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Imaging for Male Infertility
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- After male infertility has been diagnosed, ultrasound is the imaging modality of choice for
evaluation of male genital anatomy for possible causes
- Scrotal ultrasound evaluates the testicules, epididymii, and proximal vas deferens, including
abnormalities secondary to distal genital duct obstruction
- Prostate ultrasound evaluates the distal vas deferens, vasal ampullae, seminal vesicles, the
prostate gland, and ejaculatory ducts for congenital absence, obstruction, and cysts
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Infertility
in a couple is defined as the failure to conceive after 12 months of
frequent unprotected intercourse. In approximately 50% of infertile
couples, the problem is at least in part due to male infertility, which
is initially recognized through semen analysis. If the man is
sub-fertile, he is typically referred to a urologist for evaluation of
possible causes of infertility. Patient history, clinical examination,
and laboratory testing are all essential for evaluation.
Ultrasound is the imaging modality of choice because it can
adequately demonstrate all the essential parts of the male reproductive
system. Although vasography is still regarded as the gold standard for
visualizing the male reproductive tract, it is invasive and carries
with it a risk of damage to the vas deferens and is, therefore, rarely
used. MRI rarely provides information that cannot be obtained by
ultrasound.
Both scrotal and prostate ultrasound
examinations can be done at the same time but because the prostate
examination is a more invasive (transrectal probe), referring
physicians may prefer to schedule a scrotal ultrasound alone. These
imaging examinations are performed to evaluate for disorders that
obstruct sperm transport or to evaluate for congenital absence of the
vas deferens. Together, these disorders account for 10-20% of male
infertility cases. In a small proportion of these cases, imaging
identifies a potentially correctable cause of obstruction. More
commonly, it serves to guide the selection of the best method for
impregnating the female partner, such as sperm aspiration from the
epididymis or seminiferous tubules followed by in vitro fertilization
or intracytoplasmic sperm injection.
| Table 1. Scrotal ultrasound findings in infertile men |
Testicular abnormalities
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Absence
Atrophy
Cryptorchidism
Ectopic location
Abnormalities associated with obstruction, e.g.
mediastinal cysts, enlarged volume |
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Epididymal abnormalities associated with obstruction,
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Epidydimal hypoplasia, abrupt tapering shape
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| Varicoceles |
Scrotal Ultrasound
Scrotal ultrasound can be helpful in determining whether azoospermia is
non-obstructive or obstructive (Table 1) because it can directly detect
abnormalities in the mediastinum testis, epididymis, and the proximal
vas deferens. It can also show secondary changes due to obstructive
abnormalities in the distal genital duct. Epididymal abnormalities
associated with obstruction include tubular ectasia, enlarged
hypoechoic foci (suggestive of inflammatory masses), and abrupt
tapering from the head to body or mid- to distal portions of the
epididymis. Cysts may also be identified within the mediastinum testis.
Appearance of one or more of these abnormalities is indicative of
distal obstruction, with at least one report documenting a sensitivity
of 82%, specificity of 100%, and accuracy of 88%.
Scrotal ultrasound is also used to examine the testes in at least two
planes, the transverse and longitudinal; the size is measured and the
echotexture compared to the other side. Testicular volume is
significantly higher (p < .05) in those with obstructive azoospermia
(median 11.6 cm3, range 7.7 - 25.8 cm3) compared to non-obstructive azoospermia (median 8.3 cm3, range 1.2 – 16.4 cm3).
Also, if a testis is non-palpable, scrotal imaging can determine
whether it is congenitally absent, cryptorchid, atrophic, or ectopic.
Perhaps most commonly, scrotal ultrasound has been used to confirm the
presence of varicocele detected by physical examination or to find
non-palpable varicoceles. It is well known that varicoceles are more
common in infertile men compared to the general population. However,
their significance as a cause of infertility is controversial.
Scrotal ultrasound is recommended before epididymal sperm aspiration
because approximately one third of patients with vasal agenesis have
hypoplasia of the distal two-thirds of the epididymis. Imaging can
identify which portion of the epididymis is longest and most suitable
for aspiration.
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Figure 2.
Transrectal ultrasound of the prostate. Transverse image of the
prostate in a young male demonstrates a small midline cystic structure
(arrow), thought to represent a utricle cyst. In addition to detecting
cystic lesions, trans-rectal ultrasound of the prostate is also used to
evaluate the seminal vesicles and the vas deferens for congenital
abnormalites.
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Figure 1.
Ultrasound of the scrotum. Sagittal image of the left testicle
demonstrates ectasia of the rete testes (solid arrow) with
intratesticular cysts (dashed arrow). This finding, in association with
azoospermia, is suggestive of an obstructive etiology and is helpful in
directing further work-up in the setting of infertility.
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Prostate (Transrectal) Ultrasound
The prostate ultrasound examination is used to examine the distal vas
deferens, vasal ampullae, seminal vesicles, prostate, and ejaculatory
ducts. Anomalies of the vas deferens can range from complete congenital
bilateral or unilateral absence of the vas deferens to vestigial
remnants that appear as isoechoic or hyperechoic oval structures, less
than 3 mm in diameter and located posterior to the bladder. Vasal
agenesis is commonly associated with anomalies of the seminal vesicles
and ejaculatory duct. Overall, vasal agenesis has been reported to
occur in 1.0 – 2.5% of all infertile men but has been reported to
account for 34% of men with low volume azoospermia (Table 2). Vasal
agenesis is also associated with renal anomalies such as ipsilateral
renal agenesis, crossed fused ectopia, or ectopic pelvic kidney. In
addition, up to 82% of men with bilateral vasal agenesis have at least
one detectable gene mutation for cystic fibrosis.
Ductal obstruction is indicated by abnormal echogenicity of the vas
deferens, seminal vesicles, and/or ejaculatory duct. In some cases, the
abnormalities can be subtle and diffuse while in others calcification
is readily apparent. Calculi may develop in an otherwise normal duct or
may develop secondary to obstruction with concretion of static cellular
fluid and debris.
Obstructing cysts are most commonly seen in a periurethral location but
can affect the seminal vesicles or the vas deferens. Midline
periurethral cysts, also known as utricle cysts, are thought to be
derived from an incompletely regressed mullerian duct. Ejaculatory duct
cysts, derived from Woolffian ducts, typically contain sperm and can be
confused with utricle cysts when they appear midline by ultrasound.
Prostatic cysts, also known as retention or degenerative cysts, are
more lateral in location and rarely reach sufficient size to compress
the adjacent ejaculatory ducts and cause infertility. Seminal vesicle
cysts, although rare, are associated with renal disorders and
anomalies, including adult polycystic kidney disease, ipsilateral renal
dysgenesis, duplication of the renal collecting system, ectopic
insertion of the ureter, and ectopic location of the kidney.
| Table 2. Prostate ultrasound findings in infertile men with low-volume azoosperma |
| None |
25% |
| Congenital bilateral absence of the vas deferens |
34% |
Bilateral occlusion of ductal system by fibrosis
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16% |
| Congenital unilateral absence of the vas deferens |
11% |
| Obstructing cysts of the ductal system or prostate |
9% |
| Ductal obstruction due to calculi |
4% |
Radiologic and Surgical Interventions
In some cases, fertility can be restored to patients with cysts that
are occluding part of the ductal system by decompression, provided that
the ductal system itself is intact. In these cases, ultrasound guided
aspiration of the cystic contents is used to relieve the pressure,
which can allow the ducts to open and to function normally. In cases of
distal ductal anomalies, it is sometimes possible to restore fertility
surgically. Alternatively, microscopic sperm aspiration followed by in vitro fertilization or intra-cytoplasmic injection may be successful in producing viable embryos for implantation.
Scheduling
Scrotal and prostate ultrasound may be ordered through ROE at the MGH
Main Campus, Mass General West Imaging Waltham, and MGH Chelsea Health
Center, or by telephone 617-724-XRAY (9729) for all locations.
Further Information
For further questions, please contact Joshua Stuhlfaut, M.D.
, Abdominal Imaging and Intervention, MGH Department of Radiology
We would like to thank Dr. Stuhlfaut and Pablo Gomery, M.D., Department
of Urology, for their assistance and advice for this issue.
This article provided useful information about the appropriate use of imaging studies:
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References
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Beddy, P, Geoghegan, T, Browne, RF and Torreggiani, WC. (2005) Testicular varicoceles. Clin Radiol. 60: 1248-55
Brugh, VM, 3rd and Lipshultz, LI. (2004) Male factor infertility: evaluation and management. Med Clin North Am. 88: 367-85
Kuligowska, E and Fenlon, HM. (1998) Transrectal US in male infertility: spectrum of findings and role in patient care. Radiology. 207: 173-81
Moon, MH, Kim, SH, Cho, JY, Seo, JT and Chun, YK. (2006) Scrotal US for evaluation of infertile men with azoospermia. Radiology. Published online before print, February 7, 2006
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