Diagnostic Ultrasound - Abdomen and Pelvis

Epididymitis/Orchitis
TERMINOLOGY
Synonyms
• Acute scrotum, orchitis, epididymo-orchitis
Definitions
• Infectious inflammation of epididymis &/or testis
IMAGING
General Features
• Best diagnostic clue
○ Enlarged, hyperemic epididymis &/or testis on color
Doppler US
• Location
○ Early epididymitis often involves tail of epididymis
○ Orchitis is usually secondary, occurring in 20-40% of
epididymitis due to contiguous spread of infection
– Primary orchitis is caused by mumps and is usually
bilateral
• Size
○ Epididymis typically 2-3x larger than normal
• Morphology
○ Focal enlargement of tail or diffuse enlargement of
entire epididymis
Ultrasonographic Findings
• Grayscale ultrasound
○ Epididymitis: Primarily involved in epididymo-orchitis
– Acute: Enlarged epididymis, ↓ echogenicity, coarse
heterogeneous echotexture due to edema &
hemorrhage
– Chronic epididymitis: Enlarged hyperechoic epididymis
○ Orchitis: Follows in 20-40% of epididymitis due to
contiguous spread of infection
– Focal or diffuse
□ Focal: Hypoechoic area adjacent to enlarged
portion of epididymis
□ Diffuse: Testis is diffusely enlarged with
heterogenous echotexture, thickening of tunica
albuginea (in severe infection)
– Edematous, congested testes contained within rigid
tunica albuginea → ↑ intratesticular pressure
□ Heterogeneous parenchymal echogenicity
(predominantly hyperechoic initially and
hypoechoic later) and septal accentuation visible as
hypoechoic bands
□ May lead to venous occlusion
□ Can cause vascular compromise → ischemia →
testicular infarction → sonographic features
indistinguishable from testicular torsion ( flow
preserved in epididymis compared to torsion where
flow is absent in both testis and epididymis)
○ Spermatic cord may be inflamed and may appear
hypoechoic with associated hyperechoic fat within
○ Reactive hydrocele containing low-level internal echoes,
septae, thickening of tunical layers ± skin edema; all
represent changes of periorchitis
• Color Doppler
○ Diffuse or focal hyperemia in body and tail of epididymis
± increased vascularity of testis → highly sensitive and
specific for epididymo-orchitis
○ Inflammation of epididymis and testis is associated with
↓ vascular resistance compared with healthy individuals
– Resistive index (RI) < 0.5 (normal RI in testis ≥ 0.5)
○ Signs of infarction in cases with severe epididymoorchitis
– Relatively avascular areas within hyperemic testis or
epididymis suggests focal infarction, which may be
round or wedge shaped
– Reversal of arterial diastolic flow of testis (seen with
obstruction of venous outflow/venous infarction) is
ominous finding associated with testicular infarction
Nuclear Medicine Findings
• Tc-99m: 90% accurate in differentiating torsion from
epididymitis
○ Increased flow within testicular vessels and vas deferens
on flow study
○ Markedly increased perfusion through spermatic cord
vessels (testicular + deferential arteries)
○ Curvilinear increased activity laterally in hemiscrotum on
static images (also centrally if testis is involved)
Imaging Recommendations
• Best imaging tool
○ Color Doppler US; high frequency transducers (9-15
MHz)
• Protocol advice
○ Comparison with contralateral testis is useful when
increase in vascularity is subtle
DIFFERENTIAL DIAGNOSIS
Testicular Torsion
• Absent or diminished color Doppler flow, "twist" of
spermatic cord in inguinal region
• Epididymis may be enlarged with no vascularity on color
Doppler US
Testicular Lymphoma
• Often large in size at time of diagnosis, commonly occurs in
association with disseminated disease
• Heterogeneous echo pattern; often bilateral; involvement
of epididymis and spermatic cord is common; hemorrhage
and necrosis is rare
Testicular Trauma
• History of trauma; acute pain
• Focal hypoechoic avascular area on color Doppler; rupture
of tunica albuginea associated hematocele
PATHOLOGY
General Features
• Etiology
○ Ascending genitourinary tract infection
– In males 14 to 35 years of age, disease is most
frequently caused by Neisseria gonorrhoeae and
Chlamydia trachomatis
– In prepubertal boys, men over 35 years of age, and
men who practice anal intercourse, disease is most
frequently caused by Escherichia coli
Diagnoses: Scrotum
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