Diagnostic ultrasound ( PDFDrive )

CHAPTER 22 The Scrotum 851
sonography can assess for viability of the testis in the setting of
penetrating trauma. A careful gray-scale and color low Doppler
evaluation of the epididymis should be performed in all examinations
of blunt trauma. Traumatic epididymitis may be an isolated
inding that should not be confused with an infectious process. 204
CRYPTORCHIDISM
he testes remain near the deep inguinal ring until the seventh
month of gestation when they normally begin their descent
through the inguinal canal into the twin scrotal sacs. 1,2 he
gubernaculum testis is a ibromuscular structure that extends
from the inferior pole of the testis to the scrotum and guides
the testis in its descent, a process normally completed before
birth. Undescended testis is one of the most common genitourinary
anomalies in male infants. At birth, 3.5% of male infants
weighing more than 2500 g have an undescended testis; 10% to
25% of these cases are bilateral. his igure decreases to 0.8% by
age 1 year because the testes descend spontaneously in most
infants. he incidence of undescended testes increases to 30%
in premature infants, approaching 100% in neonates who weigh
less than 1000 g at birth. Complete descent is necessary for full
testicular maturation. 205,206
Malpositioned testes may be located anywhere along the
pathway of descent from the retroperitoneum to the scrotum.
Most (80%) undescended testes are palpable, lying distal to the
external inguinal ring. Anorchia occurs in 4% of the remaining
patients with impalpable testes. 206
Localization of the undescended testis is important for the
prevention of two potential complications of cryptorchidism:
infertility and cancer. he undescended testis is more likely to
undergo malignant change than is the normally descended testis. 3
he most common malignancy is seminoma. he risk of malignancy
is increased in both the undescended testis ater orchiopexy
and the normally descended testis. herefore careful serial
examinations of both testes are essential.
Sonographically, the undescended testis is oten smaller and
slightly less echogenic than the contralateral, normally descended
testis (Fig. 22.36). he pars infravaginalis gubernaculi, which is
the distal bulbous segment of the gubernaculum testis, can be
FIG. 22.36 Testis in Inguinal Canal. Longitudinal scan shows an
elongated, ovoid, undescended testis.
mistaken for the testis. Ater completion of testicular descent,
the pars infravaginalis gubernaculi and the gubernaculum
normally atrophy. If the testis remains undescended, both
structures persist. he pars infravaginalis gubernaculi is located
distal to the undescended testis, usually in the scrotum, but it
may be found in the inguinal canal. Sonographically, the pars
infravaginalis gubernaculi is a hypoechoic, cordlike structure of
echogenicity similar to the testis, with the gubernaculum leading
to it. 207
Sonography is oten used in the initial evaluation of cryptorchidism,
although the value of this has been questioned because
it is insensitive in detecting high intraabdominal testes. 208 MRI
has also been used in cryptorchidism because it is more sensitive
than ultrasound in detecting undescended testes in the retroperitoneum.
209,210 Nonvisualization of an undescended testis on
sonography or MRI does not exclude its presence, and therefore
laparoscopy or surgical exploration should be performed if
clinically indicated.
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