Cryptorchidism is defined as the absence of one or both testicles from the scrotum, and the incidence of congenital cryptorchidism in full-term males is estimated at 2% to 4%.7
Testicles originate in the high retroperitoneum; therefore, ultrasound evaluation for undescended testicles must extend from below the liver and spleen, inferiorly through retroperitoneum and inguinal canals, to the scrotum (Fig. 18.4
). Multiple risk factors have been implicated for causing undescended testicles, including prematurity and multiple maternal factors/exposures; however, no single etiology stands out.8
If undescended testicles are occult to ultrasound, MRI may be helpful, particularly using T2-weighted and diffusion-weighted sequences where they appear hyperintense (Fig. 18.4
). The undescended testicle has a higher risk of malignancy (especially seminoma), and it is unclear whether this risk is decreased with surgical repair.11
Ambiguous External Genitalia
Ambiguous external genitalia can be a source of great concern and require a multidisciplinary approach to determine the correct diagnosis. The currently accepted term for the spectrum of etiologies is “disorders of sex development” (DSD). It should be noted that not all DSD manifests as ambiguous external genitalia. In the absence of the Y chromosome, the internal and external genitalia develop the “default” female phenotype.
Ultrasound workup of ambiguous genitalia must include evaluation of scrotum/labia, inguinal canals, pelvis, kidneys, and adrenal glands. As shown in Table 18.1
, identification of the uterus and characterization of both gonads are critical to classifying the DSD. The most common cause of ambiguous genitalia is congenital adrenal hyperplasia, which is one of the several causes of female pseudohermaphroditism (46,XX).12
In congenital adrenal hyperplasia, the adrenal glands are often enlarged with a “cerebriform” appearance. The most common cause of ambiguous genitalia with a 46,XX genotype is androgen insensitivity syndrome, which is one of the several causes of male pseudohermaphroditism.12
In complete androgen insensitivity (Fig. 18.4
), the external genitalia are female, whereas in partial androgen insensitivity, the external genitalia are ambiguous. In some children, DSD may be very complex, requiring MRI evaluation and a systematic interdisciplinary approach to fully classify and characterize the disorder (Fig. 18.5
Adrenal Cortical Rests/Testicular Adrenal Rest Tumors (TARTs)
Heterotopic adrenal cortical tissue can be found in the paratesticular region and sometimes within the testicle. Intratesticular adrenocortical tissue can proliferate into tumor-like masses in patients with congenital adrenal hyperplasia, and Nelson syndrome can sometimes present with detectable intratesticular masses at ultrasound both during childhood and adulthood.13
The adrenal tissue becomes trapped in the testicles in utero prior to migration from the high retroperitoneum and subsequently enlarges in response to elevated adrenocorticotropic hormone.
Although their ultrasound appearance can be variable, these rests most often present as one or more bilateral intratesticular hypoechoic masses (Fig. 18.6
Testicular venous sampling for elevated cortisol levels may confirm the diagnosis.16
FIGURE 18.4 A: A 9-year-old boy with undescended testicle. Longitudinal gray-scale ultrasound image shows that the right testicle (arrows) is located in the upper portion of the right inguinal canal and contains diffuse microlithiasis. The testicle is located superficial to gas-containing bowel loops (asterisks). B—E: A 15-year-old phenotypic girl presents with amenorrhea. Coronal T2-weighted fat-saturated MR images show hyperintense undescended testicles (arrows) along the right pelvic sidewall and in the left inguinal region, respectively. The gonads are markedly hyperintense on diffusion-weighted MR imaging. Genetic workup revealed XY sex chromosomes and 17-beta hydroxylase deficiency. (Images B—E courtesy of Jonathan R. Dillman, MD, MSc, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH. Reprint with permission from J Pediatr Adolesc Gynecol. 2016 Dec;29(6):577—581.)
Splenogonadal fusion is a rare cause of an extratesticular mass that results from the migration of splenic tissue with the testicle.17
The connection may be direct
(continuous) with the principle spleen fused to the intrascrotal testicle or indirect
(discontinuous) with independent (ectopic) splenic tissue traveling into the scrotum with the testicle. Although the involved splenic tissue should have similar imaging features of native spleen at ultrasound, CT, and MRI (Fig. 18.7
), there may be overlap in appearance with the testicle. Although scintigraphy (99m
Tclabeled sulfur colloid or damaged red blood cells) could potentially help in the diagnosis,18
splenogonadal fusion is rare; therefore, most patients go on to surgery for removal of a scrotal mass and the diagnosis is confirmed by histopathology.
TABLE 18.1 Disorders of Sex Development
Persistent Mullerian duct syndrome
Female or ambiguous
Female or ambiguous
Mixed gonadal dysgenesis
46,XY or 45,XO
Testis and streak
Pure gonadal dysgenesis
Testis and ovary, or ovotestis
Disorders of Sex Development can be classified using imaging based on presence/appearance of the gonads and uterus. Adapted from Chavhan G, Parra D, Oudjhane K, et al. Imaging of ambiguous genitalia: classification and diagnostic approach. Radiographics. 2008;28(7):1891-1904.
FIGURE 18.5 A 3-month-old 46XX infant with disorder of sexual differentiation. A and B: Axial and sagittal T2-weighted MR images show a penis-like structure (arrows) with recognizable corpora. A scrotum was present at physical examination, and no perineal orifice was appreciated. C: Sagittal T2-weighted MR image shows a uterus (arrows) posterior to the bladder. D: Higher axial T2-weighted MR image shows normal-appearing ovaries (arrows) containing numerous small cysts (follicles). (Case courtesy of Jonathan R. Dillman, MD, MSc, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH.)
FIGURE 18.6 A 9-year-old boy with poorly controlled congenital adrenal hyperplasia. Longitudinal gray-scale ultrasound image shows a geographic area of decreased echogenicity (arrows) in the central left testis, consistent with an adrenal rest.
Bell Clapper Anomaly and Testicular Torsion
If the processus (tunica) vaginalis completely envelopes the testicle and there is failure of normal posterior anchoring of the testicle to the scrotum, the resulting configuration is called a “bell clapper” anomaly. This is because the testicle can freely swing and rotate within the processus vaginalis like a bell clapper in a bell (Fig. 18.9
). Normally, a broad base of direct testicular contact with the internal spermatic fascia prevents free mobility. Therefore, children with a bell clapper anomaly are at increased risk of intravaginal testicular torsion.20
The incidence of bell clapper anomaly has been reported to be 12% in autopsy series,21
although the frequency of torsion is far less than this22
; therefore; other factors are likely involved.
FIGURE 18.7 A 20-year-old young man with palpable scrotal mass. Axial contrast-enhanced CT image demonstrates an enhancing left extra-testicular scrotal mass (arrows) which was surgically removed and confirmed to be splenic tissue at histopathology.
FIGURE 18.8 A 13-year-old boy with palpable mass in the scrotum due to tunica albuginea cyst. Transverse gray-scale (A) and color Doppler (B) ultrasound images demonstrate a well-circumscribed, avascular, anechoic cyst (arrows) located along the surface of the testicle.
Testicular torsion is the twisting of the testicle about the spermatic cord and causes obstructed venous outflow, lack of arterial inflow, and eventual infarction of the testicle (Fig. 18.10
). The clinical presentation is most often severe acute unilateral scrotal pain, nausea, and vomiting; physical exam may reveal a high-riding horizontal testicle with an absent cremasteric reflex.23
The acute presentation should help distinguish torsion from the gradual symptom onset of epididymitis or orchitis; however, intermittent torsion may present more subacutely.24
The lack of venous outflow leads to testicular congestion (edema), and this presents at ultrasound as an enlarged testicle with decreased echogenicity and heterogeneous echotexture as well as decreased Doppler
blood flow (Fig. 18.11
). Prolonged torsion may result in a markedly enlarged, heterogeneous testicle with areas of geographic increased and decreased echogenicity. However, as abnormally decreased Doppler blood flow is only 84% sensitive for detecting torsion, normal or increased intratesticular Doppler signal should not exclude the diagnosis when clinical suspicion is high.25
Presumably, a false-negative Doppler ultrasound examination is commonly due to intermittent torsion.
FIGURE 18.9 A:
Normal posterior fixation of the testicle in the scrotum. B:
Bell clapper anomaly without torsion. Note the lack of normal posterior fixation. C:
Extravaginal testicular torsion without bell clapper anomaly. D:
Intravaginal testicular torsion with bell clapper deformity. Note that fluid is present posterior to the testicle. (Reproduced with permission from RSNA and the copyright owner.121
FIGURE 18.10 A 12-year-old boy with acute scrotal pain due to intravaginal torsion and testicular infarction. Grossly, the cut surface of the testis is red-maroon and bulging (left). Microscopically, there is hemorrhagic infarction, with extensive interstitial blood; tubular cells show cytoplasmic hypereosinophilia and nuclear pyknosis, characteristic of an evolving infarct (right, hematoxylin and eosin, original magnification, 200×).
FIGURE 18.11 An 8-year-old boy with acute testicular pain awaking him from sleep. Longitudinal color Doppler ultrasound images of the (A) right and (B) left testicles demonstrate right testicular enlargement and heterogeneity (asterisk) as well as absent blood flow, consistent with testicular torsion. The left testicle is normal.
There are two unique types of testicular torsion that occur in children. As discussed above, the bell clapper anomaly is a developmental abnormality where the testicle is inadequately affixed to the posterior scrotum, thus allowing the spermatic cord and testicle to twist within the confines of the processus (tunica) vaginalis. This type of torsion is therefore defined as intravaginal. The diagnosis of a bell clapper anomaly can be confidently made when fluid completely surrounds the testicle without the usual posterior anchoring of the gubernaculum, epididymis, and testis to the scrotum. The “torsion knot” sign may also be observed, appearing as a supratesticular mass-like abnormality, which is due to twisted, edematous spermatic cord.26
Intravaginal torsion is much more common in adolescents, whereas extravaginal torsion (described below) is more common in neonates.
Very young children (including fetuses and neonates) are susceptible to testicular torsion due to a deficient gubernaculum, which allows the testicle and processus vaginalis to twist together. This type of torsion is referred to as extravaginal, and it most often occurs in utero or soon after birth. At ultrasound, findings suggestive of extravaginal testicular infarction include a small hypoechoic testicle (frequently inguinal in location) with a calcific rim (the rim is echogenic and may show posterior acoustic shadowing) and decreased Doppler blood flow27
Treatment of testicular torsion generally requires surgery; however, there is only about a 4- to 8-hour window after onset before permanent ischemic damage occurs. Delay in treatment may result in infertility or require orchiectomy.23
In cases where a bell clapper anomaly is present, bilateral orchiopexy is performed. Based on a recent survey of practicing urologists, management of neonatal (including prenatal/perinatal) torsion is inconsistent with children undergoing surgical exploration on emergent, urgent, and elective bases.28
In the setting of neonatal torsion (when bell clapper anomaly is not the primary mechanism of torsion), many surgeons also still perform bilateral orchiopexy.28