoma is hyperechoic on ultrasound, but with age, they become more aneochic become to resemble a hematocele [18]. With the presence of a scrotal hematoma or hematocele, a thorough search for penile or testicular injury should be done [11]. Most hematoceles resolve with conservative management, but some become fibrotic and calcified [17].
Hydrocele A hydrocele occurs when serous fluid accumulates between the parietal and visceral layers of the tunica
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Fig. 7.
Schematic diagram of a left varicocele.
vaginalis. A small amount of fluid is usually normal on ultrasound and is present in 86% of asymptomatic men [19]. A hydrocele can either be congenital or acquired. If it is congenital, it usually resolves by 18 months of age [14]. An acquired hydrocele is usually reactive to tumor, infection, trauma, or can be idiopathic. The mechanism for an idiopathic hydrocele is unclear, but it is hypothesized that they occur as a result of excessive production of fluid or failure of the mesothelial lining to reabsorb fluid or perhaps absence of efferent lymphatics [14]. On MRI, hydroceles present the typical characteristics of fluid, with homogenously low signal on T1 and hyperintense signal on T2. Septations and calculi may also be identified. Hydroceles are easily diagnosed with ultrasound and are typically anechoic, but can sometimes have low-level echoes or fibrin strands [17, 20]. These low-level echoes have been attributed to protein aggregates secondary to high protein content in the fluid. These particles can be set in motion by ultrasound energy usually in the direction of the beam [21]; (Fig. 6).
Hernias Inguinal hernias are classified as either direct or indirect. An indirect hernia exits the abdominal cavity through the deep internal inguinal ring traversing the inguinal canal to the scrotum. These present more frequently in children with a patent processus vaginalis. Scrotal hernias are most commonly indirect inguinal hernias. A direct hernia is more common in adults and protrudes through Hesselbach triangle. The Hesselbach triangle is formed medially by the lateral border of the rectus muscle, the inferior epigastric artery laterally and inferiorly by the inguinal ligament [22]. The US findings of inguinal hernia are dependent on its contents. Hernias containing bowel are often easier to diagnosis on US than those containing only omentum, since bowel will have a classic ‘‘bowel signature’’ of
concentric walls with alternating echogenic and echopenic structures. Bowel will be fluid filled, demonstrate peristalsis, and show internal echogenicities with dirty shadowing secondary to gas within the lumen. Gas within a hernia may cause shadowing which is a finding also seen in cases of abscess; thus it can be confusing. Inguinal hernias containing only omentum are difficult to diagnose because their appearance overlaps with other echogenic masses, such as lipomas. A Lipoma is a well-defined mass, whereas herniated omentum is more ill-defined, elongated and should be traceable to the inguinal region. Omentum may show movement related to Valsalva whereas a lipoma in the same location may not show significant movement. A hernia with bladder or ureter is common. The ultrasound evaluation of an inguinal hernia is centered on the inferior epigastric vessels which are followed in a transverse plane from within the rectus abdominis down the lower abdomen, toward their origin in the external iliac artery. The inguinal and femoral canals are superficial, non-rigid, and small in caliber. Typically, a 12 MHz linear transducer, light probe pressure and slow controlled movements of the transducer during an examination to maintain anatomical perspective. The normal inguinal canal can become difficult to visualize with excessive compression. It is recommended to use split/dual screen before and after compression with controlled Valsalva maneuvers [23]. MR or CT imaging can also assist in the diagnosis by identifying the presence of bowel loops and the fascial defect medial or lateral to the epigastric vessels at the inguinal ring.
Varicocele Varicoceles are dilated veins of the pampiniform plexus in the spermatic cord and to a lesser extent the smaller cremasteric plexus. The components of the pampiniform plexus are the internal spermatic vein draining the testis, the vein of the vas deferens draining the epididymis, and the cremasteric vein draining the scrotal wall (Fig. 7). The plexus draining into the main testicular vein, which on the left drains into the left renal vein and on the right into the inferior vena cava. Up to 93% of varicoceles occur on the left and 25% are bilateral. The higher occurrence of left-sided varicocele relates to the drainage of the left testicular vein directly into the left renal vein [24]. They can be seen in 15% of asymptomatic men and up to 30%–40% of men with infertility [25]. Men with varicocele present with pain related to passive congestion of the testis. On ultrasound, they are serpiginous tubular anechoic structures within the spermatic cord, representing the dilated pampiniform plexus, and are best seen with color Doppler [26]. On MRI, the signal intensity varies according to blood flow velocity. Slow flowing
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Fig. 8. A–D 48-year old with a 2-year history of a scrotal mass. Gray scale and Color Doppler flow of the testis demonstrate a well-defined echogenic paratesticular mass.
MRI T2 W images in axial, and sagittal plane confirm paratesticular location and homogenous signal pathology confirmed to be an adenomatoid tumor.
varicoceles often have intermediate signal intensity on T1 weighted images and high signal intensity on T2 weighted images. A signal void can also be seen in those with higher velocity flow and also enhance with gadolinium administration.
tumor is smooth, round, and well defined, and can vary in size from 0.4–5 cm [14]. They can exist anywhere along the epididymis but most frequently are found in the tail. They are also seen in the spermatic cord, paratesticular tissues, and tunica albuginea [2, 14]. MR is an excellent tool to confirm their paratesticular origin. Even, if the tumor infiltrates the testis, the tumor is frequently benign and amendable to conservative local resection [27]. On US, adenomatoid tumors present as a well-defined hypoechoic mass within the epididymis [6]. On MR, the tumor is hypointense to the testicular parenchyma and the epididymis on T2 weighted images owing to the fibrous component to the tumor. With the administration of intravenous gadolinium, slow or decreased enhancement relative to the normal testis may be present; which suggests a benign lesion. The added value of MR is the precise localization of the origin of the mass, which enables a confident diagnosis and can guide conservative management [28]; (Fig. 8A–D).
Tumors Benign tumors Adenomatoid Adenomatoid tumor is one of the most common solid epididymal tumor and accounts for approximately a third of all paratesticular neoplasms; only lipomas are more common [2, 14]. Adenomatoid tumors present more commonly between the ages 20 and 50 years. These are benign tumors that arise from mesothelial cells and comprise of cords and tubules of cuboidal to columnar cells with vacuolated cytoplasm and fibrous stroma. Patients usually present with a painless scrotal mass. The
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
A–E 41-year-old male with scrotal mass. Grayscale ultrasound demonstrates a echogenic mass within the right paratesticular region. Axial, coronal T1 W images demonstrate a round hyperintense lesion adjacent to the right testis. T1 W FS with contrast demonstrates homogenously hypointense non-enhancing lesion found to be a spermatic cord lipoma on surgery.
b Fig. 9.
Lipoma Lipoma is a common presenting mass in the paratesticular location, most commonly within the spermatic cord. It accounts for up to 50% all cord tumors. [29] A Lipoma can be variable in size with no specific age predilection. Lipomas are hyperechoic on US, but this appearance is neither sensitive nor specific since hernias, other benign masses and sarcomas can also be echogenic [30, 31]. An atypical lipoma can appear uniformly hypoechoic. Lipomas contain various amounts of fibrous, myxoid, or vascular tissue and greater structural complexity causes an increase in echogenicity. The degree of echogenicity likely reflects the number of interstices within the mass [32]. The diagnosis of a benign lipoma cannot be made
Fig. 10. A–C Axial out of phase, axial FSPGR post-contrast images demonstrate a large hypointense mass with heterogenous enhancement along the course of the sper-
with certainty on US, and most patients undergo surgical resection. MR may serve as a useful adjunct imaging modality. Lipomas have high signal intensity similar to subcutaneous fat on both T1 and T2-weighted imaging, but fat suppression is recommended, since hemorrhagic lesions also have high signal intensity on these pulse sequences. A large lipoma is often difficult to differentiate from a differentiated liposarcoma by imaging alone, and thus surgical excision is necessary for tissue diagnosis (Fig. 9A–E). Sometimes, MRI will demonstrate arterial enhancement within a lipoma which suggests sarcomatous element.
Malignant tumors Malignant tumors are rare in the paratesticular space. The majority of the malignant tumors in this area arise within the epididymis and include sarcoma, metastasis, and adenocarcinoma. Of the sarcoma subtypes, leiomyosarcoma (32%) is the most common, followed by rhabdomyosarcoma (24%), and liposarcoma (20%) [33– 40].
matic cord as it descends in the scrotum. Surgically confirmed to be a well-differentiated liposarcoma.
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
septated, and have a typical hyperintense fat signal on T1 weighted sequences and demonstrate heterogeneous enhancement following contrast administration. Liposarcomas also have thick soft tissue strands or nodules interspersed with fatty elements. The mass also can restrict diffusion. These features help to differentiate liposarcomas from benign lipomas (Figs. 10, 11). Aggressive angiomyxoma An aggressive angiomyxoma is a locally aggressive tumor may involve scrotum, spermatic cord, or perineum without having malignant metastatic potential. While this tumor is almost exclusively seen in females, it can also be seen in males, in the scrotum or spermatic cord [42, 43]. The MR features of perineal aggressive angiomyxomas are isointense or low signal intensity on T1 and high signal intensity on T2 weighted sequences and demonstrate an infiltrating mass [44, 45]. The hyperintense signal on T2 is secondary to the myxomatous content of the tumor [46]. A whorled pattern of signal intensity on T2 weighted images has been reported as a typical characteristic of aggressive angiomyxoma. The contrast enhancement also suggests their inherent vascularity [47, 48]. Fig. 11. A–B 63-year old with acute pain and palpable abnormality of the scrotum. Axial T1FS without and with contrast demonstrate an ovoid mass in the left side of the scrotum with heterogeneous enhancement and complete fat suppression on the axial T1FS without contrast. The mass was reported and pathology showed well-differentiated liposarcoma.
Liposarcoma represents approximately 7% of all paratesticular sarcomas. They are the second most common sarcoma in adults and can present similar to a lipoma; painless scrotal swelling which slowly enlarges. The average age at presentation is 55 years. These sarcomas arise from the mesenchymal cells rather than from malignant degeneration of lipomatous cells [41]. On ultrasound, the findings vary from a hypoechoic mass to a heterogeneous mass with variable echoes, due to internal fat content. On MRI, lipoma will demonstrate hyperintense signal on T1 and hypointense signal on T2 with corresponding loss of signal on fat saturation sequences.
Other paratesticular conditions Cysts The most common epididymal mass is a simple cyst which has been reported in 20–40% of asymptomatic males with 29% having more than one cyst [19]. Epididymal cysts are either spermatoceles or epididymal cysts lined by epithelium containing clear serous fluid. Spermatoceles form from an obstruction and dilatation of the efferent ductal system and are filled with thicker milky fluid containing spermatozoa, lymphocytes, and cellular debris [49]. On Ultrasound and MR imaging clearly depict a cystic, smoothly demarcated lesion typically located in the epididymal head. Spermatoceles may be unilateral, bilateral, solitary, or multiple in location. In most cases, US reliably distinguishes spermatoceles from solid tumors. A spermatocele can, however, be associated with a dilatation of the rete testis and this condition may occasionally mimic a testicular tumor [49, 50]; (Fig. 12A–D). Granuloma
Liposarcoma Liposarcoma constitutes approximately 7% of paratesticular sarcomas. They are second most common sarcoma in adults and can present similar to lipomaspainless scrotal swelling which slowly enlarges. Sonographic findings are variable, ranging from hypoechoic mass to a nonhomogenous mass with variable echoes consistent with fat. Liposarcomas can be quite large,
A post-vasectomy patient may develop a foreign body giant cell reaction to extravasated sperm and present as a granuloma. In an autopsy, sperm granulomas were found in 42% of men who underwent vasectomy and 2.5% of the general population [14]. They can vary in size, but the majority are less than 1 cm [14]. Most sperm granulomas are asymptomatic, some manifest as painful nodules. They are generally well-defined hypoechoic so-
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Fig. 12. A–D 25-year old with large scrotal mass Axial, sagittal, and coronal T2 W and axial T2 W FS shows a large unilocular cyst which was resected due to pain. Pathology confirmed spermatocele.
lid masses on US. Although they can occur anywhere along the ductal system, they most commonly are multiple and found at the cut ends of the vas deferens [49]. Lymphangioma Lymphangioma or, lymphatic malformations, consist of dilated lymphatic channels caused by occlusion of the normal drainage pathways whether congenital or secondary to trauma, surgery, or infection. These masses either represent true tumors that undergo endothelial hyperplasia or simply malformations of the lymphatic vascular pathways [51]. US will demonstrate a multilocular cystic lesion with no internal vascularity. It may be difficult to differentiate from a small hydrocele.
On MR, these masses are multiloculated cystic lesions, which can be quite large and cross fascial planes. They do not communicate with the peritoneal cavity. Like other lymphatic malformations, they contain multiple thin septa with fluid–fluid levels and are T2 hyperintense and T1 hypointense due to their cystic component, and do not restrict diffusion. MR is useful both for the characterization of the mass which can be mistaken for a complex hydrocele on US, and as defining the extent of involvement prior to surgery Fig. 13. Hemangioma Hemangiomas are benign vascular malformations composed of dilated vascular channels with abnormal growth
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Gray scale (A) and color doppler (B) US images demonstrate a multiseptated cystic structure within scrotum. C, D Sagittal and axial T2 weight sequences demonstrate a hyperintense multilocular, multicystic scrotal mass. E Axial T1 FS image demonstrates a multilocular mass without evidence of enhancement. Surgery confirmed a lymphangioma. Note that there is no communication with the peritoneal cavity.
b Fig. 13.
of the endothelial cells. A scrotal hemangioma is extremely rare and consists of 1% of all hemangiomas. They present in infancy and sometimes in later childhood or adolescence. They are typically asymptomatic, although on rare occasions a patient will present with dull, aching pain, heaviness, bleeding and ulceration, which can be misdiagnosed as a varicocele or inguinal hernia [52]. US features include predominantly cystic lesion that may or may not demonstrate vascular flow. It may be difficult to distinguish a hemangioma from a varicocele with ultrasound. US may also be somewhat limiting in defining the degree of the extent of the mass. On MR, hemangiomas are slightly hyperintense relative to muscle on T1 weighted sequences and markedly hyperintense on T2 weighted sequences. A dominant feeding or draining vessel can be seen. Focal areas of signal void are seen and thought to represent fibrous, fatty, or smooth muscle components organized thrombus or fast flowing blood. Phleboliths, if present are small rounded areas of signal void (Fig. 14). MRI imaging may also aid in the diagnosis and can show the extent of local involvement and help identify other vascular masses in patients with syndromes such as Klippel–Trenaunay syndrome. The treatment is usually excision.
Fig. 14. A–B 41-year old with right scrotal mass T2 weight sequence demonstrates a multicystic scrotal mass with multiple fluid levels. T1 W fat-suppressed post-contrast-en-
Fibrous pseudotumor Fibrous pseudotumor results from benign fibrous proliferation of paratesticular tissue which can mimic a neoplasm. The majority of cases arise from the tunica vaginalis with some that arise from the epididymis, spermatic cord, or tunica albuginea. Nearly 50% of patients have an associated hydrocele or hematocele and 30% have a history of trauma or epididymo-orchitis [2]. Most patients present with a painless scrotal mass, but they often have a history of prior infection or trauma [2, 14]. The ultrasound appearance is nonspecific. The tumor may present as a heterogeneous shadowing mass. Calcifications are common. Internal vascularity may be seen on color Doppler. On MR, due to the presence of fibrosis, the lesion has low signal intensity on both T1and T2-weighted images with variable degree of enhancement [3].
Conclusion A wide spectrum of pathologies can affect the paratesticular region. Fortunately, the majority of these lesions are benign in etiology. Many are clinically significant since they may be the source of pain or may result in mass effect upon the testis or rarely mistaken even for an intratesticular mass. High-frequency ultrasound is the mainstay of scrotal imaging in the evaluation of both paratesticular and intratesticular masses due to its short performance time, excellent tissue resolution, low cost, and non-ionizing radiation. In cases, in which ultrasound is inconclusive, MR can serve as a useful problem-solving tool, and has the benefit of a wider field of view, multiplanar capabilities, operator independence, greater tissue characterization of fat, hemorrhage, and tumor.
hanced images demonstrate an enhancing multicystic scrotal mass. Pathology confirmed hemangioma.
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
MR may assist in localizing tumors to the testes or paratesticular region and may guide surgical approach (i.e., excision and frozen section rather orchiectomy) [14]. Acknowledgments. Funding The study was not funded by a Grant.
Compliance with ethical standards Conflicts of interest The authors do not have any conflicts of interest. Ethical approval This article does not contain any studies with human participants or animals performed by any of the authors.
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Abdominal Radiology
Abdom Radiol (2016) DOI: 10.1007/s00261-016-0870-0
Review of paratesticular pathology: findings on ultrasound and MRI Refky Nicola ,1 Christine O. Menias,2 Nirvikar Dahiya,2 Kathryn Robinson,3 Amy K. Hara,2 Cary Lynn Siegel3 1
Department of Imaging Science, University Rochester Medical Center, 601 Elmwood Ave PO Box 648, Rochester, NY 14642, USA Department of Radiology, Mayo Clinic-Arizona, 5777 E Mayo Blvd, Scottsdale, AZ 85054, USA 3 Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S Kingshighway BlvD, St Louis, MO 63110, USA 2
Abstract The paratesticular scrotal contents consist of the spermatic cord, epididymis, and fascia, which originate from the embryologic descent of the testis through the abdominal wall. Historically, the primary diagnostic modality has been high-resolution ultrasound. Magnetic resonance imaging (MRI) is an alternative imaging option. Both contrast MRI and diffusion weighted imaging can assist in differentiating between benign and malignant lesions. Unlike the testis which most disease processes are malignant, a wide spectrum of benign disease processes affects the paratesticular region either in isolation or as part of a contiguous disease process from adjacent organs. The familiarity with the epidemiology, pathogenesis, and imaging features can aid the radiologic diagnoses and guide appropriate clinical management. In this article, we review the ultrasound and MR characteristics of various paratesticular pathologies.
The majority of paratesticular disease processes are benign. These include epididymal cysts, scrotal fluid collections (hydrocele, pyocele), inflammatory lesions (acute and chronic epididymitis) or hernias. Paratesticular fluid collections include such as a hydrocele, pyocele, and hematocele. Infection related to acute epididymitis or hernias completes the spectrum of paratesticular pathologies.
Primary solid tumors of the paratesticular region are uncommon and are most often benign, asymptomatic, and slow growing [1]; Table 1 provides a summary of commonly visualized solid paratesticular masses. Metastasis to the paratesticular region are typically from primary tumors of the testes, kidneys, prostate and gastrointestinal tract. The most common primary tumor site is the prostate gland followed by the kidney, stomach, colon, ileum (neuroendocrine or carcinoid) and pancreas. However, the overall prevalence of metastasis is rare, with less than 8% of the epididymal neoplasms representing metastasis [2].
Anatomy The paratesticular structures include the epididymis, spermatic cord, testicular tunics, and vestigial remnants such as the appendices epididymis and testis, a remnant of the paramesonephric duct, appendix of the epididymis, superior and inferior aberrant ductules and paradidymis, a remnant of the mesonephric duct. The spermatic cord consists of the vas deferens, testicular and cremasteric arteries, arteries of the vas deferens, pampiniform venous plexus, lymphatic vessels of the testis, and nerves (Fig. 1). The epididymis is a crescent-shaped structure, which is juxtaposed to the posterolateral aspect of the testis with vas deferens located medially. The paratesticular region includes epithelial, mesothelial, and mesenchymal elements. Each component may result in both malignant and benign tissue transformation.
Imaging evaluation Presented as educational exhibit at RSNA 2013. Correspondence to: Refky Nicola; email: [email protected]
Ultrasound is the primary modality for imaging scrotal masses because of its excellent spatial resolution, low-
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Table 1. Common lesions of the paratesticular region Anatomic location Epididymis
Tunica vaginalis
Spermatic cord Vas deferens Lymphatic channels
Fig. 1. omy.
Lesions Cysts Spermatocele Benign Tumors: Adenomatoid, leiomyoma (Most common) Other benign tumors: fibroma, hemangioma, neurofibroma, and papillary cystadenoma. Malignant: sarcoma (leiomyosarcoma, rhabdyomyosarcoma, and liposarcoma), metastasis, Adenocarcinoma Hematoma Hematocele Pyocele Benign tumor: fibrous pseudotumor (Most common) Malignant tumor: aggressive angiomyxoma Varicocele Benign tumors: Lipoma Malignant tumors: aggressive angiomyxoma Granuloma Benign tumors Lymphangioma Hemangioma
Schematic diagram of the normal intrascrotal anat-
cost, readily availability, and real-time correlation with physical examination. The scrotum as a small parts structure lends well to evaluation by ultrasound providing an excellent balance between penetration and resolution. Ultrasound of the scrotum is performed with the patient in the supine position. A towel is placed between the thighs for support. 7.5 MHz or greater near focused linear array transducer is typically used. Transverse and sagittal views of the scrotum and inguinal regions are obtained. Scrotal skin thickness should also be assessed. Color flow Doppler is also performed and optimized to be sensitive to low velocity flow. Low pulse repetition frequency and low wall filter with appropriate color gain setting (generally over 80%) are the preferred methods.
In the setting of an acute scrotum, the asymptomatic side is evaluated first to ensure the flow parameters are set appropriately. Transverse images of all or a portion of both testes in the field of view are also obtained to allow for side-to-side comparison of the size, echogenicity, and vascularity. On ultrasound, the normal testis is homogeneous echogenic and demonstrates homogenous, echogenicity surrounded by a fibrous band, the tunica albuginea, which is often not visualized in the absence of intrascrotal fluid. Typically, the tunica albuginea is seen as an echogenic line around the testis. The rete testes can be seen as a meshwork of cystic spaces representing prominent tubules. The epididymis is located posterolateral to the testis and is iso- to hyperechoic to the normal testis with equal or diminished vascularity to the testis [3]. MRI is a good problem-solving tool that is selectively used to evaluate the scrotum in patients with ambiguous ultrasound findings. MRI uses non-ionizing radiation and has a superb soft tissue contrast resolution to demonstrate high-quality imaging of the complex anatomy of the testes, and paratesticular space. When necessary, MR is an accurate and cost-effective problemsolving tool particularly for solid masses [4, 5]. MR is also useful for tissue characterization of fat, blood products, fibrous tissue, granulomatous tissue, and tissue perfusion [6, 7]. MR also has a wider field of view and is less operator dependent than US. Also, with the administration of intravenous gadolinium, there is more accurate assessment of the vascularity of testicular lesions than color Doppler US [6]. The pattern of enhancement can also be characterized with the use of gadolinium. The use of gadolinium adds great value in the evaluation of scrotal disorders [7–10]. As a result, MR has a higher accuracy in differentiating paratesticular from intratesticular disease [2].
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Table 2. MRI protocol of paratesticular region Image sequence and plane
FOV (mm)
Section thickness (mm)
GAP (mm)
Matrix size
Applications
Standard anatomic sequences Axial, sagittal, coronal localizer Axial, coronal, sagittal T2 W FSE
400 160
10 4
5 0.5
128 9 256 256 9 192
Axial T1 W SE
340
5
1
256 9 192
Axial T1 W dual-echo spoiled GRE (in-phase and out of phase) Sagittal T2 W fat-suppressed FSE or STIR Axial DW
340
4
1
256 9 192
160
4
0.5
256 9 192
Prescription of subsequent sequences Core sequences for anatomic overview, localizing masses, evaluating the integrity of the tunica albuginea, characterizing masses and fluid collections Characterizing masses and fluid collections, evaluating the integrity of the tunica albuginea, assessing for deep pelvic disease as well as pelvic and inguinal adenopathy Better characterizing blood products due to T2* effects Identifying fluid collections and edema
340
8
2
128 9 128
Axial T2 W fat-suppressed FSE or STIR Axial postcontrast T1 W 3D fat-suppressed spoiled GRE
340 340
6 3
1 0
320 9 256 320 9 256
Axial T2 W fat-suppressed FSE or STIR
160
4
0.5
256 9 192
Axial T1 W dual-echo spoiled GRE (in-phase and out of phase)
340
4
1
256 9 192
Axial DW
340
8
2
128 9 128
Axial pre- and postcontrast T1 W fat-suppressed 3D spoiled GRE Sagittal postcontrast T1 W fat-suppressed 3D spoiled GRE
340
3
0
320 9 256
260
3
0
256 9 192
Fig. 2. A–B 52-year-old male with right greater than left scrotal pain and purulent discharge. A Grayscale Ultrasound image shows diffuse enlargement of the right epididymis consistent with acute epididymitis (white arrow). There is also
Characterizing fluid collections as abscesses Identifying fluid collections and edema Characterizing fluid collections, identifying sites of inflammation, delineating extent of inflammation, assessing for active inflammation in Peyronie disease Evaluating for macroscopic fat content in masses, identifying cystic masses and associated inflammation Better characterizing blood products due to T2* effects, evaluating for intracellular fat in tumors Identifying tumor, assessing response to therapy Evaluating for enhancement of soft-tissue masses, assessing extent of tumor Evaluating for enhancement of soft-tissue masses, assessing extent of tumor
diffuse thickening of the scrotum (blue arrow). B Color Doppler image demonstrates increased vascularity within head of the right epididymis (white arrow).
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Fig. 3. A–C 58-year-old man presents with palpable mass in left hemiscrotum and has a history of acute epididymitis and was managed conservatively. Grayscale and color Doppler
US images show a round hypoechoic paratesticular mass within the left epididymis without internal flow. This is consistent with abscess formation within the epididymis.
MR examination of the scrotum is performed with 1.5 Tesla unit is used at our institution. The patient is positioned supine with feet first with a folded towel placed between the thighs to elevate the scrotum to a horizontal plane. The penis is taped to the abdominal wall in order to remove in from the area of interest. A high-resolution phase array coil is placed over the scrotum with the bottom of the coil over the caudal tip of the scrotum. Axial and coronal T1-and T2 weighted sequences are acquired with a large field of view with 4 mm section thickness. Additionally, axial fat-suppressed T1 images are obtained and high-resolution dual-echo (inphase and out of phase) axial T1 weighted spoiled gradient-echo sequences are implemented to identify fat– water mixtures. These sequences are also used to identify hemorrhage because hemosiderin is better visualized on gradient echo images because of T2* effects. The administration of intravenous gadolinium with fast suppression and single phase of IV contrast at our
institution is routinely performed to characterize conspicuous lesions and to help identify inconspicuous lesions. See Table 2 for MRI protocols.
Inflammation Epididymitis and epididymo-orchitis are common causes of acute scrotal pain in young and middle males [3]. Most cases are due to retrograde infection from the lower urinary tract. The causative organisms are typically Chyamydia and Gonorrheae in patients who are under 35 years old. E.coli and Pseudomonas occur in patients older than 35 years old [11]. 20%–40% of cases of epididymitis are associated with orchitis, which is due to the direct extension of infection into the testicular parenchyma [12]. Acute epididymitis can be either diffuse or focal. On ultrasound, the epididymis is enlarged, and demonstrates decreased echogenicity with increased vascular flow.
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Fig. 4. A–C 69-year-old diabetic male with scrotal swelling and redness. Grayscale and color Doppler US images demonstrate an enlarged inflamed epididymitis with increased vascularity and associated large complex collection with internal septations.
Ultrasound findings also show heterogenous, hypervascular, and enlarged testis which is consistent with orchitis [3]; (Fig. 2A, B). Usually, the acute phase is treated with antibiotics. If there is inadequate treatment, epididymitis and epididymo-orchitis may progress to form an epididymal or testicular abscess or even venous infarction. (Fig. 3A–C). MR is a useful tool to evaluate complicated infections. On MR focal epididymitis can manifest as a heterogeneous area of low signal intensity on T2 weighted images. The epididymis is typically enlarged, and hyperemic on postcontrast T1 weighted images. The presence of increased T2 signal suggests soft tissue edema in the adjacent soft tissues. MR can also assess the severity and extent of infection or inflammation, which is crucial to guide surgical debridement or percutaneous drainage. The infection may break through the tunica vaginalis leading to a formation of a pyocele. Typically, a thick irregular wall with abscesses appears as deep, central T2 hyperintense fluid collections with variable T1 signal and peripheral enhancement. Abscesses restrict diffusion and demonstrate hyperintensity on DWI with corresponding low signal on the ADC map. In cases of known or suspected
abscess, MR is also helpful in identifying and mapping scrotal skin or perineum sinus tracts or fistulous tracts [13]. A fistula manifests as a hypointense linear structure on T1 weighted images with corresponding hyperintensity on fat-suppressed T2 weighted images. Fistula typically demonstrates peripheral enhancement [13].
Pyocele A scrotal abscess or pyocele is typically a complication of epididymo-orchitis. On ultrasound, an abscess appears as a complex heterogeneous fluid collection with or without the presence of gas (Fig. 4). Typically, on MRI, abscesses present hypointense signal on T1 and hyperintense signal on T2-weighted sequences, which is characteristics of fluid contents, with a halo of hyperintense signal on T2 weighted sequences. On contrastenhanced images, only the perilesional parenchyma presents with intense enhancement. MRI is helpful in the characterization of abscess and extent of abscess of formation which is necessary for surgical planning, especially if there is concern for Fournier’s gangrene [11]. If gas is present, it produces bright specular reflectors and dirty posterior acoustic shadowing. These patients
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Fig. 5. 62-year-old diabetic male presents with black scrotum and discharge. A, B Gray scale US images demonstrate diffuse edema and echogenic scrotal inflammation. Note the regions of dirty shadowing corresponding to gas
in the perineum in this patient confirmed to have Fournier’s gangrene. C, D Axial CT images of the pelvis demonstrates extensive air within the scrotum and diffuse scrotal edema.
are usually sicker at presentation and present with acute scrotal pain, a swollen scrotum, elevated white blood cell count, and fever. A scrotal abscess can be further complicated by a necrotizing infection of the perineum which is known as Fournier gangrene, surgical emergency (Fig. 5). Patients frequently will have a history of diabetes, human immunodeficiency virus infection, or other immunosuppressive conditions [14]. Etiologic agents include gas-forming bacteria such as from the Clostridia species or other anaerobes.
over time the hematoma liquefies and becomes anechoic with septations and loculations, demonstrating fluid– fluid levels and low-level echoes [15]. On MR, the early stage of a hematoma is hyperintense on T2 sequence [16]. Over time, the blood products evolve and become hypointense on T2 due to the presence of hemosiderin. If a dual-echo spoiled GRE T1 weighted sequence is included, ‘‘blooming’’ artifact is more pronounced on the in-phase image due to progressive dephasing with the longer echo time. When a scrotal hematoma is present, there maybe also an associated penile or testicular injury [11]. Most often, a hematoma can resolve over time [17]. Rarely, a large hematocele can impede blood flow to the testis because of extrinsic pressure on its vessels, resulting in ischemia or infarction [15]. Therefore, timely evacuation of a hematoma may restore normal blood flow to the testis. Large hematoceles typically are managed surgically, regardless of whether there has been injury to the tunica albuginea or not [15].
Scrotal hematoma Hematomas (hematoceles) within the tunica vaginalis are the most common finding after blunt trauma [15]. Scrotal hematomas are primarily evaluated by ultrasound. However, the sonographic appearance of a hematoma varies with the age of the hematoma, as in the case with all hematomas. Initially, hematomas are echogenic and
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Fig. 6. A–C 30-year old with progressive scrotal swelling feels that there has been a more rapid increase in size recently, previously was a soccer player. Grayscale US images demonstrate a large hydrocele compressing the testis.
Hematocele Hematocele is the accumulation of blood between the visceral and parietal layers of the tunica vaginalis and maybe due to trauma, anticoagulation, testicular torsion, or surgery. Conversely, a hematoma does not necessarily have to limit itself to this anatomy and can exist within the extratesticular structures itself, like the epididymis or may even be intratesticular. MR of hematocele varies depending on their acuity. In the early stage, a hematocele is T2 hyperintense and T1 hyperintense and over time will demonstrate signal characteristics similar to an evolving hematoma. On ultrasound, a hematocele ap-
pears different than a hematoma depending upon phase of observation. Within the early phases, a hematoma is hyperechoic on ultrasound, but with age, they become more aneochic become to resemble a hematocele [18]. With the presence of a scrotal hematoma or hematocele, a thorough search for penile or testicular injury should be done [11]. Most hematoceles resolve with conservative management, but some become fibrotic and calcified [17].
Hydrocele A hydrocele occurs when serous fluid accumulates between the parietal and visceral layers of the tunica
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Fig. 7.
Schematic diagram of a left varicocele.
vaginalis. A small amount of fluid is usually normal on ultrasound and is present in 86% of asymptomatic men [19]. A hydrocele can either be congenital or acquired. If it is congenital, it usually resolves by 18 months of age [14]. An acquired hydrocele is usually reactive to tumor, infection, trauma, or can be idiopathic. The mechanism for an idiopathic hydrocele is unclear, but it is hypothesized that they occur as a result of excessive production of fluid or failure of the mesothelial lining to reabsorb fluid or perhaps absence of efferent lymphatics [14]. On MRI, hydroceles present the typical characteristics of fluid, with homogenously low signal on T1 and hyperintense signal on T2. Septations and calculi may also be identified. Hydroceles are easily diagnosed with ultrasound and are typically anechoic, but can sometimes have low-level echoes or fibrin strands [17, 20]. These low-level echoes have been attributed to protein aggregates secondary to high protein content in the fluid. These particles can be set in motion by ultrasound energy usually in the direction of the beam [21]; (Fig. 6).
Hernias Inguinal hernias are classified as either direct or indirect. An indirect hernia exits the abdominal cavity through the deep internal inguinal ring traversing the inguinal canal to the scrotum. These present more frequently in children with a patent processus vaginalis. Scrotal hernias are most commonly indirect inguinal hernias. A direct hernia is more common in adults and protrudes through Hesselbach triangle. The Hesselbach triangle is formed medially by the lateral border of the rectus muscle, the inferior epigastric artery laterally and inferiorly by the inguinal ligament [22]. The US findings of inguinal hernia are dependent on its contents. Hernias containing bowel are often easier to diagnosis on US than those containing only omentum, since bowel will have a classic ‘‘bowel signature’’ of
concentric walls with alternating echogenic and echopenic structures. Bowel will be fluid filled, demonstrate peristalsis, and show internal echogenicities with dirty shadowing secondary to gas within the lumen. Gas within a hernia may cause shadowing which is a finding also seen in cases of abscess; thus it can be confusing. Inguinal hernias containing only omentum are difficult to diagnose because their appearance overlaps with other echogenic masses, such as lipomas. A Lipoma is a well-defined mass, whereas herniated omentum is more ill-defined, elongated and should be traceable to the inguinal region. Omentum may show movement related to Valsalva whereas a lipoma in the same location may not show significant movement. A hernia with bladder or ureter is common. The ultrasound evaluation of an inguinal hernia is centered on the inferior epigastric vessels which are followed in a transverse plane from within the rectus abdominis down the lower abdomen, toward their origin in the external iliac artery. The inguinal and femoral canals are superficial, non-rigid, and small in caliber. Typically, a 12 MHz linear transducer, light probe pressure and slow controlled movements of the transducer during an examination to maintain anatomical perspective. The normal inguinal canal can become difficult to visualize with excessive compression. It is recommended to use split/dual screen before and after compression with controlled Valsalva maneuvers [23]. MR or CT imaging can also assist in the diagnosis by identifying the presence of bowel loops and the fascial defect medial or lateral to the epigastric vessels at the inguinal ring.
Varicocele Varicoceles are dilated veins of the pampiniform plexus in the spermatic cord and to a lesser extent the smaller cremasteric plexus. The components of the pampiniform plexus are the internal spermatic vein draining the testis, the vein of the vas deferens draining the epididymis, and the cremasteric vein draining the scrotal wall (Fig. 7). The plexus draining into the main testicular vein, which on the left drains into the left renal vein and on the right into the inferior vena cava. Up to 93% of varicoceles occur on the left and 25% are bilateral. The higher occurrence of left-sided varicocele relates to the drainage of the left testicular vein directly into the left renal vein [24]. They can be seen in 15% of asymptomatic men and up to 30%–40% of men with infertility [25]. Men with varicocele present with pain related to passive congestion of the testis. On ultrasound, they are serpiginous tubular anechoic structures within the spermatic cord, representing the dilated pampiniform plexus, and are best seen with color Doppler [26]. On MRI, the signal intensity varies according to blood flow velocity. Slow flowing
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Fig. 8. A–D 48-year old with a 2-year history of a scrotal mass. Gray scale and Color Doppler flow of the testis demonstrate a well-defined echogenic paratesticular mass.
MRI T2 W images in axial, and sagittal plane confirm paratesticular location and homogenous signal pathology confirmed to be an adenomatoid tumor.
varicoceles often have intermediate signal intensity on T1 weighted images and high signal intensity on T2 weighted images. A signal void can also be seen in those with higher velocity flow and also enhance with gadolinium administration.
tumor is smooth, round, and well defined, and can vary in size from 0.4–5 cm [14]. They can exist anywhere along the epididymis but most frequently are found in the tail. They are also seen in the spermatic cord, paratesticular tissues, and tunica albuginea [2, 14]. MR is an excellent tool to confirm their paratesticular origin. Even, if the tumor infiltrates the testis, the tumor is frequently benign and amendable to conservative local resection [27]. On US, adenomatoid tumors present as a well-defined hypoechoic mass within the epididymis [6]. On MR, the tumor is hypointense to the testicular parenchyma and the epididymis on T2 weighted images owing to the fibrous component to the tumor. With the administration of intravenous gadolinium, slow or decreased enhancement relative to the normal testis may be present; which suggests a benign lesion. The added value of MR is the precise localization of the origin of the mass, which enables a confident diagnosis and can guide conservative management [28]; (Fig. 8A–D).
Tumors Benign tumors Adenomatoid Adenomatoid tumor is one of the most common solid epididymal tumor and accounts for approximately a third of all paratesticular neoplasms; only lipomas are more common [2, 14]. Adenomatoid tumors present more commonly between the ages 20 and 50 years. These are benign tumors that arise from mesothelial cells and comprise of cords and tubules of cuboidal to columnar cells with vacuolated cytoplasm and fibrous stroma. Patients usually present with a painless scrotal mass. The
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
A–E 41-year-old male with scrotal mass. Grayscale ultrasound demonstrates a echogenic mass within the right paratesticular region. Axial, coronal T1 W images demonstrate a round hyperintense lesion adjacent to the right testis. T1 W FS with contrast demonstrates homogenously hypointense non-enhancing lesion found to be a spermatic cord lipoma on surgery.
b Fig. 9.
Lipoma Lipoma is a common presenting mass in the paratesticular location, most commonly within the spermatic cord. It accounts for up to 50% all cord tumors. [29] A Lipoma can be variable in size with no specific age predilection. Lipomas are hyperechoic on US, but this appearance is neither sensitive nor specific since hernias, other benign masses and sarcomas can also be echogenic [30, 31]. An atypical lipoma can appear uniformly hypoechoic. Lipomas contain various amounts of fibrous, myxoid, or vascular tissue and greater structural complexity causes an increase in echogenicity. The degree of echogenicity likely reflects the number of interstices within the mass [32]. The diagnosis of a benign lipoma cannot be made
Fig. 10. A–C Axial out of phase, axial FSPGR post-contrast images demonstrate a large hypointense mass with heterogenous enhancement along the course of the sper-
with certainty on US, and most patients undergo surgical resection. MR may serve as a useful adjunct imaging modality. Lipomas have high signal intensity similar to subcutaneous fat on both T1 and T2-weighted imaging, but fat suppression is recommended, since hemorrhagic lesions also have high signal intensity on these pulse sequences. A large lipoma is often difficult to differentiate from a differentiated liposarcoma by imaging alone, and thus surgical excision is necessary for tissue diagnosis (Fig. 9A–E). Sometimes, MRI will demonstrate arterial enhancement within a lipoma which suggests sarcomatous element.
Malignant tumors Malignant tumors are rare in the paratesticular space. The majority of the malignant tumors in this area arise within the epididymis and include sarcoma, metastasis, and adenocarcinoma. Of the sarcoma subtypes, leiomyosarcoma (32%) is the most common, followed by rhabdomyosarcoma (24%), and liposarcoma (20%) [33– 40].
matic cord as it descends in the scrotum. Surgically confirmed to be a well-differentiated liposarcoma.
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
septated, and have a typical hyperintense fat signal on T1 weighted sequences and demonstrate heterogeneous enhancement following contrast administration. Liposarcomas also have thick soft tissue strands or nodules interspersed with fatty elements. The mass also can restrict diffusion. These features help to differentiate liposarcomas from benign lipomas (Figs. 10, 11). Aggressive angiomyxoma An aggressive angiomyxoma is a locally aggressive tumor may involve scrotum, spermatic cord, or perineum without having malignant metastatic potential. While this tumor is almost exclusively seen in females, it can also be seen in males, in the scrotum or spermatic cord [42, 43]. The MR features of perineal aggressive angiomyxomas are isointense or low signal intensity on T1 and high signal intensity on T2 weighted sequences and demonstrate an infiltrating mass [44, 45]. The hyperintense signal on T2 is secondary to the myxomatous content of the tumor [46]. A whorled pattern of signal intensity on T2 weighted images has been reported as a typical characteristic of aggressive angiomyxoma. The contrast enhancement also suggests their inherent vascularity [47, 48]. Fig. 11. A–B 63-year old with acute pain and palpable abnormality of the scrotum. Axial T1FS without and with contrast demonstrate an ovoid mass in the left side of the scrotum with heterogeneous enhancement and complete fat suppression on the axial T1FS without contrast. The mass was reported and pathology showed well-differentiated liposarcoma.
Liposarcoma represents approximately 7% of all paratesticular sarcomas. They are the second most common sarcoma in adults and can present similar to a lipoma; painless scrotal swelling which slowly enlarges. The average age at presentation is 55 years. These sarcomas arise from the mesenchymal cells rather than from malignant degeneration of lipomatous cells [41]. On ultrasound, the findings vary from a hypoechoic mass to a heterogeneous mass with variable echoes, due to internal fat content. On MRI, lipoma will demonstrate hyperintense signal on T1 and hypointense signal on T2 with corresponding loss of signal on fat saturation sequences.
Other paratesticular conditions Cysts The most common epididymal mass is a simple cyst which has been reported in 20–40% of asymptomatic males with 29% having more than one cyst [19]. Epididymal cysts are either spermatoceles or epididymal cysts lined by epithelium containing clear serous fluid. Spermatoceles form from an obstruction and dilatation of the efferent ductal system and are filled with thicker milky fluid containing spermatozoa, lymphocytes, and cellular debris [49]. On Ultrasound and MR imaging clearly depict a cystic, smoothly demarcated lesion typically located in the epididymal head. Spermatoceles may be unilateral, bilateral, solitary, or multiple in location. In most cases, US reliably distinguishes spermatoceles from solid tumors. A spermatocele can, however, be associated with a dilatation of the rete testis and this condition may occasionally mimic a testicular tumor [49, 50]; (Fig. 12A–D). Granuloma
Liposarcoma Liposarcoma constitutes approximately 7% of paratesticular sarcomas. They are second most common sarcoma in adults and can present similar to lipomaspainless scrotal swelling which slowly enlarges. Sonographic findings are variable, ranging from hypoechoic mass to a nonhomogenous mass with variable echoes consistent with fat. Liposarcomas can be quite large,
A post-vasectomy patient may develop a foreign body giant cell reaction to extravasated sperm and present as a granuloma. In an autopsy, sperm granulomas were found in 42% of men who underwent vasectomy and 2.5% of the general population [14]. They can vary in size, but the majority are less than 1 cm [14]. Most sperm granulomas are asymptomatic, some manifest as painful nodules. They are generally well-defined hypoechoic so-
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Fig. 12. A–D 25-year old with large scrotal mass Axial, sagittal, and coronal T2 W and axial T2 W FS shows a large unilocular cyst which was resected due to pain. Pathology confirmed spermatocele.
lid masses on US. Although they can occur anywhere along the ductal system, they most commonly are multiple and found at the cut ends of the vas deferens [49]. Lymphangioma Lymphangioma or, lymphatic malformations, consist of dilated lymphatic channels caused by occlusion of the normal drainage pathways whether congenital or secondary to trauma, surgery, or infection. These masses either represent true tumors that undergo endothelial hyperplasia or simply malformations of the lymphatic vascular pathways [51]. US will demonstrate a multilocular cystic lesion with no internal vascularity. It may be difficult to differentiate from a small hydrocele.
On MR, these masses are multiloculated cystic lesions, which can be quite large and cross fascial planes. They do not communicate with the peritoneal cavity. Like other lymphatic malformations, they contain multiple thin septa with fluid–fluid levels and are T2 hyperintense and T1 hypointense due to their cystic component, and do not restrict diffusion. MR is useful both for the characterization of the mass which can be mistaken for a complex hydrocele on US, and as defining the extent of involvement prior to surgery Fig. 13. Hemangioma Hemangiomas are benign vascular malformations composed of dilated vascular channels with abnormal growth
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
Gray scale (A) and color doppler (B) US images demonstrate a multiseptated cystic structure within scrotum. C, D Sagittal and axial T2 weight sequences demonstrate a hyperintense multilocular, multicystic scrotal mass. E Axial T1 FS image demonstrates a multilocular mass without evidence of enhancement. Surgery confirmed a lymphangioma. Note that there is no communication with the peritoneal cavity.
b Fig. 13.
of the endothelial cells. A scrotal hemangioma is extremely rare and consists of 1% of all hemangiomas. They present in infancy and sometimes in later childhood or adolescence. They are typically asymptomatic, although on rare occasions a patient will present with dull, aching pain, heaviness, bleeding and ulceration, which can be misdiagnosed as a varicocele or inguinal hernia [52]. US features include predominantly cystic lesion that may or may not demonstrate vascular flow. It may be difficult to distinguish a hemangioma from a varicocele with ultrasound. US may also be somewhat limiting in defining the degree of the extent of the mass. On MR, hemangiomas are slightly hyperintense relative to muscle on T1 weighted sequences and markedly hyperintense on T2 weighted sequences. A dominant feeding or draining vessel can be seen. Focal areas of signal void are seen and thought to represent fibrous, fatty, or smooth muscle components organized thrombus or fast flowing blood. Phleboliths, if present are small rounded areas of signal void (Fig. 14). MRI imaging may also aid in the diagnosis and can show the extent of local involvement and help identify other vascular masses in patients with syndromes such as Klippel–Trenaunay syndrome. The treatment is usually excision.
Fig. 14. A–B 41-year old with right scrotal mass T2 weight sequence demonstrates a multicystic scrotal mass with multiple fluid levels. T1 W fat-suppressed post-contrast-en-
Fibrous pseudotumor Fibrous pseudotumor results from benign fibrous proliferation of paratesticular tissue which can mimic a neoplasm. The majority of cases arise from the tunica vaginalis with some that arise from the epididymis, spermatic cord, or tunica albuginea. Nearly 50% of patients have an associated hydrocele or hematocele and 30% have a history of trauma or epididymo-orchitis [2]. Most patients present with a painless scrotal mass, but they often have a history of prior infection or trauma [2, 14]. The ultrasound appearance is nonspecific. The tumor may present as a heterogeneous shadowing mass. Calcifications are common. Internal vascularity may be seen on color Doppler. On MR, due to the presence of fibrosis, the lesion has low signal intensity on both T1and T2-weighted images with variable degree of enhancement [3].
Conclusion A wide spectrum of pathologies can affect the paratesticular region. Fortunately, the majority of these lesions are benign in etiology. Many are clinically significant since they may be the source of pain or may result in mass effect upon the testis or rarely mistaken even for an intratesticular mass. High-frequency ultrasound is the mainstay of scrotal imaging in the evaluation of both paratesticular and intratesticular masses due to its short performance time, excellent tissue resolution, low cost, and non-ionizing radiation. In cases, in which ultrasound is inconclusive, MR can serve as a useful problem-solving tool, and has the benefit of a wider field of view, multiplanar capabilities, operator independence, greater tissue characterization of fat, hemorrhage, and tumor.
hanced images demonstrate an enhancing multicystic scrotal mass. Pathology confirmed hemangioma.
R. Nicola et al.: Review of paratesticular pathology: findings on ultrasound and MRI
MR may assist in localizing tumors to the testes or paratesticular region and may guide surgical approach (i.e., excision and frozen section rather orchiectomy) [14]. Acknowledgments. Funding The study was not funded by a Grant.
Compliance with ethical standards Conflicts of interest The authors do not have any conflicts of interest. Ethical approval This article does not contain any studies with human participants or animals performed by any of the authors.
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