Diagnostic ultrasound ( PDFDrive )

844 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
Torsion
Torsion is more common in adolescent boys and represents
approximately 20% of the acute scrotal pathologic phenomena
in postpubertal males. 3 Prompt diagnosis is necessary because
torsion requires immediate surgery to preserve the testis. he
testicular salvage rate is over 80% if surgery is performed within
5 or 6 hours of the onset of pain, 70% if surgery is performed
within 6 to 12 hours, and only 20% if surgery is delayed for more
than 12 hours. 159
Two types of testicular torsion have been described: intravaginal
and extravaginal. Extravaginal torsion occurs prenatally
and in newborns up to 30 days ater delivery. Torsion occurs
outside of the tunica vaginalis when the testis, gubernaculum,
and tunica vaginalis are not ixed to the scrotal wall, allowing
rotation of these structures as a unit and causing torsion of the
cord at the level of the external ring. If this occurs prenatally,
the afected neonate presents with a irm, painless mass in the
scrotum, and swelling and discoloration of the afected side. he
testis is typically infarcted and necrotic at birth. Postnatal testicular
torsion is detected as a change in the testicular examination. 160,161
Intravaginal torsion is the more common type, arising within
the tunica vaginalis and occurring most frequently at puberty.
It results from anomalous suspension of the testis by a long stalk
of spermatic cord mesentery, resulting in complete investment
of the distal cord, testis, and epididymis by the tunica vaginalis.
his allows the testis to swing and rotate within the tunica vaginalis
like a clapper inside a bell, the so-called bell-clapper
deformity (Fig. 22.29). Anomalous testicular suspension is
bilateral in 50% to 80% of patients; hence the contralateral testis
is usually ixed at the time of surgery as well. Sonography is
considered the irst step in evaluation of the acute scrotum, and
its role is well established. 162-164 Sonographic indings vary with
duration and degree of rotation. Gray-scale sonographic changes
are nonspeciic in the acute phase of torsion. 157,161,165 A torsed
testis with normal, homogeneous echogenicity on gray-scale
imaging has a high chance of successful salvage at surgery. 166
Testicular enlargement and decreased echogenicity are the most
common indings 4 to 6 hours ater the onset of torsion. With
continued torsion, at 24 hours the testis can develop heterogeneous
echotexture secondary to vascular congestion, hemorrhage, and
infarction 167-169 (Fig. 22.30). A hypoechoic or heterogeneous
echogenicity may indicate nonviability, although this is not
speciic. 166
Torsion may change the position of the long axis of the testis.
Extratesticular sonographic indings typically occur in torsion
and are important to recognize. he spermatic cord immediately
cranial to the testis and epididymis is twisted, causing a characteristic
torsion knot or “whirlpool pattern” of concentric layers
seen on sonography or MRI 161,170,171 (Fig. 22.30G and H). he
epididymis may be enlarged and heterogeneous because of
hemorrhage or ischemia, and may be diicult to separate from
the torsion knot of the spermatic cord. his spherical epididymiscord
complex can be mistaken for epididymitis. 161 A reactive
hydrocele and scrotal skin thickening are oten seen with torsion.
Large, echogenic, or complex extratesticular masses caused by
hemorrhage in the tunica vaginalis or epididymis may be seen
A
C
FIG. 22.29 “Bell-Clapper” Anomaly, Intravaginal Torsion, and
Extravaginal Torsion. (A) Normal anatomy. The tunica vaginalis
(arrows) does not completely surround the testis and epididymis, which
are attached to the posterior scrotal wall (short arrow). (B) Bell-clapper
anomaly. The tunica vaginalis (arrows) completely surrounds the testis,
epididymis, and part of the spermatic cord, predisposing to torsion. (C)
Intravaginal torsion. Bell-clapper anomaly with complete torsion of
the spermatic cord, compromising the blood supply to the testis. (D)
Extravaginal torsion in a neonate. Tunica vaginalis (arrows) is in normal
position, but abnormal motility allows rotation of the testis, epididymis,
and spermatic cord.
in patients with undiagnosed torsion. 172 he gray-scale indings
of acute and subacute torsion are not speciic and may be seen
in testicular infarction caused by epididymitis, epididymo-orchitis,
and traumatic testicular rupture or infarction.
Doppler sonography is the most useful and most rapid
technique to establish the diagnosis of testicular ischemia and
to help distinguish torsion from epididymo-orchitis. 157,162,167 he
absence of intratesticular blood low at color and power Doppler
ultrasound is considered diagnostic of ischemia (color and power
techniques appear to have equivalent sensitivity in the diagnosis
of torsion). 173-178 Meticulous scanning of the testicular parenchyma
with the use of low-low detection Doppler settings (low pulse
repetition frequency, low wall ilter, high Doppler gain, small
color sampling box, lowest possible threshold setting) is important
because intratesticular vessels are small and have low low velocities,
especially in prepubertal boys. Color low Doppler sonography
is more sensitive for showing decreased testicular low in
incomplete torsion than is nuclear scintigraphy, which is rarely
B
D