DOI:10.2214/AJR.04.1457
AJR 2006; 186:136-140
© American Roentgen Ray Society
Opacification of the Collecting System and Ureters on Excretory-Phase CT Using Oral Water as Contrast Medium
Satomi Kawamoto1,
Karen M. Horton1 and
Elliot K. Fishman1
1 All authors: The Russell H. Morgan Department of Radiology and Radiological
Science, Johns Hopkins Hospital, 601 N. Caroline St./3235A, Baltimore, MD
21287.
Received September 14, 2004;
accepted after revision February 16, 2005.
Address correspondence to S. Kawamoto
(skawamo1{at}jhmi.edu).
Keywords: excretory phase • MDCT • opacification • water ingestion
Introduction
CT is widely used as a primary imaging technique for evaluation of urinary
tract abnormalities. Recently, there has been increasing interest in using CT
for the evaluation of the renal collecting system and ureters because of
technical advances including MDCT and 3D software development. Detailed
evaluation of the renal collecting system and ureters is possible with
increased spatial resolution and isotropic data sets that can now be created
using MDCT.
For evaluation of the renal collecting system and ureters, optimal
opacification and distention is essential. Various techniques to optimize
opacification and distention of the renal collecting system and ureters have
been reported in the literature. To optimize opacification, abdominal
compression
[1-5],
saline infusion [6,
7], multiple acquisitions
[2], prone positioning
[1,
6,
7], and furosemide
administration [7] have been
successfully used. Abdominal compression has also been used to improve
distention of the renal collecting system
[4].
As a part of a routine 3-phase CT examination in patients with suspected
urinary tract abnormalities, we evaluated the degree of opacification of the
renal collecting system and ureters on excretory-phase images obtained without
abdominal compression, prone positioning, or IV administration of saline or
furosemide. Instead, 750-1,000 mL of water was ingested as oral contrast and
for diuresis. The purpose of this study is to evaluate the degree of
opacification of the renal collecting system and ureters on excretory-phase
contrast-enhanced CT using only oral ingestion of water without abdominal
compression, saline infusion, or prone positioning.
Materials and Methods
Patients
Ninety-eight collecting systems and ureters of 50 consecutive patients (27
men and 23 women; age range, 25-86 years; mean age, 56.8 years) who had
dedicated urinary tract CT examinations were evaluated. Two patients had
unilateral distal ureteral stones with mild ipsilateral hydronephrosis. The
renal collecting system and ureter of the affected side in these two patients
were excluded from this study. The indications for the examination included
hematuria (n = 34), previous or suspected renal mass (n =
11), history of bladder cancer (n = 1), suspected urinary tract
infection (n = 1), suspected urinary obstruction (n = 1),
urinary calculus (n = 1), and reflux nephropathy (n = 1).
All examinations were clinically requested, and approval for retrospective
review of the medical records and CT studies was obtained from our
institutional review board.
CT Technique
All examinations were performed on a Sensation 16 scanner (Siemens Medical
Solutions). After being kept on NPO (nothing by mouth) status for at least 2-3
hr, each patient ingested 750-1,000 mL of water over a 15-20 min period before
scanning began. Nearly all patients were able to drink the entire 750-1,000 mL
of water without difficulty.
For administration of IV contrast material, a 20-gauge peripheral line was
inserted into an antecubital fossa vein and 120 mL of iohexol (Omnipaque 350,
Amersham Health) was injected at an injection rate of 3 mL/sec. The protocol
for evaluation of the patients included the following 3-phase scanning
procedure: unenhanced scan through the kidneys to just below the symphysis
pubis, arterial phase scan of the kidneys at 25 sec after IV contrast
injection, and excretory-phase scan from the kidneys to just below the
symphysis pubis at 240 sec after IV contrast injection.
For unenhanced scans, parameters were 3-mm slice thickness and 3-mm
increments. For arterial and excretory phases, parameters were 0.75-mm slice
thickness and 0.5-mm reconstruction increments. Parameters for
contrast-enhanced scans were 16 x 0.75 mm detector collimation, 12 mm
per rotation table speed, 0.5-sec gantry rotation speed, 120 kVp, and 120-150
mAs.
All image data were reconstructed with the body soft-tissue algorithm and
sent to a freestanding commercially available workstation (Leonardo, Siemens
Medical Solutions) using InSpace software (Siemens) in the original resolution
of 512 x 512. Excretory-phase data were used to evaluate the degree of
opacification of the collecting system and ureters. InSpace software is the
volume imaging application for interactive viewing of volume data available on
the Leonardo workstation. It provides reviewers real-time axial scrolling,
interactive multiplaner reformatting, and 3D rendering for review of
images.
View larger version (112K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1A —35-year-old woman with history of chronic hematuria. Complete
opacification of bilateral renal collecting systems and ureters shown on
anterior volume rendered 3D image. Opacification scores by both reviewers were
3 at bilateral calyces/infundibula, bilateral renal pelves, bilateral upper
ureters, and bilateral lower ureters. Opacification score 3 = complete
opacification, 2 = near complete (80-99%) opacification, 1= poor ( 79%)
opacification.
|
|
View larger version (19K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2 —Opacification scores at each segment obtained by average of
two reviewers. Opacification score 3 (black) = complete
opacification, 2 (gray) = near complete (80-99%) opacification, 1
(white) = poor ( 79%) opacification. CI = calyx and infundibulum,
RP = renal pelvis, UP = upper ureter, LU = lower ureter.
|
|
View larger version (128K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3A —73-year-old woman with infiltrating high-grade transitional
cell carcinoma of right renal pelvis. Filling defect (arrow) in right
renal pelvis represents high-grade transitional cell carcinoma shown on
anterior volume rendered 3D image. Right ureteral stent is in place. Right
ureter is moderately dilated. Opacification scores: 2 and 3 at right
calyx/infundibulum by each reviewer, respectively; 2 at left
calyx/infundibulum; and 3 at bilateral renal pelves and ureters by both
reviewers. Opacification score 3 = complete opacification, 2 = near complete
(80-99%) opacification, 1 = poor ( 79%) opacification.
|
|
View larger version (137K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3B —73-year-old woman with infiltrating high-grade transitional
cell carcinoma of right renal pelvis. Anterior coronal reformatted image shows
soft-tissue mass (arrow) in right renal pelvis representing
high-grade transitional cell carcinoma.
|
|
View larger version (121K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3C —73-year-old woman with infiltrating high-grade transitional
cell carcinoma of right renal pelvis. Oblique axial reformatted image shows
mass in right renal pelvis invading into hilar adipose tissue and kidney.
Lower pole calyx is markedly stretched and narrowed (arrow).
|
|
Image Analysis
Two radiologists reviewed the excretory-phase data sets at the workstation
and evaluated degree of opacification of the renal collecting system and
ureters independently. Reformatted and 3D images were created by each reviewer
at the time of image analysis using InSpace software, which combined axial,
sagittal, and coronal reformatted images with interactive 3D imaging. The
degree of opacification was determined using axial scrolling and reformatted
and 3D imaging (mostly volume rendering technique) comprehensively. These
techniques were not compared in this study.
Each urinary tract was divided into four segments: renal calices and
infundibula, renal pelvis, upper ureter above the iliac crest, and lower
ureter below the iliac crest. The degree of opacification for each segment was
evaluated using a scale from 1 to 3. Scores were 3 = complete opacification of
the entire renal collecting system or ureter, 2 = near complete (80-99%)
opacification of the renal collecting system or ureter, and 1 = no or poor
( 79%) opacification of the renal collecting system or ureter.
Interobserver agreement was assessed using kappa statistics. Values of kappa
greater than 0.75 indicate strong agreement beyond chance, values between 0.40
and 0.79 indicate fair to good, and values below 0.40 indicate poor agreement.
Abnormal findings were also recorded if present.
View larger version (132K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4A —48-year-old woman with history of reflux nephropathy and
recurrent renal infections. Volume loss of right kidney and bilateral caliceal
bluntings associated with focal thinning of adjacent renal cortex are shown on
anterior volume rendered 3D image. Contrast layers within dependent portion of
bladder are also shown. Opacification scores: 2 and 3 at bilateral
calyces/infundibula by each reviewer, respectively; and 3 at bilateral renal
pelves and ureters by both reviewers. Opacification score 3 = complete
opacification, 2 = near complete (80-99%) opacification, 1 = poor ( 79%)
opacification.
|
|
Results
Among 98 renal collecting systems and ureters, the opacification scores of
the calyx and infundibulum by each of the two reviewers were 3 (complete
opacification) in 61% and 53%, respectively (average, 57%) (Figs.
1A and
1B); 2 (near complete
opacification) in 34% and 42%, respectively (average, 38%); and 1 (poor
opacification) in 5% and 5%, respectively (average, 5%). The opacification
scores of the renal pelvis by each reviewer were 3 in 93% and 96%,
respectively (average, 94.5%); 2 in 5% and 2%, respectively (average, 3.5%);
and 1 in 2% and 2%, respectively (average, 2%). The opacification scores of
the upper ureter by each reviewer were 3 in 79% and 77%, respectively
(average, 78%); 2 in 7% and 6%, respectively, (average, 6.5%); and 1 in 14%
and 17%, respectively (average, 15.5%). The opacification scores of the lower
ureter by each reviewer were 3 in 55% and 62%, respectively (average, 58.5%);
2 in 21% and 5%, respectively (average, 13%); and 1 in 23% and 33%,
respectively (average: 28%) (Fig.
2). The two reviewers obtained 
values for the degree of
opacification of the calyx and infundibulum of 0.46, renal pelvis 0.72, upper
ureter 0.86, and lower ureter 0.61.
Four patients had mild dilatation of the renal collecting system and ureter
on one side. The affected side of the renal collecting system and ureter was
completely or nearly completely opacified in these four patients. One patient
had a transitional cell carcinoma of the renal pelvis and had a ureteral stent
(Figs. 3A,
3B, and
3C), one patient had a benign
ureteral stricture, and the other two patients had an external compression on
the ureter—one patient from the iliac artery and the other from a large
bladder diverticulum.
Other abnormal findings included bilateral calyceal blunting with cortical
scarring because of recurrent reflux nephropathy in one patient (Figs.
4A and
4B), bilateral duplicated renal
collecting system in one patient, and stretching of the renal collecting
system because of parapelvic cysts in three patients. A solid renal mass was
found in six patients.
Discussion
Various techniques have been used successfully to achieve optimal
distention and opacification of the renal collecting system and ureters. To
achieve optimal opacification, McNicholas et al.
[1] applied abdominal
compression and reported that there was a significantly higher opacification
score of the mid to distal ureter. To achieve better distention of the renal
collecting system and ureters, Caoili et al.
[4] also applied abdominal
compression and reported that measured renal collecting system distention was
significantly greater in patients who received abdominal compression.
However, abdominal compression may be contraindicated and thus may not be
applied in some patients, such as those with abdominal aortic aneurysm
[8]. With prone positioning,
McNicholas et al. [1] reported
that there was a significantly higher opacification score of the mid ureter
compared with supine positioning. McTavish et al.
[6] reported that with
supplemental 250 mL of IV saline solution administration, there were
significantly improved mean opacification scores in the distal ureters in
procedures performed with prone or supine positioning.
When supplemental saline was administered, 94% of all segments achieved
greater than 50% opacification. However, there was no statistically
significant difference between supine and prone positioning with this
technique [6]. Nolte-Ernsting
et al. [7] reported that with a
250-mL saline infusion, there was complete or near-complete opacification of
the ureters in 60% and pelvicaliceal system in 90% in 10 ureters and 10
pelvicaliceal systems in five patients, which further improved to 94% and 100%
with IV administration of 10 mg of furosemide in 32 ureters and 32
pelvicaliceal systems in 16 patients.
In our series, oral hydration was devised as a simple substitution for the
previously reported techniques of abdominal compression, saline infusion, and
furosemide administration and allowed for a minimal amount of wait time for
the patient and reduced the effect on workflow and room utilization. With the
average CT acquisition with 16-MDCT scanners in the range of 10-30 sec, a
short delay that does not compromise study quality is a welcome benefit to a
smooth and efficient clinical operation in 32 ureters and 32 pelvicaliceal
sytems in 16 patients.
There were several limitations of our study. First, in this study we were
unable to compare the results with those of patients who did not ingest water.
We used oral hydration not only to increase opacification of the renal
collecting system and ureter but also to reduce the possibility of renal
toxicity and to improve evaluation of stomach and bowel as negative oral
contrast. Because of the advantages of oral hydration, we thought it would be
unethical in clinical practice to use a control group that did not have oral
hydration. Second, four patients had mild unilateral hydronephrosis and
hydroureter, which may account for better opacification scores. Third, we used
relatively short delay time of 4 min to obtain excretory-phase images and were
unable to make a comparison with a longer delay.
In conclusion, excretory-phase CT with oral hydration opacified the
calyx/infundibulum completely in 57% and nearly completely in 38%, opacified
the renal pelvis completely in 94.5% and nearly completely in 3.5%, and
opacified the upper ureter completely in 78% and nearly completely in 6.5% by
the average of two reviewers. The distal ureter was the most difficult segment
to opacify, but it was opacified completely in 58.5% and nearly completely in
13% of the cases.
References
- McNicholas MMJ, Raptopoulos VD, Schwartz RK, et al. Excretory phase
CT urography for opacification of the urinary collecting system.
AJR 1998; 170:1261
-1267[Abstract/Free Full Text]
- Caoili EM, Cohan RH, Korobkin M, et al. Urinary tract
abnormalities: initial experience with multi-detector row CT urography.
Radiology 2002;222
: 353-360[Abstract/Free Full Text]
- Chow LC, Sommer FG. Multidetector CT urography with abdominal
compression and three-dimensional reconstruction. AJR2001; 177:849
-855[Free Full Text]
- Caoili EM, Cohan RH, Korobkin M, et al. Effectiveness of abdominal
compression during helical renal CT. Acad Radiol2001; 8:1100
-1106[CrossRef][Medline]
- Heneghan JP, Kim DH, Leder RA, et al. Compression CT urography: a
comparison with IVU in the opacification of the collecting system and ureters.
J Comput Assist Tomogr 2001;25
: 343-347[CrossRef][Medline]
- McTavish JD, Jinzaki M, Zou KH, et al. Multi-detector row CT
urography: comparison of strategies for depicting the normal urinary
collecting system. Radiology 2002;225
: 783-790[Abstract/Free Full Text]
- Nolte-Ernsting CC, Wildberger JE, Borchers H, et al. Multi-slice CT
urography after diuretic injection: initial results. Rofo Fortschr
Geb Rontgenstr Neuen Bildgeb Verfahr 2001;173
: 176-180[Medline]
- Hattery RR, Williamson B, Hartman GW, et al. Intravenous urographic
technique. Radiology 1988;167
: 593-599[Abstract/Free Full Text]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
Top
Introduction
Materials and Methods
