AJR 2004; 183:1691-1696
© American Roentgen Ray Society
Antegrade MDCT Pyelography for the Evaluation of Patients with Obstructed Urinary Tract
Eduard Ghersin1,
Olga R. Brook1,
Shimon Meretik2,
Joseph K. Kaftori1,
Amos Ofer1,
Marco A. Amendola3 and
Ahuva Engel1
1 Department of Diagnostic Imaging, Rambam Medical Center, PO Box 9602, Haifa
31096, Israel.
2 Department of Urology, Rambam Medical Center, Haifa 31096, Israel.
3 Department of Radiology, University of Miami, Miami, FL 33136.
Received December 29, 2003;
accepted after revision March 16, 2004.
Address correspondence to E. Ghersin.
Abstract
OBJECTIVE. The purpose of this study was to design an alternative
imaging technique to CT urography in patients with high-grade urinary tract
obstruction, with or without impaired renal function, that uses the superior
resolution of MDCT and avoids IV contrast material administration.
CONCLUSION. Antegrade MDCT pyelography is an alternative imaging
technique to CT urography in patients with high-grade urinary tract
obstruction with or without impaired renal function. It enables accurate
diagnosis of the level of obstruction, as well as its etiology, including
nephroureterolithiasis, urothelial tumors, primary congenital megaureter,
uretero-pelvic junction stenosis, ureteral edema, ureteral stricture,
retroperitoneal fibrosis, and pelvic lymphadenopathy.
Introduction
CT urography has gradually evolved as an accepted method for comprehensive
assessment of patients with flank pain or hematuria
[1–5].
The main advantage of CT urography over excretory urography is its ability to
show the urinary tract lumen, urinary tract walls, and surrounding tissues.
However, imaging of patients with marked urinary tract obstruction using
various CT urography techniques remains a problem because of poor and
insufficient contrast material excretion. Furthermore, the application of CT
urography is limited in patients with impaired renal function. We describe a
new technique that we have termed "antegrade MDCT pyelography" as
an imaging technique that is alternative to or complementary to CT urography
in patients with high-grade unilateral and bilateral urinary tract obstruction
with or without impaired renal function.
Materials and Methods
Between December 2002 and October 2003, antegrade MDCT pyelography was
performed in a group of eight women and 13 men, 20–81 years old (average
age, 61.9 years), with high-grade urinary tract obstruction, the cause of
which was equivocal on the basis of previously performed conventional
antegrade pyelography (17 patients) or other imaging studies (four patients).
Twelve patients had associated impaired renal function
(Table 1). We examined 21
native kidneys and one transplanted kidney (in one patient, two native kidneys
were examined). All examinations were performed, reconstructed, and reported
at one institution—Rambam Medical Center, Haifa, Israel—by an
attending radiologist subspecializing in body imaging, assisted by a
first-year resident. First, unenhanced MDCT was performed to verify the
presence of urolithiasis using an IDT 16-slice or Mx8000 Quad MDCT scanner
(Philips Medical Systems). The following imaging and reconstruction parameters
were used respectively: collimation, 16 x 1.5 mm; pitch, 0.95; 120 kV;
300 mAs; slice width, 3 mm; increment, 1.5 mm; and collimation, 4 x 2.5
mm; pitch, 0.875; 120 kV; 300 mAs; slice width, 3.2 mm; increment, 1.6 mm.
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TABLE 1 Correlation Among Antegrade MDCT Pyelography, Conventional Imaging,
Surgery, and Clinical Follow-Up in 21 Patients
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Immediately afterward, we injected 20–50 mL of diluted nonionic
iodinated contrast material (Iomeron [iomeprol], 300 mg I/mL, Bracco) directly
into the renal pelvis through a previously placed percutaneous nephrostomy
catheter (17 patients) or by direct puncture of the renal collecting system
under CT guidance using a 5-French Ring biliary needle (Cook) (three
patients). The contrast material was diluted with sterile saline at a volume
ratio of 1:9, resulting in a diluted solution containing 30 mg I/mL. The exact
amount injected was determined preliminarily by the degree of urinary tract
dilatation and by patient tolerance. To avoid collection-system
overdistention, we routinely aspirated urine from the collecting system before
injecting diluted contrast material. After the injection, a preliminary
assessment of adequate urinary tract opacification was made on the basis of a
new CT scout image followed by a second MDCT of the entire urinary system with
the patient in the prone position, using the same imaging and reconstruction
parameters. Both volumetric data sets were reconstructed on an MxView
Workstation (Philips Medical Systems) using coronal oblique and sagittal thin-
and thick-slab 2D reformations. In selected patients for better ureteral
delineation, the second volumetric data set was additionally reformatted using
volume rendering and curved multiplanar reformations. Source axial images and
all reformations were evaluated on a PACS (Philips Medical Systems) using
various window settings. The initial prospectively reported imaging findings
were retrospectively correlated with conventional imaging studies, surgical
and pathologic findings, and clinical outcome by an attending radiologist
subspecializing in body imaging, assisted by a first-year resident.
Results
All examinations were diagnostic. Antegrade MDCT pyelography was well
tolerated by all patients with the exception of one with a transplanted kidney
evaluated for hydroureteronephrosis accompanied by impaired renal function.
This patient subsequently developed a urinary tract infection that responded
well to systemic antibiotic treatment. Antegrade MDCT pyelography accurately
diagnosed the level of urinary tract obstruction in all patients. A variety of
diseases of the urinary tract were accurately identified
(Table 1), among them
nephrolithiasis, depicted as mobile filling defects after the injection of
diluted contrast material (hyperdense on the initial unenhanced CT scan);
ureterolithiasis, displayed by dilatation of the ureteral lumen proximal to an
obstructing stone; ureteral transitional cell carcinoma, shown by fixed
ureteral filling defects of soft-tissue densities or as irregularity and focal
thickening of ureteral walls (Fig.
1A,
1B,
1C); bladder transitional cell
carcinoma and recurrent transitional cell carcinoma after radical cystectomy,
depicted by irregularity and focal thickening of bladder and ileal pouch walls
with adjacent fat stranding (Figs.
2A,
2B and
3A,
3B); congenital megacalyces
associated with primary congenital megaureter, displayed by an abnormally
increased number of calyces with absent calyceal cupping and an abnormally
dilated, convoluted ureter with smoothly tapered narrowing of its intravesical
portion (Fig. 4A,
4B); and retroperitoneal
fibrosis, depicted by ureteral medial deviation and circumferential focal
narrowing caused by a retroperitoneal plaque (Fig.
5A,
5B,
5C).
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Fig. 1A. —68-year-old man after percutaneous nephrostomy due to left
hydronephrosis. Conventional antegrade pyelogram shows ureteral obstruction in
lower ureter (arrow) without filling defects or wall
irregularity.
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Fig. 1B. —68-year-old man after percutaneous nephrostomy due to left
hydronephrosis. Thin-slab sagittal (B) and curved multiplanar
(C) reformations depict two lesions in lower ureter (arrows),
focal thickening of posterior wall, and filling defect of soft-tissue density.
These lesions correlated with surgical and histopathologic findings of
multifocal transitional cell carcinoma of lower ureter.
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Fig. 1C. —68-year-old man after percutaneous nephrostomy due to left
hydronephrosis. Thin-slab sagittal (B) and curved multiplanar
(C) reformations depict two lesions in lower ureter (arrows),
focal thickening of posterior wall, and filling defect of soft-tissue density.
These lesions correlated with surgical and histopathologic findings of
multifocal transitional cell carcinoma of lower ureter.
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Fig. 2A. —71-year-old man after percutaneous nephrostomy due to right
hydronephrosis with history of invasive bladder transitional cell carcinoma.
Axial CT scan obtained at level of ureterovesical junction after right
antegrade MDCT pyelography shows small exophytic bladder mass (dotted
arrow) that involves medial wall of distal right ureter. Residual
ureteral lumen (solid arrows) is opacified after injection of
contrast material through nephrostomy catheter.
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Fig. 2B. —71-year-old man after percutaneous nephrostomy due to right
hydronephrosis with history of invasive bladder transitional cell carcinoma.
IV-contrast-enhanced standard abdominal axial CT scan after oral contrast
material administration at parallel anatomic position obtained 6 weeks after
A depicts enlargement of exophytic bladder mass without delineation of
distal ureteral lumen due to delayed contrast excretion. Note normal left
ureterovesical junction (short solid arrow).
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Fig. 3A. —65-year-old man 6 months after radical cystectomy with ileal
conduit due to invasive bladder transitional cell carcinoma. Previous
loopogram and sonogram (not shown) failed to opacify left ureter and renal
collecting system and showed moderate left hydronephrosis, respectively.
Antegrade MDCT pyelogram was obtained through biliary sheath needle
(arrow) placed in left renal collecting system under CT guidance.
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Fig. 3B. —65-year-old man 6 months after radical cystectomy with ileal
conduit due to invasive bladder transitional cell carcinoma. Previous
loopogram and sonogram (not shown) failed to opacify left ureter and renal
collecting system and showed moderate left hydronephrosis, respectively. In
right pelvis, left hydroureter is visible because of soft-tissue mass
(dotted black arrow) at anastomosis between distal left ureter
(dotted white arrow) and ileal conduit (solid white arrow).
Also, small fluid collection is seen posterior to anastomotic mass, probably
representing small urinoma (solid black arrow). Findings are
consistent with local tumor recurrence.
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Fig. 4A. —20-year-old man with mild renal failure (creatinine level,
1.7 mg/dL) and sonographic evidence of marked right hydronephrosis and
hydroureter associated with left renal agenesis (not shown). Antegrade MDCT
pyelography was performed through biliary sheath needle placed in right renal
collecting system under CT guidance. Volume-rendered reformation depicts
increased number of calyces with absent calyceal cupping (solid
arrow) and abnormally dilated convoluted ureter (dotted
arrow).
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Fig. 4B. —20-year-old man with mild renal failure (creatinine level,
1.7 mg/dL) and sonographic evidence of marked right hydronephrosis and
hydroureter associated with left renal agenesis (not shown). Antegrade MDCT
pyelography was performed through biliary sheath needle placed in right renal
collecting system under CT guidance. Curved multiplanar reformation shows
markedly dilated ureter with smoothly tapered narrowing of its intravesical
portion (arrow). Findings are consistent with congenital megaureter
and megacalyces.
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Fig. 5A. —49-year-old woman after bilateral percutaneous nephrostomy
due to severe hydronephrosis and renal failure. Thick-slab coronal multiplanar
reformation depicts bilateral medial deviation with focal narrowing of both
mid ureters at level of L4–L5 (arrow).
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Fig. 5B. —49-year-old woman after bilateral percutaneous nephrostomy
due to severe hydronephrosis and renal failure. Thin-slab curved multiplanar
reformations projected in coronal (B) and sagittal (C) planes
depict marked focal luminal narrowing of right ureter (white arrows)
caused by discrete retroperitoneal plaque (black arrow, C).
Findings are consistent with idiopathic retroperitoneal fibrosis and were
confirmed on contrast-enhanced CT and MRI (not shown).
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Fig. 5C. —49-year-old woman after bilateral percutaneous nephrostomy
due to severe hydronephrosis and renal failure. Thin-slab curved multiplanar
reformations projected in coronal (B) and sagittal (C) planes
depict marked focal luminal narrowing of right ureter (white arrows)
caused by discrete retroperitoneal plaque (black arrow, C).
Findings are consistent with idiopathic retroperitoneal fibrosis and were
confirmed on contrast-enhanced CT and MRI (not shown).
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Discussion
Since the advent of MDCT technology, CT urography is gaining a dominant
role as an expeditious, robust, and comprehensive imaging technique for the
entire urinary system, including native and transplanted kidneys, collecting
systems, ureters, and the urinary bladder
[1–6].
The superior spatial and contrast resolution of MDCT enables the accurate
diagnosis of various diseases, including urolithiasis, renal and uroepithelial
masses, and congenital anomalies. In addition, CT urography offers better
opacification of the collecting system and ureters in comparison with
excretory urography, as shown by Heneghan et al.
[7]. These facts have led some
investigators to consider abandoning other traditionally accepted imaging
techniques like excretory urography and to accept CT urography as the primary
initial comprehensive imaging technique for urinary tract disease
[8,
9]. Etemad et al.
[10] advocate a more selective
use of CT urography in patients older than 40 years with hematuria because of
a higher incidence of tumors and calculus disease in this age group.
Nevertheless, CT urography has some limitations, among them the requirement of
IV iodinated contrast material administration and the reliance on adequate
renal function for the opacification of the collecting systems, ureters, and
urinary bladder. These restrictions limit the use of CT urography in patients
with marked urinary tract obstruction and moderate to severe impairment of
renal function. MR urography is also a highly useful imaging technique in
obstructed urinary systems, especially when the obstruction is of noncalculous
origin [11]. Nevertheless,
although static fluid MR urography can define the level of obstruction, it is
not adequate for defining the cause of obstruction. For this purpose,
conventional MRI sequences and excretory MR urography after the administration
of gadopentate dimeglumine are essential. These findings suggest that although
MR urography, as opposed to CT urography, can be safely performed in patients
with renal failure, it is suboptimal for the evaluation of urinary obstruction
of calculous origin, and like CT, urography relies on adequate renal function
for the opacification of the collecting systems, ureters, and urinary
bladder.
In an attempt to overcome these limitations of CT urography and MR
urography, we developed an imaging technique that does not require IV
injection of contrast material, does not rely on adequate renal function, and
can be safely performed in patients with obstructed urinary tracts and
impaired renal function. CT-guided antegrade pyelography and percutaneous
nephrostomy have been described previously by Haaga et al.
[12] in the early era of CT.
In their article, CT merely served for guiding the insertion of the needle
into the renal collecting system and not for diagnostic purposes. We decided
to combine their idea with current MDCT technology and came up with a new
imaging technique that we named "antegrade MDCT pyelography." As
shown, antegrade MDCT pyelography accurately depicts the level of urinary
tract obstruction and in most instances has enabled us to determine the cause
of obstruction.
Although highly accurate and robust, antegrade MDCT pyelography is a
potentially minimally invasive technique that requires puncturing the renal
collecting system to inject the diluted contrast material. In our experience,
careful CT guidance and the use of 5-French biliary sheath needles and a
sterile technique have enabled us to avoid any significant complications such
as bleeding or secondary urinary tract infection, except in one patient with a
urinary tract infection and a transplanted kidney. On the basis of our
experience, we suggest that in selected patients, such as those who are
immunocompromised and have a transplanted kidney, preprocedural antibiotic
treatment is indicated.
The limitations of our study include a relatively small study group, its
retrospective nature and the heterogeneity of diseases, and types of
follow-up. Taking into account these limitations, we found that the main
indications for antegrade MDCT pyelography are as follows: CT urography
examinations are nondiagnostic because of poor or absent contrast material
excretion as a result of highgrade urinary tract obstruction; severely
obstructed urinary tracts are present in conjunction with moderate to severe
impairment of renal function; and there is an equivocal diagnosis after the
placement of a percutaneous nephrostomy catheter to relieve urinary tract
obstruction.
In conclusion, antegrade MDCT pyelography provides superior anatomic
details of various diseases involving the renal collecting system, ureter, and
bladder. It can be safely used as an imaging technique complementary to
unenhanced CT or CT urography whenever the findings are equivocal or as an
alternative technique in patients with high-grade urinary tract obstruction or
impaired renal function.
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Abstract
Introduction
