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Sonography of
Scrotum and
Testes
.
Anatomy
The scrotum is divided by the midline raphe. Each half of the
scrotum contains a spermatic cord, testis, and epididymis. The
testes descend into the scrotum at approximately the 28th
gestational week via the inguinal canal through the peritoneal
recess, which is called the processus vaginalis. The processus
vaginalis gradually closes through infancy and childhood. The testis
is covered by a visceral layer of tunica vaginalis, except where in
contact with epididymis, and by the tunica albuginea. The posterior
surface of the tunica albuginea extends into the testis to form the
mediastinum testis. This is seen as a middle echogenic line on
longitudinal US of the testis The testis has lobules containing the
seminiferous tubules. Testicular lobules are occasionally identified
as lines radiating from the mediastinum testis
The size and shape of the testes change with age. •
Testicular size is influenced by gonadal hormones. In boys,
from birth to 5 months of age, the testicular volume rises
to a maximum of 0.44 (±0.03) cm3. The rise in testicular
volume coincides with a peak in gonadotropic hormones,
so-called minipuberty, at approximately 3 to 4 months of
age.
After age 5 months, the testicular volume steadily
declines and reaches its minimum volume at
approximately 9 months of age and remains
approximately the same size until puberty.
The testis is rounded in newborns and gradually becomes
ovoid with growth.
The epididymis has three parts: head, body, and tail. In •
the normal epididymis, only the head is routinely
identified. The epididymal head is located in the upper
pole of the scrotum, is triangular in shape, and has the
same echogenicity as the testis.
Testicular appendixes are remnants of the mesonephric •
and paramesonephric ducts. They can be identified by
US in cases of hydrocele
The spermatic cord appears as an echogenic band on •
longitudinal images and ovoid on transverse images as it
passes in the inguinal canal. Color Doppler shows the
testicular artery and pampiniform venous plexus .In the
inguinal canal, the normal thickness of the spermatic
cord is up to 4 mm. The normal inguinal canal does not
contain fluid.
Ultrasound (US) is a readily available and relatively
inexpensive imaging modality that can be performed on
patients at any age without the need for sedation or any
other pretest preparation. US examinations are safe and
there is no significant biologic risk from radiation
exposure.
Different pathologies of the scrotum may have similar
clinical presentation, such as acute scrotal pain or scrotal
mass. US of the scrotum can better guide treatment by
improving the definition of the scrotal pathology. For
these reasons, US became the imaging modality of choice
for evaluation of scrotal pathology, and, in most cases, US
is the first and only imaging needed for evaluation of
scrotal pathology.
Color Doppler demonstrates capsular •
and intratesticular vessels.
In prepubertal testes, it can be difficult
to detect intratesticular flow, but the
capsular arteries are easier to identify. It
is, however.
The resistive index of the intratesticular •
arteries changes with age from high to
low resistive index
Indications for Scrotal Ultrasound
Pain: trauma, inflammation, torsion
Mass: testicular, extratesticular
Evaluation of a possible hernia and its contents
Search for occult neoplasm in cases of retroperitoneal or
mediastinal lymphadenopathy
Follow-up of previous infections, tumors, lymphoma,
leukemia
Small testes, atrophy
Location of undescended testes
Infertility
Precocious puberty or feminization
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The acute scrotum •
Acute scrotal pain is a medical urgency as 12% to 26% of
boys who have it have testicular torsion. The main
differential diagnosis includes testicular torsion, torsion of
appendix testis, and epididymitis.
It is crucial to rapidly diagnose testicular torsion because
prognosis of the testis depends on the duration of
torsion.[Ischemia of the testis can be reversible in the first
6 hours.[US is typically required when the clinical
assessment is equivocal for testicular torsion. Testicular
torsion typically presents as an acute, excruciating scrotal
pain of short duration before a patient arrives in the
emergency room. Physical examination typically reveals
diffuse tenderness, abnormal high and horizontal position
of the testis, and absence of the cremasteric reflex.
Gray-scale findings of testicular torsion may be normal. Testicular
gray-scale abnormalities include testicular swelling or heterogeneous
or decreased testicular echotexture.
Heterogeneous parenchymal echotexture usually indicates testicular
nonviability. Other findings include swelling of the epididymis,
hydrocele, and scrotal skin edema .Epididymal swelling is common in
testicular torsion and, in a few cases, associated with increased
epididymal flow.
A gray-scale study should include evaluation of the spermatic cord.
A coiled spermatic cord could be the only sign for testicular torsion
as perfusion of the testis can be normal in partial torsion (<360°) or
even increased in a case of torsion-detorsion. Evaluation of the
spermatic cord increases the sensitivity for detection of testicular
torsion.
Decreased testicular blood flow on a color Doppler study •
is the most sensitive finding that indicates testicular
torsion. Testicular capsular blood flow may increase and
erroneously suggest, in young boys, the presence of
testicular perfusion. Therefore, prudent examination of
intratesticular blood flow is necessary.
Spectral evaluation of the blood flow and •
documentation of venous and arterial wave flow are
important. Initially, only venous flow may be absent.
Comparing the intratesticular flow to the contralateral
testis is important, as any decrease in perfusion or
change in the waveform may be the first indication of
testicular torsion
Acute torsion of the testis
Rates of testicular salvage by time from start of symptoms.
Davenport, M. BMJ 1996;312:435-437
Copyright ©1996 BMJ Publishing Group Ltd.
Torsion of Testicular Appendix
The appendix testis, a müllerian duct remnant located at the
superior pole of the testicle, is the most common appendix to twist.
The epididymal appendix, located at the head of the epididymis, is a
wolffian duct remnant.
Torsion of testicular appendix can occur at any age but is most
common between the ages of 7 and 12 years. The pain is typically
indolent and not as severe as the pain from testicular torsion.
Duration of scrotal pain is significantly longer than that of testicular
torsion. A palpable tender nodule in the upper pole of the scrotum
and the blue dot sign, which represents the bluish discoloration of
the torsed appendix, are specific signs for torsion of testicular
appendix.
US typically demonstrates an extratesticular nodule with no
vascularity in the upper pole of the scrotum. The maximal diameter
of the torsed appendix varies from 4 to 16 mm. There may be an
overlap between the size of torsed and normal appendixes when
the nodule is smaller than 6 mm.
The torsed appendix leads to secondary inflammation in
the surrounding structures. The epididymis is almost
always swollen with increased perfusion, and occasionally
there is swelling and increased perfusion of the testis.
Other findings include scrotal wall edema and hydrocele.
In some cases, when the torsed appendix is not identified
by US, the findings cannot be distinguished from acute
epididymitis.
Treatment includes analgesic and anti-inflammatory
medications. Surgery is reserved for patients in
excruciating pain who are not responding to medication or
when it is not possible to clinically distinguish from
testicular torsion.
Scrotal appendages. (A) Appendix testis. (B) Appendix epididymis originating
from the surface of an epididymal cyst. Both appendages are seen because of thepresence of
peritesticularfluid. Arrow, appendages. EC, epididymal cyst
Torsed appendix testis.enlarged avascular
appendix testis surrounded by increased blood flow
Acute Epididymitis •
Epididymitis is an inflammation of the epididymis. Epididymitis is
described in response to infection, trauma, vasculitis, or urine
refluxing into the ejaculatory ducts but in most cases is
idiopathic.The diagnosis is often based on clinical presentation of a
few days of acute scrotal pain, swelling, and tenderness of the
epididymis.
Presentation in young boys and those with recurrent epididymitis
should lead to further evaluation with renal US and
cystourethrography for associated anomalies. Anomalies that are
described in association with epididymitis include ectopic ureter to
the seminal vesicles and lower urinary tract anomalies, such as
recto-ureteral fistula and strictures of the urethra. Recurrent
epididymitis can also occur in boys with neurogenic bladder or
functional bladder abnormalities.
Gray-scale US findings of epididymo-orchitis include an
enlarged epididymis. The echotexture of the epididymis
varies, depending on time of evolution, from decreased
to increased echogenicity.
Inflammation of the testis, orchitis, is confirmed by
enlarged testis with heterogeneous echotexture. Indirect
signs of inflammation, such as reactive scrotal wall
edema and hydrocele, are present in most cases.
Duplex US demonstrates hyperemia of the epididymis
and, when orchitis is present, increased testicular
perfusion.
Acute epididymitis
Epididymo-orchitis