AJR 2005; 184:1594-1596
© American Roentgen Ray Society
CT Voiding Cystourethrography Using 16-MDCT for the Evaluation of Female Urethral Diverticula: Initial Experience
Sun Ho Kim1,
Seung Hyup Kim1,
Byung Kwan Park1,
Se Young Jung1,
Sung Il Hwang1,
Jae-Seung Paick2 and
Soo Woong Kim2
1 Department of Radiology, Seoul National University College of Medicine, Seoul,
Korea.
2 Department of Urology, Seoul National University College of Medicine, Seoul,
Korea.
Received June 8, 2004;
accepted after revision September 9, 2004.
Address correspondence to Seung Hyup Kim, Seoul National University
Hospital, 28 Yongon-Dong, Chongno-Gu, Seoul 110-744, Korea
(kimsh{at}radcom.snu.ac.kr).
Introduction
Conventional voiding cystourethrography (VCUG), transvaginal sonography
(TVUS), and MRI have been used for the evaluation of urethral diverticula
[1–7].
These imaging techniques, however, rarely identify the exact location of the
ostium of a diverticulum in the urethra, which is the most important
information for urologists who plan surgery
[8,
9]. We report our initial
experiences with CT VCUG using 16-MDCT for the evaluation of female urethral
diverticula. With this technique, the accurate locations of the ostia of
diverticula were clearly shown, which was not possible with conventional VCUG,
TVUS, or MRI. CT VCUG is a useful imaging technique for the evaluation of
urethral diverticula and may replace conventional VCUG, TVUS, or MRI for this
purpose.
Materials and Methods
Patient Selection
Over a 3-month period, two women (39 and 52 years old) with known urethral
diverticula were scheduled for surgery. In both patients, conventional VCUG
and TVUS were performed before CT VCUG. In the 39-year-old woman, MRI was also
performed. These studies showed the presence of diverticula but did not
identify the exact locations of the openings in the urethra (ostia of
diverticula) (Figs. 1A and
2A).
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Fig. 1A. —Urethral diverticulum in 52-year-old woman. Conventional
voiding cystourethrography (VCUG) image shows urethral diverticulum, lumen of
which is partially filled with contrast medium (arrows).
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Fig. 2A. —Urethral diverticulum in 39-year-old woman. Left paramedian
T2-weighted sagittal MR image (TR/TE, 4.3/2.2; flip angle, 37°) obtained
using 3D true fast imaging with steady-state free precession sequence while
patient voids shows part of urethral diverticulum (arrows) anterior
to proximal urethra (U). Reformatted coronal image (asterisk) also
shows part of diverticulum left lateral to proximal urethra. Ostium or neck is
not visible on this image and could not be identified on other MR images (not
shown).
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CT Technique
Before CT VCUG, conventional VCUG was performed for the comparison and to
fill the lumen of diverticula sufficiently with contrast medium (60 mL of
Telebrix 30 [ioxithalamate], Guerbet) diluted in 440 mL of normal saline. The
bladder was then refilled with as much as 300 mL of the same contrast medium.
The patient was transferred to the CT room and was in a supine position on the
CT table. A 16-MDCT scanner (Sensation 16, Siemens) was used, with a detector
configuration of 0.75 mm x 16 and a pitch of 1.25. The gantry was
positioned at the level from which the scanning would start, usually at the
top of the bladder, and was ready to scan. The patient was asked to void and
told to raise her arm when she voided. As soon as this signal was noticed, an
unenhanced scan was obtained down to the inferior margin of symphysis pubis.
The actual scanning time was less than 7 sec. Axial images were reconstructed
with a 1-mm thickness and interval, and thin-slab (2-mm) coronal and sagittal
images and 3D images were reformatted.
Results
In both patients, the diverticula and the ostia were clearly shown. In one
patient, the diverticulum was located left lateral to the proximal urethra,
and the ostium was identified at the 5-o'clock position (left posterolateral)
from the urethral lumen and the neck coursed up to the diverticulum (Fig.
1A,
1B,
1C). In the other patient, the
diverticulum was in an anterolateral position to the proximal urethra, and the
ostium was also found at the 5-o'clock position (Fig.
2A,
2B,
2C). The ostia could be seen in
all imaging planes (axial, sagittal, and coronal) and in 3D images. Among
these, axial images were most helpful in identifying the ostia. However, the
course of the neck and the relationship with the urethra were shown most
clearly in 3D or coronal images. These CT VCUG findings were well correlated
with the findings during surgery.
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Fig. 1B. —Urethral diverticulum in 52-year-old woman. Three-dimensional
reformatted CT VCUG image (left anterior view) shows diverticulum (large
arrows) left lateral to proximal urethra (U), and ostium (small
arrow) is identified.
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Fig. 2B. —Urethral diverticulum in 39-year-old woman. Three-dimensional
reformatted CT voiding cysto-urethrography (VCUG) image (left posterior view)
shows ostium (arrowhead) of diverticulum (arrows)
surrounding proximal urethra (U) anterolaterally. Proximal urethra is
abnormally dilated because of previous surgery.
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Discussion
The prevalence of female urethral diverticulum has been reported as
0.6–6% [1]. Symptoms are
mostly nonspecific. Differential diagnosis includes paraurethral cyst,
periurethral abscess, or cysts of vagina (e.g., Gartner's duct cysts). Common
complications are infection and stone formation; malignancies can also arise
[1,
2].
Identification of the ostium of a diverticulum is important for successful
surgical management. Urethroscopy is usually performed for this purpose but
sometimes fails. The identification of the ostium on urethroscopy is
especially difficult when infection or obstruction is present in the neck of a
diverticulum. Thus, radiologic information about the location of ostia is
useful for urologists who are planning surgery
[8,
9].
Conventional VCUG alone is not sufficient for the detection of diverticula.
Double-balloon urethrography had been introduced to improve the sensitivity,
but it is not practical in many patients because of its invasiveness
[3,
10]. TVUS is favored for its
minimal invasiveness, but has a limited role because of its poor specificity
in the differentiation from other periurethral lesions
[4,
5]. MRI is superior to other
techniques in its sensitivity and in showing the relationship of diverticulum
with urethra in multiplanes with good soft-tissue contrast, but did not
succeed in showing the exact location of the ostia in previous reports
[1,
2,
6,
7]. Although a relatively long
scanning time may be overcome by fast 3D MR sequences and the resolution can
be increased by endorectal coil
[6,
7], the quality of MR images
scanned during voiding is not good enough to show the ostia or neck of a
diverticulum as we show in Figure
2A. The high cost of MRI is another limitation.
Conventional CT can also show diverticula but generally has not been used
for this purpose. Advantages of MDCT include rapid scanning, thin collimation,
and highly improved resolution of the z-axis, resulting in
multiplanar and 3D reformatted images of high quality, making it possible to
obtain images close to those of conventional VCUG. Furthermore, it is also
possible to show the exact location of the opening of diverticulum in the
urethra and to clearly and directly visualize the neck, which has been very
difficult or almost impossible with other imaging techniques.
Although our initial experience of CT VCUG revealed its usefulness in the
evaluation of diverticula, some practical problems should be solved before
this imaging technique gains popularity. The procedure is time consuming.
Second, difficulty for some patients in self-voiding while lying on CT table
may lengthen the examination time or make it impossible to obtain voiding
images. However, this limitation is also true of conventional VCUG. Finally,
the problem of radiation should be considered, because many patients are of
reproductive age and the pelvis and genitalia are within the scan regions. We
think the radiation exposure by CT VCUG is within a tolerable and acceptable
range when considering its usefulness. We did not actually measure the amount
of radiation, and caution is necessary, especially in young patients.
With these satisfactory initial results, we will evaluate more patients
with urethral diverticula using CT VCUG, and the results will be presented in
future reports. A more simplified and tolerable procedure is also being
planned. Possible application of CT VCUG in diseases other than urethral
diverticula is being considered.
In conclusion, although preliminary and performed in a small number of
patients, our successful results suggest that CT VCUG with 16-MDCT may become
an outstanding imaging technique for the evaluation of urethral diverticula,
especially to clearly and accurately show the opening in the urethra and the
neck of the diverticulum.
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Introduction
Materials and Methods
