US of the Tunica Vaginalis Testis: Anatomic Relationships

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EDUCATION EXHIBIT
2017
US of the Tunica Vaginalis Testis: Anatomic
Relationships and
Pathologic Conditions1
Online-Only
CME
See www.rsna
.org/education
/rg_cme.html
LEARNING
OBJECTIVES
After reading this
article and taking
the test, the reader
will be able to:
■■Describe
the embryologic development and anatomy
of the tunica vaginalis.
■■Identify
the US
findings of congenital, infectious,
inflammatory, traumatic, and neoplastic disorders of the
tunica vaginalis.
■■Discuss
the
clinical and surgical
management of lesions of the tunica
vaginalis.
TEACHING
POINTS
See last page
Victoria Garriga, MD • Angel Serrano, MD • Anna Marin, MD
Santiago Medrano, MD • Nuria Roson, MD • Xavier Pruna, PhD
Extratesticular lesions are common incidental findings at ultrasonography (US) among men and boys. Most lesions originate from or depend on the tunica vaginalis, a mesothelium-lined sac with a visceral
layer and a parietal layer. The tunica vaginalis is formed when the superior portion of the processus vaginalis closes during embryologic development. Abnormal closure of the processus vaginalis leads to congenital anomalies of the tunica vaginalis, such as complete or partial
patency of the processus vaginalis, spermatic cord hydrocele, and inguinoscrotal hernia. The proximity of the visceral layer to the testis explains the reactive involvement seen in epididymo-orchitis, with resultant pyocele or abscess formation. The tunica vaginalis also may be affected by inflammatory and traumatic disorders such as scrotal calculi,
fibrous pseudotumor, or hematocele. These lesions manifest as solid or
heterogeneous tumorlike masses. Lesions of mesothelial origin, such
as adenomatoid tumor, tunica cyst, and mesothelioma, may involve
the tunica vaginalis. Entrapped mesenchymal cells can lead to lipoma,
leiomyoma, or sarcoma, although these tumors are uncommon in the
tunica vaginalis. US is not useful for differentiating between benign
and malignant tumors; however, some characteristic findings may help
in planning the best surgical approach. Knowledge of the embryologic
development, anatomic relationships, and pathologic disorders of the
tunica vaginalis is essential to narrow the differential diagnosis of an
extratesticular lesion. In most cases, US findings in combination with
clinical assessment can indicate whether nonsurgical management or
testis-sparing surgery is warranted.
©
RSNA, 2009 • radiographics.rsna.org
Abbreviation: H-E = hematoxylin-eosin
RadioGraphics 2009; 29:2017–2032 • Published online 10.1148/rg.297095040 • Content Codes:
1
From the Departments of Radiology (V.G., A.M., S.M., N.R., X.P.) and Pathology (A.S.), Hospital General de Granollers, Fundació Hospital-Asil
de Granollers, Avd Francesc Ribas, s/n, 08400 Granollers, Spain. Presented as an education exhibit at the 2008 RSNA Annual Meeting. Received
March 3, 2009; revision requested April 8 and received May 14; accepted May 18. All authors have no financial relationships to disclose. Address
correspondence to V.G. (e-mail: 28457vgf@comb.cat).
©
RSNA, 2009
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Introduction
The widespread use of scrotal ultrasonography
(US) has led to increased detection of scrotal lesions, most of which are extratesticular in origin.
An extratesticular lesion may originate from the
epididymis, spermatic cord, or tunica vaginalis.
Knowledge of the embryologic development and
anatomy of the tunica vaginalis is essential to accurately characterize the lesion.
The tunica vaginalis is a mesothelium-lined
sac that results from closure of the superior portion of the processus vaginalis. This fascial strucTeaching ture normally covers the entire testis except the
Point
posterior border. It has a visceral layer and an
outer parietal layer that lines the internal spermatic fascia of the scrotal wall. These layers and
the potential sac they delimit may be affected by
a wide variety of pathologic processes, including
congenital, infectious, inflammatory, traumatic,
and neoplastic disorders. In some cases, the clinical significance of these disorders poses a therapeutic dilemma; urologists must decide whether
to perform orchiectomy, use a more conservative
testis-sparing inguinal approach, or opt for medical management with watchful waiting (1). In
this article, we review the embryologic development and anatomy of the tunica vaginalis and the
characteristic US features of the most common
disorders affecting the tunica vaginalis so as to
facilitate recognition of these disorders and, thus,
allow their appropriate management.
Embryologic Development
and Anatomic Relationships
In the 2nd and 3rd months of gestation, the
processus vaginalis, a socklike evagination of the
peritoneum, elongates caudally through the abdominal wall and into the scrotal folds. The processus vaginalis forms just anterior to the developing testes and a ligamentous cord that extends,
along with the gubernaculum, from the testes to
the labioscrotal fold (Fig 1) (2,3).
As the processus vaginalis begins to evaginate, it becomes ensheathed by fascial extensions
of the abdominal wall. The fascia transversalis
becomes the internal spermatic fascia, the innermost layer of the sheath; the internal oblique
muscle forms the cremaster muscle, the intermediate layer; and the external oblique muscle gives
rise to the external spermatic fascia, the outermost layer. (The transversus abdominis muscle
is discontinuous inferiorly and does not contrib-
Figure 1. Diagram shows the normal embryologic
development of the processus vaginalis, which arises
as an outpouching of the parietal peritoneum at the
beginning of the 3rd month of gestation. After the
testis descends into the scrotum (between the 7th and
9th months of gestation), the processus vaginalis is
obliterated.
Figure 2. Diagram shows the abdominal fascial
extensions that constitute the scrotal wall. The fascia
transversalis (fT) becomes the internal spermatic fascia
(ISf), the internal oblique muscle (IOm) forms the
cremasteric muscle (Cm), and the external oblique
muscle (EOm) gives rise to the external spermatic fascia (ESf). The transversus abdominis muscle (TAm)
does not contribute to the scrotal wall.
ute to the scrotal wall.) These fascial layers are
invested within a fibromuscular sac that contains
the dartos muscle, which is embedded in loose
areolar tissue (Fig 2) (2).
Between the 7th and 9th months of gestation,
the testes descend from the abdomen to the scrotum through the processus vaginalis (3). Shortly
afterward, in response to the same hormonal
stimuli that cause the testes to descend, the gubernaculum testis regresses, and the processus
vaginalis is obliterated (4). Three steps occur in
the normal obliteration of the processus vaginalis:
(a) closure of the deep inguinal ring, (b) closure
of the area just above the testis, and (c) atresia of
the processus vaginalis between the two constrictions (the funicular process) (5). These steps lead
to formation of the potential cavity of the tunica
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Figure 3. Patent processus vaginalis in an asymptomatic 8-month-old boy. Longitudinal US image
shows a tubular structure from the deep inguinal ring
to the scrotum. The tube is delimited by an iso- to
hyperechoic wall (arrowheads), a finding indicative of
the collapsed lumen of the processus vaginalis.
Figure 4. Partially patent processus vaginalis and cryptorchism. (a) Diagram shows an undescended testis in the upper scrotum and a distal hydrocele. (b) Longitudinal US image in a
9-month-old boy shows a cryptorchid testis (T) within a septate (arrow) processus vaginalis.
vaginalis, a mesothelium-lined sac composed of a
visceral layer and a parietal layer. The visceral layer
envelops all but the posterior aspect of the testis,
and the parietal layer lies against the scrotal wall.
These vaginal layers contain nonstriated smooth
muscle cells that transport spermatozoa toward
the rete testis and into the epididymis. The visceral
layer is closely adherent to the tunica albuginea, a
fibrous capsule that covers the testis and extends
into the gland, dividing it into lobules (3,6).
Congenital Abnormalities
Teaching
Point
Incomplete closure of the processus vaginalis
leads to a variety of abnormalities. Complete
patency of the processus vaginalis may result
in a communicating hydrocele or a congenital
inguinoscrotal hernia. Incomplete atresia of the
funicular process may result in a funicular or encysted hydrocele of the cord (5).
Patent Processus Vaginalis
The processus vaginalis remains patent at birth
in 20% of the population. Most boys born with a
patent processus vaginalis remain asymptomatic
throughout life. A persistent processus vaginalis
often closes during the 1st year of life, probably in
response to the surge in serum testosterone that
normally occurs at 1–2 months of age. Conditions that may be associated with delayed closure
or nonclosure of the processus vaginalis include
premature birth, cystic fibrosis, Ehlers-Danlos
syndrome, hip dysplasia, peritoneal dialysis, or
ventriculoperitoneal shunt (7). Patency of the
processus vaginalis may result in failure of the testis to descend into the scrotum, communicating
hydrocele, or indirect inguinoscrotal hernia. In the
absence of these associated anomalies, complete
patency of the processus vaginalis may go unrecognized. At US, the two collapsed layers of the
tunica vaginalis may be identifiable as isoechoic to
hyperechoic linear bands extending from the internal inguinal ring to the scrotum (Fig 3). A partially
patent processus vaginalis may be associated with
a distal partially undescended testis, also called a
gliding testis (8). In these cases, the testis is seen
below the deep inguinal ring and is impeded from
reaching the end of the scrotal pouch by one or
more septa within the processus vaginalis. A distal
scrotal hydrocele also may be present (Fig 4). Surgical orchiopexy is recommended to avoid subsequent testicular damage.
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Figure 5. Funicular hydrocele. (a) Diagram shows a fluid collection along the spermatic
cord and in the peritoneum, mimicking a peritoneal diverticulum. The internal adhesions
are remnants of partial constrictions. (b) Longitudinal US image in a 2-year-old boy with a
suspected inguinal hernia shows a fluid collection communicating with the peritoneum and
fibrous constrictions (arrows) that produce a beaded appearance of the cord.
Figure 6. Encysted hydrocele. (a) Diagram shows a fluid collection that does not communicate with the peritoneum or the scrotum. (b) Longitudinal US image in a 12-year-old
boy shows a complex ovoid encysted lesion proximal to the testis (T), a finding indicative of
an encysted hydrocele with protein and cholesterol contents.
Spermatic Cord Hydrocele
Hydrocele of the spermatic cord is a rare anomaly that results from an aberration in the closure
of the processus vaginalis. It is a loculated fluid
collection along the spermatic cord, separate
from the testis and the epididymis and located
above them. Clinically it manifests as groin swelling that is indistinguishable from a mass at palpation. There are three types of spermatic cord hydrocele: communicating, funicular, and encysted.
A communicating hydrocele is associated with
complete patency of the processus vaginalis. At
US, it appears as a fluid collection that extends
from the pelvis through the deep inguinal ring to
the scrotum.
A funicular hydrocele is a result of abnormal
obliteration of the deep inguinal ring, with constriction just above the testis. At US, it resembles
a peritoneal diverticulum, appearing as a fluid
collection that communicates with the peritoneum at the deep inguinal ring and that does not
surround the testicle (7). A funicular hydrocele
may contain fibrous adhesions, the remnants of
partial constrictions and inflammatory changes
(5). The resultant beaded appearance of the spermatic cord and thickened tunica vaginalis gave
rise to the term pachyvaginalitis (Fig 5). Funicular hydroceles become larger with increased intraperitoneal pressure during straining and smaller
during relaxation. They are prevalent in children
and premature infants; however, they may be
incidentally discovered in adults. They are con-
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Figure 7. Inguinoscrotal hernia. (a) Diagram shows the passage of intestinal loops into
the scrotal cavity. (b) Longitudinal US image of the spermatic cord in a 1-year-old boy
shows an inguinoscrotal hernia that contains bowel (arrowheads). A patent internal inguinal
ring also is seen (arrows).
Inguinoscrotal Hernia
Figure 8. Inguinoscrotal hernia in a 10-month-old
boy with a right groin mass. Longitudinal color Doppler US image shows hyperechoic gas bubbles and
fluid within the bowel lumen. The testis (T), seen distally, is surrounded by a small hydrocele. Bowel wall
vascularity and peristaltic movement also are visible.
sidered a type of potential indirect hernia, and
herniotomy usually is performed.
An encysted hydrocele is enclosed between
two constrictions at the deep inguinal ring, just
above the testis. It does not communicate with
the peritoneum. An encysted hydrocele may be
located anywhere along the spermatic cord. It
may be any size or shape, but it does not change
with increased peritoneal pressure. At US, an
ovoid or round mass is seen in the groin along
the spermatic cord; internal echogenicity varies
depending on the contents. The presence of cholesterol deposits may explain an isoechoic appearance of the mass (Fig 6).
An inguinoscrotal hernia occurs when an intestinal loop or part of the omentum passes into the
scrotal cavity through an incompletely obliterated
processus vaginalis. Inguinoscrotal hernias are
most common in preterm neonates, but they also
may develop in adults. The diagnosis usually is
established at physical examination. US may be
indicated to differentiate an inguinoscrotal hernia
from other conditions and to investigate contralateral involvement (3). At US, intestinal loops within
the scrotum appear as tubular structures containing hyperechoic air bubbles or fluid. Peristalsis of
bowel loops is easily detected because of the movement of gas bubbles (Fig 7). The herniated omentum appears as a highly echogenic structure. Color
Doppler US may be used to demonstrate vascularity within the omentum, as well as peristaltic
movement in the bowel loops (Fig 8). Hernias
that contain omentum may be more difficult to
diagnose because their appearance is similar to
that of lipomas. However, whereas a lipoma appears as a well-defined or encapsulated mass,
herniated omentum is more elongated, and
branching omental vessels are easily identified at
color Doppler US.
Infectious Disorders
Pyocele and Scrotal Abscess
A pyocele may occur as a complication of trauma,
surgery, or epididymo-orchitis when the mesothelial lining of the tunica vaginalis is breached and
infection ensues. Clinical history and physical
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examination of a painful scrotum help in making
the diagnosis. At US, a pyocele often appears as
a septate or complex heterogeneous fluid collection (Fig 9). A pyocele organized as an abscess
has a well-defined hyperemic wall. Gas bubbles
within the fluid collection appear as hyperechoic
foci with “dirty shadowing” (Fig 10). In most
cases, conservative treatment with antibiotics is
sufficient. However, a scrotal abscess complicated
by necrotizing infection of the perineum requires
surgical débridement (3).
Scrotal Tuberculosis
Teaching
Point
Tuberculosis is the most common opportunistic
infection in patients with human immunodeficiency viral infection. Extension from the lower
urinary tract and hematogenous dissemination
are postulated pathways of epididymal infection.
From the epididymis, infection easily spreads to
the visceral layer of the tunica vaginalis, which
lines the epididymis. Secondary involvement of
the ipsilateral testis may occur if the patient does
not receive appropriate treatment, but it is uncommon (9). The marked heterogeneity of imaging features of tuberculosis may be explained by
the variety of pathologic components. In the initial stage, desquamated cells, inflammatory cells,
and bacilli fill the epididymis. Posterior necrosis
of tubules, caseation, and extension of infection
into interstitial tissues produce an exudative,
granulomatous, fibrous reaction in the tunica
vaginalis and testis (10).
At initial US examinations, the epididymis
has a nonspecific nodular or diffusely enlarged
heterogeneous appearance, a finding indicative of
granulomas due to an inflammatory reaction with
infiltration by Langerhans cells. The testis is not
usually involved, except by direct extension from
a tuberculous abscess. In advanced scrotal tuberculosis, US depicts epididymo-orchitic or vaginal
nodules without flow, findings indicative of tuberculomas with cystic necrosis. These nodules
may be the only US finding of tunica vaginalis
involvement, and the testis and epididymis may
remain intact (Fig 11). Hydrocele, sinus tract,
and calcifications also may be seen (10). Antituberculous chemotherapy is the initial treatment
for tuberculosis. Rifampicin injection into the tunica vaginalis has been proposed as an alternative
treatment (11). Because testicular tumorlike lesions are impossible to differentiate from testicular tumors, early surgical exploration is necessary
if the lesion does not respond to antituberculous
chemotherapy.
Figure 9. Pyocele. Longitudinal color Doppler US
image in a 24-year-old man with scrotal pain shows a
septate fluid collection (arrows) surrounding a hyperemic, inflamed testis.
Figure 10. Scrotal abscess. Axial color Doppler US
image in a 30-year-old man with a painful scrotal mass
shows a complex, heterogeneous fluid collection with
an echogenic and hyperemic wall, findings indicative
of an abscess (black arrowheads). Reactive thickening
and hyperemia of the parietal vaginal layer (white arrowheads) also are seen.
Scrotal Schistosomiasis
Schistosomiasis comprises a group of infections
caused by parasitic trematodes of the genus Schistosoma. Trematodes are endemic to tropical countries, but schistosomiasis is becoming increasingly common in developed countries because of
immigration and tourism. Of the 10 species that
can infect humans, Schistosoma haematobium is
responsible for the vast majority of male genital
infections. It primarily affects the genitourinary
tract, including the prostate, seminal vesicles, and
scrotum. At US, testicular and epididymal lesions
may simulate malignancy, infarction, or nonspecific signs of epididymo-orchitis. Tunica vaginalis
involvement results in septate collections, multi-
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Figure 11. Scrotal tuberculosis. (a) Axial US image in a 38-year-old man with a 5-month history of
scrotal pain and swelling shows a well-demarcated hypoechoic lesion involving the tunica vaginalis (arrow)
and multiple ill-defined heterogeneous lesions within a distorted epididymis (arrowheads). (b) Photomicrographs (original magnification ×100; hematoxylin-eosin [H-E] stain) show three typical histopathologic
features: granuloma with Langerhans cells (arrow), caseation (middle *), and cystic necrosis (right *).
Figure 12. Scrotal schistosomiasis in a 28-year-old man with long-term scrotal swelling. (a) Axial US
image shows a septate fluid collection. Punctate calcifications are seen within a thickened tunica vaginalis
(arrowheads). (b) Photomicrograph (original magnification, ×250; H-E stain) shows worm eggs (arrows),
an inflammatory fibrotic reaction, and calcifications.
ple calcifications, and an enlarged tunica with diffuse or nodular disease (Fig 12). These features
arise from the host’s immune response to worm
eggs and a granulomatous inflammatory reaction
to egg antigens deposited in the tunica vaginalis.
Because the imaging findings often are nonspecific, an incisional biopsy may be necessary to
confirm the diagnosis (12).
Noninfectious
Inflammatory Disorders
Acquired Hydrocele
A minimal amount of fluid normally is present between the parietal and visceral layers of the tunica
vaginalis. An abnormal amount of fluid between
the two layers surrounding the testis is called a
hydrocele, the most common cause of scrotal
enlargement. Acquired hydrocele may form as
a reaction to tumor, infection, or trauma. It also
may be idiopathic, resulting from excessive fluid
production or failure of the mesothelial lining to
reabsorb the fluid. At US, an anechoic fluid collection is seen surrounding the testis; the collection
may contain septa, calculi, and scattered echoes
caused by protein or cholesterol content (Fig 13)
(5,13). A massive hydrocele exerts a pressure effect
mimicking that in testicular torsion and may compromise blood flow within the testis. Vascular resistance in intratesticular arteries is increased, and
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Figure 13. Recurrent hydrocele in a 58-year-old man
after sclerotherapy. Axial US image shows a multicystic
hydrocele (arrowheads).
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Figure 14. Scrotal pearl in a 35-year-old man with
abnormal scrotal pain. Longitudinal US image shows
a giant pearl and multiple cholesterol crystals within
a hydrocele.
color Doppler US may demonstrate an increase in
the caliber of capsular arteries (14). Aspiration of
the fluid restores normal blood flow to the testis.
Scrotal Calculi
Scrotal calculi are freely mobile calcified bodies
that lie between the layers of the tunica vaginalis.
Their cause is unclear. They have been seen as
a sequela to hematoma, inflammatory changes
within the scrotum, or loose bodies from a
twisted epididymal or testicular appendix (15).
The physiopathologic characteristics of scrotal
calculi are related to an inflammatory or microtraumatic factor that causes damage to the
layers of the tunica vaginalis and obstruction of
the lymphatic vessels. Abnormal reabsorption of
cholesterol, calcium, fibrin, and hydroxyapatite
results in calculus formation. Repeated deposition leads to the formation of a larger, rounded
stone that resembles a scrotal pearl (Fig 14). This
hypothesis is supported by the results of histologic studies of multiple calculi associated with
chronic inflammation and fibrosis of the tunica
vaginalis. It also implies a probable overlap between scrotal calculi and fibrous pseudotumor
(15). Scrotal calculi are easily identified at US
because the calcifications are hyperechoic and
create a discrete acoustic shadow, or “comet-tail”
Figure 15. Scrotal calculi in a 50-year-old cyclist
with scrotal discomfort. Longitudinal US image shows
multiple small echogenic cholesterol calculi attached to
the parietal layer (arrowheads), with the characteristic
comet-tail artifact.
artifact. Scrotal calculi may be attached to a normal or thickened tunica vaginalis (Fig 15).
Fibrous Pseudotumor of the Scrotum
Scrotal fibrous pseudotumors are uncommon and
are thought to be reactive, nonneoplastic lesions
(16). They are the second most common paratesticular mass, after adenomatoid tumor, and they
may mimic a malignancy clinically. US is useful
for identifying a fibrous pseudotumor, and local
excision is the treatment of choice. Although ex-
Teaching
Point
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Figure 16. Multinodular fibrous pseudotumor in a 45-year-old man with a 2-year history of a
palpable and irregular left scrotal mass. (a) Longitudinal US image shows multiple and confluent nodules (arrows) of various sizes arising from the tunica vaginalis and growing into the cavity.
A reactive hydrocele (H) surrounds the testis (T). (b) Photomicrograph (original magnification,
×150; H-E stain) shows collagen bands in a storiform pattern with small vessels (arrow).
Figure 17. Solitary fibrous pseudotumor in a 57-yearold man with a history of sclerotherapy for a hydrocele.
Longitudinal US image shows a focal area of hyperechogenicity arising from the parietal vaginal layer.
planations of the pathogenesis of fibrous pseudotumors are confusing and controversial, it is
generally accepted that these lesions represent a
benign reactive proliferation of inflammatory and
fibrous tissue, probably in response to chronic irritation. Most patients have a history of trauma,
surgery, infection, or inflammation. A rare association with S haematobium infection has been
reported, which may explain the similarity in US
findings in the two disorders (17,18).
At histologic analysis, a fibrous pseudotumor is composed of dense fibrous tissue with
interspersed fibroblasts and mixed inflammatory cells. The variation between the gross and
microscopic appearances has led to the adoption
of numerous terms to describe these lesions. A
nodular type and a diffuse type may be distinguished on the basis of gross appearance; however, these two types also may coexist. A rarer
type is inflammatory pseudotumor of the paratesticular lymph nodes (16,18,19).
The nodular type is the most common type
of fibrous pseudotumor. The typical gross appearance is that of a fibrous nodule or nodules
arising from the tunica vaginalis (76% of cases);
in the remainder of cases, nodules arise from the
epididymis, spermatic cord, or tunica albuginea.
At US, multiple nodules (Fig 16) or a single
nodule (Fig 17) are seen arising from the tunica
vaginalis, a finding usually associated with hydrocele. The nodules may appear hypoechoic or hyperechoic, depending on the amount of collagen
or fibroblast content (20). Shadowing may occur
in the absence of calcification, a finding that presumably is due to the dense collagen component
in the lesion. A small to moderate amount of
vascularity may be seen within the lesion at color
Doppler US (17).
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Figures 18, 19. Diffuse fibrous pseudotumor. US
images in two patients show different stages of the
disorder. (18) Longitudinal color Doppler US image
in a 30-year-old man with an irregular but nontender
scrotum at palpation shows thickening of the tunica
vaginalis and a few calcifications indenting the contour of the testis. Vascularity also is seen within the
area of inflammation (arrow). (19a) Longitudinal
US image in a different patient with a history of left
scrotal firmness and irregularity shows multiple calcified plaques (arrows) and clear encasement of the
testis. (19b) Photograph of the resected specimen
shows infiltrative and nodular lesions (arrowheads)
that almost completely encase the testis (T) and
paratesticular structures (*).
Diffuse fibrous pseudotumor, also called fibromatous periorchitis, is a rare variant form of
diffuse proliferative encasement of the testis that
manifests as an indurated testis and is suggestive
of malignancy. At US, thickening of the inner surface of the tunica vaginalis is seen, with focal linear calcification and ossification that indents and
partially obscures the adjacent testis. Whereas a
nodular pseudotumor may be treated with excision of the tunica vaginalis, the diffuse form often
requires radical orchiectomy (Figs 18, 19).
Inflammatory pseudotumor of the paratesticular lymph nodes is a rare form of the same
disorder. A benign cause of lymphadenopathy,
inflammatory pseudotumor has been described
as arising in several anatomic locations. The rich
network of paratesticular lymph nodes also may
be affected by this proliferation of spindle cells,
small vessels, and inflammatory cells, characteristics that simulate a malignant neoplasm (19). At
US, a predominantly hypoechoic lymph node is
seen, with low echogenicity resulting from spindle
cell proliferation in the connective tissue framework of the hilum and capsule, while the nodal
architecture is maintained (Fig 20).
Traumatic Disorders
The primary traumatic disorder affecting the
tunica vaginalis is hematocele. Other entities,
such as scrotal calculi, fibrous pseudotumor, and
scrotal tunical cysts, also may be related to a history of microtrauma but are described in other
sections of the article because they have other
primary causes.
A hematocele is an accumulation of blood
within the tunica vaginalis and may be acute or
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Figure 20. Fibrous pseudotumor of a paratesticular lymph node in a young man. (a) Longitudinal color
Doppler US image shows a nodular and lobulated, isoechoic to hypoechoic lesion with marked vascularity adjacent to the tunica vaginalis. (b) Photomicrograph (original magnification ×250; H-E stain) shows
dense connective tissue, infiltration of plasma cells, and lymphoid follicles (arrowheads).
Tumors
Primary tumors of the tunica vaginalis are uncommon. However, the mesothelial cells of the
tunica vaginalis may give rise to adenomatoid
tumor, mesothelioma, or benign intraepithelial
cyst. Other rare primary tumors of the tunica
vaginalis include benign and malignant mesenchymal tumors, lymphomas, and serous borderline tumors (2).
Adenomatoid Tumor
Figure 21. Hematocele. Axial US image shows a
complex fluid-filled mass with septa that is located
caudad to the testis.
chronic. Possible causes include trauma, torsion,
tumor, and surgery. At initial US examinations, a
recently formed hematocele is slightly echogenic.
Over time, its appearance becomes more complex, with septa, fluid-fluid levels, and echogenic
debris indicative of clots. If a hematocele becomes chronic, it may appear as a heterogeneous
encapsulated lesion that may calcify and create
a mass effect over the contour of the testis. Most
hematoceles resolve with conservative therapy, although chronic complex hematoceles may require
surgical management (Fig 21) (2,21).
Adenomatoid tumor is the benign mesothelial
tumor most commonly found in the paratesticular structures. It usually affects the epididymis
and, less commonly, the tunica vaginalis (6).
The histogenesis of adenomatoid tumors is controversial. It has been suggested that they derive
from vascular endothelium, the mesonephros,
or müllerian epithelium, although most recent
reports consider them to be mesothelial in origin
(22). An adenomatoid tumor typically manifests
as a hard painless mass that is incidentally discovered at physical examination. After excision,
gross examination reveals a hard, homogeneous,
yellow-white nodule with a smooth surface. At
microscopic analysis, the lesion is composed of
irregular tubules lined with flattened and cuboidal epithelioid or endothelioid cells that are well
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Figure 22. Adenomatoid tumor. (a) Longitudinal US image shows a well-defined isoechoic
ovoid paratesticular lesion (arrow), a finding indicative of an adenomatoid tumor arising from
the tunica vaginalis (T). (b) Photomicrograph (original magnification, ×250; H-E stain [inset,
×400; calretinin stain]) shows mesothelial cells (arrows), which characteristically are seen with
calretinin stain (inset), and isolated cystic areas (arrowheads).
recognized with calretinin staining. The stroma
consists of hyalinized or loose collagen with varying amounts of smooth muscle and elastic fibers
(22). The growth pattern of the lesion results in
an indentation of the testicular contour. An anechoic focus may be present, a finding indicative
of cystic change (Fig 22). When an adenomatoid
tumor invades the testis, it may be difficult to differentiate it from a malignant intratesticular tumor (23). Intraoperative histologic analysis may
be required to avoid unnecessary orchiectomy.
Scrotal Tunica Cyst
A scrotal tunica cyst is a relatively uncommon
benign intraepithelial mesothelial lesion that
usually manifests as a palpable testicular lump.
Such cysts may occasionally become larger. Most
tunica cysts develop from the tunica albuginea
in a subcapsular location, but they may arise
from layers of the tunica vaginalis. Their cause
is unknown, although often there is a history
of trauma, hemorrhage, or infection (6). At microscopic analysis, they are lined by nonciliated
cuboidal cells, and they contain serous fluid and
cellular debris (24). When they do not manifest
as a palpable mass, they often are discovered incidentally at US, which typically depicts a small
(2–5-mm) anechoic uni- or multilocular lesion
within the layers of the tunica vaginalis. Larger
cysts may compress the testicular parenchyma
and simulate an intratesticular lesion. Cysts may
display low-level echoes, a less common finding
indicative of debris, or calcifications with acoustic
shadowing (Figs 23, 24) (24,25).
Mesothelioma
Mesothelioma is a rare tumor that arises in
body cavities lined by mesothelium. It usually
involves pleura, peritoneum, and, less frequently,
pericardium. The tunica vaginalis, as a layer of
reflected peritoneum, also is a potential site of
mesothelioma. Although trauma, herniorrhaphy,
and long-term hydrocele have been considered
predisposing factors for development of scrotal
mesothelioma, the only well-established risk factor is exposure to asbestos (26). Mesotheliomas
are divided into subgroups according to their
histologic features. The benign forms of mesothelioma and other mesothelial lesions such as
adenomatoid tumor have similar characteristics;
however, benign forms such as reactive mesothelial hyperplasia and well-differentiated papillary
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Garriga et al 2029
Figures 23, 24. Scrotal tunica cyst. (23) Color
Doppler US image shows a typical small subcapsular
cyst (arrowhead) of the tunica albuginea. (24a) US
image of a different patient shows a large, sharply
demarcated cyst with low-level internal echoes.
(24b) Photomicrograph (original magnification,
×250 [inset, ×450]; H-E stain) shows that the cyst is
lined by flattened cells (arrowheads).
mesothelioma are less common than their malignant counterparts (2,27).
At microscopic analysis, mesothelioma consists
of complex papillary fronds lined by cuboidal,
bland-looking nuclei with eosinophilic cytoplasm.
The criteria for malignancy are nuclear pleomorphism, mitotic activity, and stromal invasion (28).
Mesotheliomas may have the gross appearance of
nodules or papillary excrescences or may occur in
an infiltrative pattern that is much more difficult to
recognize (29). Local invasion of subtunical tissue
and testis is seen in 50% of patients, whereas the
epididymis, scrotal skin, and vascular structures
are less commonly involved (30). The nonspecific
symptoms, broad age distribution, and lack of tumor markers make preoperative diagnosis difficult;
a diagnosis of mesothelioma is not usually made
until surgery is performed.
A malignant mesothelioma should be suspected in a patient with a progressively enlarging
hydrocele and rapid re-accumulation of fluid after aspiration. Various US appearances have been
reported. A hydrocele, either simple or complex,
typically is seen and may be associated with wellorganized soft-tissue fronds of mixed echogenicity,
with a hypoechoic center surrounded by a hyperechoic rim or multiple extratesticular hyperechoic
nodules arising from the tunica vaginalis. USguided fine-needle aspiration of solid masses is
recommended when cytologic analysis of fluid is
negative (30). Less often, mesothelioma may appear as thickening of the tunica vaginalis with or
without epididymal involvement (26). At color
Doppler US, hyperemia of the involved tunica
vaginalis is seen (Fig 25) (30). Because this is an
aggressive tumor, surgical treatment with radical
orchiectomy is necessary (3).
Teaching
Point
2030 November-December 2009
radiographics.rsna.org
Figure 25. Scrotal mesothelioma in a 55-year-old man with a history of an enlarging and recurrent hydrocele. (a) Longitudinal US image shows a large hydrocele with an isoechoic pediculated excrescence arising
from the tunica vaginalis cavity. (b) Color Doppler US image shows that the underlying tunica vaginalis is
thickened and hyperemic.
Lipoma and Leiomyoma
Benign mesenchymal tumors of the scrotum
are rare. Although they usually originate from
the epididymis or spermatic cord, they also may
originate from the tunica vaginalis. Cases of lipoma and leiomyoma that arise from the tunica
vaginalis and manifest as a painless scrotal mass
have been reported. At US, lipomas tend to be
well-defined, homogeneous, and hyperechoic,
although a hypoechoic or heterogeneous echotexture may be seen in the presence of fibrous,
myxoid, or vascular tissue (Fig 26) (2). Leiomyoma is a smooth muscle tumor characterized by interlacing bundles of spindle-shaped
muscle cells that also may demonstrate myxoid
degeneration. At gross sectioning, the tumor is
white-gray and encapsulated. At US, the appearance varies, depending on whether the tumor is
predominantly solid or cystic. An echo pattern of
multiple narrow areas of shadowing, which are
not cast by calcifications but instead correspond
to transition zones between the various tissue
components of the mass, and a whorl-shaped
echo pattern also are characteristic of leiomyoma
and may help differentiate it from other scrotal masses (31). Leiomyoma may or may not
contain shadowing due to calcifications. In the
Figure 26. Scrotal lipoma. Axial US image obtained
in a 68-year-old man with a painless scrotal mass shows
a uniformly lobulated, well-defined isoechoic to hyperechoic mass, findings indicative of a lipoma.
absence of such findings, leiomyoma may be
indistinguishable from adenomatoid tumor and
fibrous pseudotumor (18,31).
The US appearances of both lipoma and leiomyoma are far from specific, and an intraoperative biopsy with simple excision of the tumor is
necessary to achieve a definitive diagnosis allowing appropriate surgical treatment.
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Garriga et al 2031
Figure 27. Sclerosing scrotal liposarcoma in a 52-year-old man with a palpable
abnormality in the right scrotum. (a) Axial US image shows an extratesticular lesion (arrows) distorting the testis (T). (b) Axial color Doppler US image shows
the heterogeneous echotexture of the tumor. Focal hypoechoic necrosis and
marked hyperemia also are seen.
Sarcomas
Sarcomas are uncommon malignant tumors that
originate from mesenchymal cells entrapped
within the spermatic cord, epididymis, or tunica.
Most arise just below the superficial inguinal
ring and develop into a scrotal mass involving
paratesticular structures. Rhabdomyosarcoma is
the most common type in pediatric patients, and
it has a very aggressive growth pattern. At US, a
heterogeneous and hypervascular mass is seen,
often with invasion of the scrotum and extension
into the inguinal region. A hydrocele also may
be seen (32,33).
Liposarcoma and leiomyosarcoma are the most
common sarcomas in adults (2). At US, a solid
heterogeneous mass is seen with hypoechoic areas
due to hemorrhage and necrosis (Fig 27). Calcifications and hydrocele also may be seen (34) .
US is helpful for demonstrating an extratesticular
origin of the neoplasm and evaluating the inguinal
lymph nodes; however, the pattern seen at US
does not allow definitive characterization of the tumor, and surgical biopsy is necessary. Radical surgery is the only effective treatment for sarcomas,
with the exception of rhabdomyosarcoma, which
responds to radiation and chemotherapy (35).
Lymph node involvement is seen in one-third of
paratesticular sarcomas. In patients with lymph
node involvement, pelvic lymph node dissection
and radiation therapy are indicated, in addition to
radical orchiectomy (34).
Conclusions
Most scrotal lesions occur in paratesticular tissue,
many in the tunica vaginalis. Their significance
and clinical management may pose a therapeutic
dilemma because many, but not all, are benign.
Knowledge of the anatomic relationships and
pathologic disorders involving the tunica vaginalis
is essential to narrow the differential diagnosis of
an extratesticular lesion. An understanding of the
embryologic development of the tunica vaginalis,
knowledge of the patient’s age at presentation,
and a thorough physical examination are useful
for diagnosis of congenital lesions. Clinical assessment is essential to guide the diagnosis of infectious, inflammatory, and traumatic disorders,
and follow-up US to document lesion stability or
treatment response can help avoid unnecessary
surgery. Only some US features can help correctly identify tumors; the nonspecific nature of
most findings in the tunica vaginalis and scrotum
often make it impossible to rule out malignancy
at US. However, knowledge of the US findings
is helpful for planning the best surgical approach
and deciding whether to perform local excision
with testicle-sparing surgery or orchiectomy.
2032 November-December 2009
Acknowledgments: The authors thank Jordi Puig
for technical assistance and John Giba for linguistic
support.
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This article meets the criteria for 1.0 AMA PRA Category 1 Credit TM. To obtain credit, see www.rsna.org/education
/rg_cme.html.
RG
Volume 29 • Number 5 • November-December 2009
Garriga et al
US of the Tunica Vaginalis Testis: Anatomic Relationships and
Pathologic Conditions
Victoria Garriga, MD, et al
RadioGraphics 2009; 29:2017–2032 • Published online 10.1148/rg.297095040 • Content Codes:
Page 2018
The tunica vaginalis is a mesothelium-lined sac that results from closure of the superior portion of the
processus vaginalis. This fascial structure normally covers the entire testis except the posterior border.
It has a visceral layer and an outer parietal layer that lines the internal spermatic fascia of the scrotal
wall.
Page 2019
Incomplete closure of the processus vaginalis leads to a variety of abnormalities. Complete patency of
the processus vaginalis may result in a communicating hydrocele or a congenital inguinoscrotal
hernia. Incomplete atresia of the funicular process may result in a funicular or encysted hydrocele of
the cord.
Page 2022
In advanced scrotal tuberculosis, US depicts epididymo-orchitic or vaginal nodules without flow,
findings indicative of tuberculomas with cystic necrosis. These nodules may be the only US finding of
tunica vaginalis involvement, and the testis and epididymis may remain intact.
Page 2024
Scrotal fibrous pseudotumors are uncommon and are thought to be reactive, nonneoplastic lesions.
They are the second most common paratesticular mass, after adenomatoid tumor, and they may
mimic a malignancy clinically. US is useful for identifying a fibrous pseudotumor, and local excision
is the treatment of choice.
Page 2029
A malignant mesothelioma should be suspected in a patient with a progressively enlarging hydrocele
and rapid re-accumulation of fluid after aspiration. Various US appearances have been reported. A
hydrocele, either simple or complex, typically is seen and may be associated with well-organized softtissue fronds of mixed echogenicity, with a hypoechoic center surrounded by a hyperechoic rim or
multiple extratesticular hyperechoic nodules arising from the tunica vaginalis. US-guided fine-needle
aspiration of solid masses is recommended when cytologic analysis of fluid is negative. Less often,
mesothelioma may appear as thickening of the tunica vaginalis with or without epididymal
involvement. At color Doppler US, hyperemia of the involved tunica vaginalis is seen. Because this is
an aggressive tumor, surgical treatment with radical orchiectomy is necessary.