DOI:10.2214/AJR.06.1345
AJR 2007; 189:130-135
© American Roentgen Ray Society
CT and MRI of Congenital Anomalies of the Seminal Vesicles
Sandeep S. Arora1,
Richard S. Breiman1,
Emily M. Webb1,
Antonio C. Westphalen1,
Benjamin M. Yeh1 and
Fergus V. Coakley1
1 All authors: Department of Radiology, University of California, San Francisco,
505 Parnassus Ave., Rm. M-372, Box 0628, San Francisco, CA 94143-0628.
Received October 10, 2006;
accepted after revision February 5, 2007.
Address correspondence to F. V. Coakley
(fergus.coakley{at}radiology.ucsf.edu).
Abstract
OBJECTIVE. The purpose of this article is to provide a current
review of the spectrum of CT and MRI findings seen in common congenital
anomalies of the seminal vesicles.
CONCLUSION. CT and MRI can both accurately show renal and seminal
vesicle anomalies. Seminal vesicle anomalies often occur concurrently with
renal and vasal defects. MRI is a better tool for accurately defining anatomic
relationships when one is planning to excise a seminal vesicle cyst or if one
is considering a difficult differential diagnosis.
Keywords: congenital anomalies • CT • genitourinary tract imaging • MRI • reproductive organ imaging • seminal vesicles • urinary tract
Introduction
Congenital anomalies of the seminal vesicles can be categorized into
abnormalities of number (agenesis, fusion, duplication), maturation
(hypoplastic), position (ectopia), and structure (diverticulum, cyst,
communication with the ureter)
[1]. In practice, agenesis and
cystic anomalies are the most commonly encountered abnormalities. Upper
urinary tract anomalies often coexist because of the close embryologic
association of the male reproductive and urinary systems. Although congenital
anomalies of the seminal vesicles are rare, they are likely to be increasingly
encountered because of the continued growth in the use of pelvic CT and MRI.
The diagnosis of seminal vesicle anomalies is often delayed or missed as a
result of both the rarity of these disorders and the wide spectrum of
potentially confusing imaging findings they can produce. This article provides
a current review of the spectrum of CT and MRI findings seen with common
congenital anomalies of the seminal vesicles.
Agenesis of the Seminal Vesicle
Seminal vesicle agenesis does not occur as an isolated phenomenon
(Fig. 1A). It can be seen in
two subsets of patients. In the first subset, an insult of unknown nature or
genetic basis occurs to the mesonephric duct during embryogenesis. There is
generally associated ipsilateral or bilateral agenesis or ectopia of the vas
deferens
[2-5].
If the insult occurs before 7 weeks of gestation (i.e., before ureteral
budding), patients will have associated ipsilateral renal agenesis
[2]
(Fig. 1B).
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Fig. 1A —32-year-old man with symptoms of appendicitis. Axial
contrast-enhanced CT scan through pelvis shows absence of left seminal vesicle
as incidental finding. Normal right seminal vesicle (arrow) is
visible.
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Fig. 1B —32-year-old man with symptoms of appendicitis. Coronal
reformation shows associated ipsilateral agenesis of left kidney. Normal right
kidney is visible. Again note absence of left seminal vesicle, but normal
right seminal vesicle (arrow) is seen.
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In the second subset, bilateral or unilateral seminal vesicle agenesis is
associated with corresponding agenesis of the vas deferens, the kidneys are
normal, and there is an underlying mutation in the cystic fibrosis
transmembrane conductance regulator gene CFTR. These patients are
considered to have a primary genital form of cystic fibrosis
[3,
6]. The agenesis is likely due
to luminal blockade of the vas deferens and seminal vesicles by thick
secretions; it probably occurs after 7 weeks of gestation.
The major symptom associated with these conditions is infertility, although
testicular spermatogenesis is intact. In a small fraction of patients, the
ectopic vas deferens may insert into a müllerian duct remnant, which
becomes dilated. Such cysts may cause symptoms such as hemospermia,
epididymitis, perineal pain, and urinary tract infections.
Congenital agenesis of the seminal vesicle is not surgically correctable
and requires no treatment in the subgroup of unilateral seminal vesicle
agenesis with a patent contralateral ductal system. In symptomatic patients,
surgical options include vasoepididymostomy, transurethral resection of the
ejaculatory duct, and microscopic epididymal, testicular, or vasal sperm
aspiration [4].
Congenital Cystic Anomalies of the Seminal Vesicle
Congenital cysts of the seminal vesicle can be subcategorized as isolated
cysts, cysts associated with upper urinary tract anomalies, and cysts
associated with autosomal dominant polycystic kidney disease. Cysts of the
seminal vesicle usually become apparent during the second to third decade of
life, perhaps related to the onset of sexual activity at this age
[7]. Cysts are mostly smaller
than 5 cm in diameter and are often discovered incidentally, but they may
present with a wide variety of symptoms such as hematuria, hemospermia,
epididymitis, prostatitis, infertility, and urinary tract infections
[7-10].
Giant cysts may present with bowel or bladder obstruction
[8]. Symptomatic cysts can be
excised. Sometimes elective excision is performed when cysts are detected
prenatally or at an early age to prevent future complications.
A seminal vesicle cyst can be seen on CT as a well-defined retrovesicular
mass of water or near-water attenuation that arises from the seminal vesicle
cephalic to the prostate gland
[11]
(Fig. 2A). Reported findings
have been variable, ranging from a cystic pelvic mass with a thick irregular
wall to apparent enlargement of the ipsilateral seminal vesicle
[9]. On MRI, seminal vesicle
cysts are of variable signal intensity on T1-weighted images, are generally of
fluid signal intensity on T2-weighted images, and are nonenhancing after IV
gadolinium administration (Figs.
2B,
2C, and
2D). Increased T1-weighted
intensity is thought to reflect hemorrhage or an increased concentration of
proteinaceous fluid [11].
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Fig. 2A —31-year-old man with hematuria. Axial unenhanced CT scan
shows large seminal vesicle cyst (arrow) to be well-defined
low-attenuation mass posterior to bladder and arising from seminal
vesicle.
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Fig. 2B —31-year-old man with hematuria. Axial T1-weighted MR image
with fat saturation shows left seminal vesicle cyst (arrow) of high
T1 signal intensity, presumably due to proteinaceous or hemorrhagic
content.
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Cysts of the seminal vesicle are associated with ipsilateral renal agenesis
or dysplasia in two thirds of patients, presumably reflecting maldevelopment
of the distal mesonephric duct and faulty ureteral budding (leading to renal
agenesis or dysplasia) and atresia of the ejaculatory duct (leading to
obstruction and cystic dilatation of the seminal vesicle)
[10,
11]. In a sonographic
screening study of the kidneys in 280,000 children in Taipei, the frequency of
presumed seminal vesicle cysts with ipsilateral renal agenesis or dysplasia
was 0.0046% [12]. Bilateral
congenital cysts can be seen in patients with autosomal dominant polycystic
kidney disease (Figs. 3A and
3B).
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Fig. 3A —34-year-old man with known autosomal dominant polycystic
kidney disease, infertility, and recurrent epididymitis. In axial unenhanced
CT scan, bilateral seminal vesicle cysts (arrows) are visible as
multilobular, well-circumscribed, low-attenuation structures.
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Fig. 3B —34-year-old man with known autosomal dominant polycystic
kidney disease, infertility, and recurrent epididymitis. Coronal reformatted
image shows typical appearance of autosomal dominant polycystic kidney disease
involving both kidneys (arrows).
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Cystic dilatation of the seminal vesicle may also occur along with ectopic
ureteral insertion into the seminal vesicle, presumably due to ureteral
budding occurring from the portion of the mesonephric duct destined to be the
seminal vesicle [11] (Figs.
4A,
4B,
5A,
5B,
6A, and
6B). The ipsilateral kidney is
frequently maldeveloped as well. Both CT and MRI can show the urinary tract
anomalies well, but sometimes CT cannot show the opening of the ectopic
ureter. MRI is better for showing the connection between the ectopic ureter
and the seminal vesicles.
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Fig. 4A —Male fetus at 30 weeks of gestation. MRI was performed for
further evaluation of abnormal prenatal sonography. Sagittal T2-weighted
single-shot fast spin-echo MR image (TR/TE, infinite/96) shows two cystic,
fluid-filled masses in fetal pelvis. At postnatal surgery, anterior mass
(white arrow) was found to be bladder, and posterior mass (black
arrow) was dilated distal ureter inserting into dilated seminal
vesicle.
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Fig. 4B —Male fetus at 30 weeks of gestation. MRI was performed for
further evaluation of abnormal prenatal sonography. Coronal T2-weighted MR
image shows ipsilateral multicystic dysplastic kidney (arrow)
adjacent to dilated ureter and seminal vesicle (asterisk).
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Fig. 5A —22-year-old man with chronic pelvic pain. Axial T2-weighted
MR image shows dilatation of right seminal vesicle (arrow). Fluid
level is also present, presumably reflecting proteinaceous content or prior
hemorrhage.
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Fig. 5B —22-year-old man with chronic pelvic pain. Coronal T2-weighted
MRI image shows that cystic dilatation is due to communication with markedly
atrophic and hydronephrotic pelvic right kidney (arrow).
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Fig. 6A —34-year-old man with tongue cancer. Coronal reformatted
contrast-enhanced CT image shows incidental left renal agenesis and dilated
left ureter (arrow) draining into cystic ipsilateral seminal vesicle
(asterisk).
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Differential Diagnosis for Seminal Vesicle Cysts
Congenital cysts and cystic dilatation of the seminal vesicles can be
mimicked by several cysts and fluid-filled structures arising in neighboring
organs. These include true cysts of the prostate gland, ejaculatory duct
cysts, müllerian duct cysts, prostatic utricle cysts, hydronephrotic
pelvic kidneys, bladder diverticula, and ureteroceles. It is important to be
aware of and consider these differential diagnoses when assessing a possible
seminal vesicle cyst. Differentiating features may include position (median,
paramedian, or lateral), content, associations (renal agenesis or anomalies of
the external genitalia), and imaging characteristics. Examples are shown in
Figures 7A,
7B,
7C,
8,
9, and
10.
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Fig. 7A —68-year-old man with hematuria and bladder cancer. Axial
delayed contrast-enhanced CT scan shows fluid-filled structure
(arrow) in right hemipelvis could be mistaken for seminal vesicle
cyst.
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Fig. 7B —68-year-old man with hematuria and bladder cancer.
Maximum-intensity-projection T2-weighted MR urographic image shows that
fluid-filled structure in right pelvis is dilated ureter (arrow).
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Fig. 7C —68-year-old man with hematuria and bladder cancer. Axial
delayed contrast-enhanced CT section at higher level than A shows
horseshoe kidney with markedly dysplastic right-sided moiety (arrow).
Surgery confirmed that fluid-filled structure in right hemipelvis seen in
A was a dilated ureter arising from a dysplastic right-sided moiety of
a horseshoe kidney, and also showed right ureter draining into prostate, with
bilateral absence of seminal vesicles.
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Fig. 8 —Contrast-enhanced axial CT scan in 84-year-old man with
history of prior nephrectomy for renal cell carcinoma. Large fluid-filled
bladder diverticulum (asterisk) arising off bladder posteriorly could
be mistaken for seminal vesicle cyst.
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Fig. 9 —Axial T2-weighted MR image in 72-year-old man with prostate
cancer. Large midline müllerian duct cyst (arrow) is seen
posterior to prostate. Midline location is typical of such cyst and is a
useful feature for differentiating from seminal vesicle cyst.
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Fig. 10 —Endorectal seminal vasography (or vesiculography) in
42-year-old man with infertility. This study is helpful in confirming that
periprostatic structure is due to dilated ejaculatory duct (arrow)
upstream from obstruction of entrance of ejaculatory duct into prostatic
urethra. Injection of contrast material under endorectal sonographic guidance
both opacifies dilated obstructed duct and confirms that it is obstructed,
because contrast material does not pass into prostatic urethra.
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Conclusion
CT and MRI can both accurately show renal and seminal vesicle anomalies.
Seminal vesicle anomalies often occur concurrently with defects of the kidney
and vas deferens. MRI is a better tool for accurately defining anatomic
relationships when one is planning to excise a seminal vesicle cyst or if one
is considering a difficult differential diagnosis because of its multiplanar
imaging capability, superior soft-tissue contrast, and lack of ionizing
radiation. MRI may also help depict the opening of the associated ectopic
ureter. Seminal vesicle agenesis is always associated with anomalies of the
vas deferens. Ectopia of vas deferens can be confirmed only by invasive
vasography [4]. Diagnostic
imaging is usually not necessary for determining the absence of a vas deferens
because a clinician can make the diagnosis by palpation, although absence can
be confirmed by thinslice CT or MRI.
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Abstract
Introduction
