DOI:10.2214/AJR.06.0759
AJR 2007; 188:1373-1379
© American Roentgen Ray Society
Endorectal MRI of Prostatic and Periprostatic Cystic Lesions and Their Mimics
Sean Curran1,
Oguz Akin1,
A. Muhtesem Agildere2,
Jingbo Zhang1,
Hedvig Hricak1 and
Jürgen Rademaker1
1 Department of Radiology, Memorial Sloan-Kettering Cancer Center, 1275 York
Ave., New York, NY 10021.
2 Department of Radiology, Baskent University School of Medicine, Ankara,
Turkey.
Received June 16, 2006;
accepted after revision November 21, 2006.
Address correspondence to O. Akin
(akino{at}mskcc.org).
CME
This article is available for CME credit. See
www.arrs.org
for more information.
FOR YOUR INFORMATION
This article is available for CME credit. See
www.arrs.org
for more information.
Keywords: genitourinary tract imaging • MRI • pelvic imaging • prostate gland
Introduction
Endorectal MRI of the prostate is a promising technique for the
assessment of prostate cancer; it provides noninvasive depiction of the
prostate gland with excellent anatomic detail. Although prostatic and
periprostatic cystic lesions are uncommon entities, they are sometimes
encountered on endorectal MRI, which is increasingly used for the pretreatment
evaluation of prostate cancer and male infertility. This article describes the
MRI appearances of cystic lesions of the prostate and adjacent structures and
briefly reviews their clinical significance.
Anatomy
The prostate gland is composed of peripheral, central, and transition zones
and a fibromuscular stroma (Fig.
1). The fibromuscular stroma is located anteriorly. The peripheral
zone envelops the posterior, lateral, and apical portions of the prostate. The
central zone is located posteriorly and superiorly between the peripheral zone
and the proximal urethra. The transition zone is located anteriorly and
laterally to the proximal urethra. The seminal vesicles and vasa deferentia
are located just above the base of the prostate and behind the urinary
bladder. The ducts of the seminal vesicles join the vasa deferentia to form
the ejaculatory ducts, which open into the urethra at the level of the
verumontanum. Knowledge of the embryology of the wolffian and müllerian
duct systems in the male is important to understand normal anatomy and
prostatic cyst location and their development. The wolffian duct gives rise
not only to the vas deferens, the seminal vesicle, the ejaculatory duct, the
epididymis, and the appendix of epididymis, but also to the renal collecting
system and the ureter. The müllerian duct contributes to the appendix
testis and the prostatic utricle. The urinary bladder, the prostate gland, and
the prostate utricle arise from the urogenital sinus.
Cysts in the region of the prostate seen on MRI may be described as either
intraprostatic or periprostatic. Appendix
1 summarizes the most commonly seen cystic lesions of the prostate
and adjacent structures and their mimics.
APPENDIX 1 : Most Commonly Seen Prostatic and Periprostatic Cystic Lesions and
Their Mimics
| A. Intraprostatic Cystic Lesions |
| 1. Müllerian duct cysts and prostatic utricle cysts |
| 2. Ejaculatory duct cysts |
| 3. Prostatic retention cysts |
| 4. Cystic degeneration of benign prostatic hypertrophy |
| 5. Cysts associated with tumors |
| 6. Infectious, inflammatory, and parasitic cysts |
| 7. Ejaculatory duct diverticulum |
| B. Periprostatic Cystic Lesions |
| 1. Seminal vesicle cysts |
| 2. Cysts of the vas deferens |
| 3. Cowper's duct cysts |
| C. Entities That May Mimic Prostatic and Periprostatic Cystic Lesions |
| 1. Defect from transurethral resection of the prostate |
| 2. Hydroureter and ectopic insertion of the ureter |
| 3. Bladder diverticulum |
| 4. Prominent seminal vesicles |
|
Intraprostatic Cystic Lesions
Müllerian Duct Cysts and Prostatic Utricle Cysts
Although these conditions are believed to be two different entities, it is
difficult to differentiate them from one another on imaging and clinical
studies
[1-3].
Both occur in the midline. Müllerian duct cysts originate from the
remnants of the müllerian duct. Prostatic utricle cysts result from the
dilatation of the prostatic utricle.
Müllerian duct cysts may originate from the region of the verumontanum
but usually extend above the prostate and may be slightly lateral to the
midline. They do not communicate with the urethra. Prostatic utricle cysts
always arise from the verumontanum and are always in the midline, and they
communicate with the urethra (Figs.
2A,
2B,
2C and
3).
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Fig. 2A —51-year-old man with prostate cancer. Transverse (A), coronal
(B), and sagittal (C) T2-weighted MR images show prostatic
utricle cyst (UC) that is located in midline, arising from verumontanum and
communicating with urethra (U in C). Transverse image (A) shows
focal low-signal-intensity area representing tumor (T in A).
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Fig. 2B —51-year-old man with prostate cancer. Transverse (A), coronal
(B), and sagittal (C) T2-weighted MR images show prostatic
utricle cyst (UC) that is located in midline, arising from verumontanum and
communicating with urethra (U in C). Transverse image (A) shows
focal low-signal-intensity area representing tumor (T in A).
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Fig. 2C —51-year-old man with prostate cancer. Transverse (A), coronal
(B), and sagittal (C) T2-weighted MR images show prostatic
utricle cyst (UC) that is located in midline, arising from verumontanum and
communicating with urethra (U in C). Transverse image (A) shows
focal low-signal-intensity area representing tumor (T in A).
|
|
Müllerian duct cysts and prostatic utricle cysts may cause obstructive
urinary symptoms, hematuria, and pelvic pain. They may also cause ejaculatory
impairment by obstruction of the ejaculatory ducts in the midline. Because
utricle cysts communicate with the urethra, they may result in postvoid
dribbling. Prostatic utricle cysts are associated with some genitourinary
abnormalities such as hypospadias, incomplete testicular descent, and
unilateral renal agenesis. On aspiration, müllerian duct cysts (Fig.
4A,
4B) never contain spermatozoa;
whereas utricle duct cysts occasionally do. Both müllerian duct cysts and
prostatic utricle cysts can become infected and may contain pus or hemorrhage,
which can cause confusion on imaging because the appearances overlap those of
abscess and cystic tumor of the prostate. Müllerian duct cysts commonly
contain calculi. There have been case reports of müllerian duct cysts and
prostatic utricle cysts containing carcinoma
[4,
5]. Not all cystic lesions
located at the midline of the prostate are müllerian duct cysts or
prostatic utricle cysts, and the possibility of other cystic lesions should
also be considered [6].
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Fig. 4A —65-year-old man with prostate cancer. Transverse (A) and
sagittal (B) T2-weighted MR images show müllerian duct cyst (M)
that is slightly lateral to midline and extends above prostate.
|
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Fig. 4B —65-year-old man with prostate cancer. Transverse (A) and
sagittal (B) T2-weighted MR images show müllerian duct cyst (M)
that is slightly lateral to midline and extends above prostate.
|
|
Ejaculatory Duct Cysts
Ejaculatory duct cysts are rare. They are due to obstruction of the
ejaculatory duct that may be congenital or acquired
[7]. On imaging, these lesions
appear to be cystic structures along the ejaculatory duct just lateral to the
midline in the central zone of the prostate. However, when they are large,
they may extend cephalad to the prostate and appear to arise centrally (Fig.
5A,
5B).
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Fig. 5A —35-year-old man with azoospermia. Coronal (A) and transverse
(B) T2-weighted MR images show ejaculatory duct cyst (EDC) that extends
from verumontanum to left of midline above prostate (P in A) along
course of ejaculatory duct. Hemorrhage (arrow, B) layering at
dependent aspect of cyst is also seen.
|
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Fig. 5B —35-year-old man with azoospermia. Coronal (A) and transverse
(B) T2-weighted MR images show ejaculatory duct cyst (EDC) that extends
from verumontanum to left of midline above prostate (P in A) along
course of ejaculatory duct. Hemorrhage (arrow, B) layering at
dependent aspect of cyst is also seen.
|
|
On aspiration they contain fructose or spermatozoa. Ejaculatory duct cysts
commonly contain calculi. Sometimes they may contain pus or hemorrhage. There
may be associated cystic dilatation of the seminal vesicle on the same side.
Patients often present with hematospermia or dysuria. Diverticula of the
ejaculatory duct are probably even more rare than cysts of the ejaculatory
duct.
Prostatic Retention Cysts
Retention cysts are acquired cysts that result from obstruction of the
glandular ductules, causing dilatation of the acini. They may occur in any
glandular zone of the prostate. They never contain spermatozoa on aspiration.
Retention cysts usually appear as smooth-walled, unilocular simple cysts
[1] (Fig.
6A,
6B). They rarely cause
symptoms.
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Fig. 6A —66-year-old man with prostate cancer. Transverse (A) and
coronal (B) T2-weighted MR images show unilocular, smooth, and
thin-walled prostatic retention cyst (RC) in peripheral zone (PZ in B)
of prostate.
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Fig. 6B —66-year-old man with prostate cancer. Transverse (A) and
coronal (B) T2-weighted MR images show unilocular, smooth, and
thin-walled prostatic retention cyst (RC) in peripheral zone (PZ in B)
of prostate.
|
|
Cystic Degeneration of Benign Prostatic Hypertrophy (BPH)
Cystic degeneration of BPH nodules is common and accounts for most
prostatic cystic lesions. Cystic lesions resulting from cystic degeneration of
BPH are located in the transition zone of the prostate along with BPH nodules
(Fig. 7A,
7B). They may be seen in
irregular shapes and various sizes and may contain hemorrhage or calculi.
Patients with these cysts usually have urinary obstructive symptoms due to
BPH.
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Fig. 7A —59-year-old man with prostate cancer. Sagittal (A) and
transverse (B) T2-weighted images show hypertrophic transition zone
(TZ) indenting urinary bladder (B in A). Note that one of benign
prostatic hyperplasia nodules (N) has a cystic component
(arrows).
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Fig. 7B —59-year-old man with prostate cancer. Sagittal (A) and
transverse (B) T2-weighted images show hypertrophic transition zone
(TZ) indenting urinary bladder (B in A). Note that one of benign
prostatic hyperplasia nodules (N) has a cystic component
(arrows).
|
|
Cysts Associated with Tumors
Both benign and malignant prostate neoplasms may contain cystic components.
Multilocular prostatic cystadenoma is a rare benign tumor that can grow to a
large size [8]. Prostatic
adenocarcinoma may show cystic features from time to time. Other tumors of the
prostate gland that exhibit cystic components include papillary
cystadenocarcinoma and combined transitional cell/adenocarcinoma. Rarely,
leiomyoma or liposarcoma in the prostate may have cystic elements. On MRI, the
heterogeneity of signal intensity of the cystic components and the presence of
soft-tissue elements in the lesion indicate a neoplastic cause (Fig.
8A,
8B).
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Fig. 8A —68-year-old man with mixed tumor of prostate containing high-grade
ductal adenocarcinoma, with transitional cell and nonkeratinizing squamous
cell differentiation. Transverse (A) and coronal (B) T2-weighted
MR images show tumor (T) with cystic and solid components. Fluid-fluid level
(arrow, A) is also seen at dependent portion of cystic
component of tumor.
|
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Fig. 8B —68-year-old man with mixed tumor of prostate containing high-grade
ductal adenocarcinoma, with transitional cell and nonkeratinizing squamous
cell differentiation. Transverse (A) and coronal (B) T2-weighted
MR images show tumor (T) with cystic and solid components. Fluid-fluid level
(arrow, A) is also seen at dependent portion of cystic
component of tumor.
|
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Infectious, Inflammatory, and Parasitic Cysts
A prostatic abscess may form secondary to acute bacterial infection, most
often with Escherichia coli. Older diabetic patients are at increased
risk. Patients usually have typical clinical signs and symptoms including
fever, chills, dysuria, urinary frequency and urgency, hematuria, and pain.
Although MRI is usually not performed for this condition, suspicion of an
abscess is raised when a cystic lesion with thickened walls, septations, or
heterogeneous contents is seen in a patient with appropriate clinical findings
[9].
Chronic prostatitis may lead to a condition called cavitary prostatitis, in
which a combination of prolonged infections and fibrosis causes glandular
ductal constriction and acinar dilatation. This results in a "Swiss
cheese" appearance in the prostate, with multiple small cysts of various
sizes scattered throughout the gland (Fig.
9A,
9B). Correlation with clinical
history is useful in these cases.
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Fig. 9A —68-year-old man with prostate cancer and chronic prostatitis.
T2-weighted coronal MR image (A) shows multiple peripheral cystic areas
(arrows, A) consistent with pathologically proven chronic
prostatitis (arrows, B), as shown on step-section pathology
image (B).
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Fig. 9B —68-year-old man with prostate cancer and chronic prostatitis.
T2-weighted coronal MR image (A) shows multiple peripheral cystic areas
(arrows, A) consistent with pathologically proven chronic
prostatitis (arrows, B), as shown on step-section pathology
image (B).
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Parasitic (echinococcal and bilharzial) cysts in the prostate are rare and
occur in the geographic regions where these parasites are endemic.
Periprostatic Cystic Lesions
Seminal Vesicle Cysts
Cysts in the seminal vesicles are often discovered incidentally. However,
if very large, they may be associated with voiding difficulties. They are
commonly associated with adult polycystic kidney disease
[10,
11]. Aspiration of seminal
vesicle cysts yields spermatozoa and sometimes hemorrhage. Figure
10A,
10B,
10C provides an example of a
seminal vesicle cyst depicted on MRI.
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Fig. 10A —35-year-old man with seminal vesicle cyst. Transverse (A) and
sagittal (B) T2-weighted MR images show right seminal vesicle cyst
(SVC) above prostate (P in B). Note that left seminal vesicle
(arrow, A and C) is normal (A and C).
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Fig. 10B —35-year-old man with seminal vesicle cyst. Transverse (A) and
sagittal (B) T2-weighted MR images show right seminal vesicle cyst
(SVC) above prostate (P in B). Note that left seminal vesicle
(arrow, A and C) is normal (A and C).
|
|
Cysts of the Vas Deferens
These cysts are located superior to the prostate gland along the course of
the vas deferens. On MRI, vas deferens cysts are easily recognized and
distinguished from other adjacent structures.
Cowper's Duct Cysts
The Cowper's (bulbourethral) glands are found in the urogenital diaphragm
immediately inferior to the prostate. The Cowper's gland ducts drain into the
bulbous urethra, and obstruction of these ducts may cause retention cysts.
Cowper's duct cysts (Fig. 11A,
11B) may be congenital or
acquired, usually due to trauma or infection. Larger cysts may present with
hematuria or urinary obstruction and, potentially, male infertility
[12].
Mimics of Prostatic and Periprostatic Cystic Lesions
Defect from Transurethral Resection of the Prostate
A defect from the transurethral resection of the prostate gland is located
centrally. The superior portion of this defect communicates with the bladder
and appears on MRI as an irregular funnel-shaped defect (Fig.
12A,
12B,
12C).
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Fig. 12A —76-year-old man with previous transurethral resection of prostate
gland and newly diagnosed prostate cancer. Transverse (A) and coronal
(B) T2-weighted MR images show cystic space (arrows) in center
of prostate (P).
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Fig. 12B —76-year-old man with previous transurethral resection of prostate
gland and newly diagnosed prostate cancer. Transverse (A) and coronal
(B) T2-weighted MR images show cystic space (arrows) in center
of prostate (P).
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Fig. 12C —76-year-old man with previous transurethral resection of prostate
gland and newly diagnosed prostate cancer. Sagittal T2-weighted MR image shows
funnel-shaped defect (arrows) that communicates with urinary bladder
(B). P = prostate.
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Hydroureter and Ectopic Insertion of Ureter
The tortuous course of a hydroureter can mimic a periprostatic cystic
lesion. In addition, ectopic insertion of a ureter into the prostatic urethra
can resemble a tubular cystic structure when dilated. Careful review of MR
images in multiple planes helps identify the true nature of these conditions
(Fig. 13A,
13B).
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Fig. 13A —71-year-old man with prostate cancer. Sagittal T2-weighted MR images
incidentally show tortuous hydroureter (H) with ectopic insertion into base of
prostate (P in A) below urinary bladder (B).
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Fig. 13B —71-year-old man with prostate cancer. Sagittal T2-weighted MR images
incidentally show tortuous hydroureter (H) with ectopic insertion into base of
prostate (P in A) below urinary bladder (B).
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Bladder Diverticulum
Bladder diverticula occur commonly. They may lie alongside the prostate or
seminal vesicles when they extend posteriorly and may be confused with cysts
of these structures. However, visualization of their communication with the
urinary bladder helps clarify their true origin
(Fig. 14).
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Fig. 14 —61-year-old man. Transverse T2-weighted MR image shows right
posterolateral urinary bladder diverticulum (D) that extends above prostate.
Note urine flow through neck of diverticulum (arrow).
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Prominent Seminal Vesicles
The appearance and size of the seminal vesicles vary considerably.
Sometimes they are prominent and can mimic periprostatic cysts. However, the
typical convoluted appearance of the seminal vesicles and their communication
with the ejaculatory ducts assist in making the correct diagnosis (Fig.
15A,
15B).
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Fig. 15A —57-year-old man with prostate cancer. Coronal T2-weighted MR images
show prominent seminal vesicles (SV) bilaterally that may mimic a
periprostatic cystic lesion. Note typical convoluted appearance of seminal
vesicles and their communication with ejaculatory ducts (ED in B).
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Fig. 15B —57-year-old man with prostate cancer. Coronal T2-weighted MR images
show prominent seminal vesicles (SV) bilaterally that may mimic a
periprostatic cystic lesion. Note typical convoluted appearance of seminal
vesicles and their communication with ejaculatory ducts (ED in B).
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Summary
The differential diagnosis of the various types of prostatic or
periprostatic cystic lesions can be difficult, and it is complicated by the
fact that cystic lesions originating from adjacent structures can mimic
prostatic or periprostatic cystic lesions. Exact anatomic localization using
MRI and appropriate clinical history are useful in narrowing the differential
diagnosis and deciding whether to pursue further invasive diagnostic
tests.
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Introduction
Anatomy
