| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Department of Radiology, Medical College of Wisconsin, Froedtert Hospital,
9200 W Wisconsin Ave., Milwaukee, WI 53226.
2 Department of Urology, Medical College of Wisconsin, Milwaukee, WI
53226.
3 Medical College of Wisconsin, Milwaukee, WI 53226.
Received March 6, 2004;
accepted after revision April 15, 2004.
Address correspondence to Gary Sudakoff
(gsudakof{at}mcw.edu).
Abstract
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
MATERIALS AND METHODS. Thirty CTU and contrast-enhanced CTDR examinations were performed in 24 patients who underwent cystectomy for bladder cancer. Indications for evaluation included hematuria, tumor surveillance, or suspected diversion malfunction. All examinations were evaluated without knowledge of the stage or grade of a patient's tumor and were compared with the clinical records. Opacification of the urinary collecting system was evaluated with 3D CTU alone, contrast-enhanced CTDR alone, and combined CTU and CTDR.
RESULTS. Nine abnormalities were identified including distal ureteral strictures (n = 4), vascular compression of the mid left ureter (n = 1), scarring of the mid right pole infundibulum (n = 1), bilateral hydronephrosis and hydroureter (n = 1), urinary reservoir calculus (n = 1), and tumor recurrence invading the afferent limb of the neobladder (n = 1). Eight of the nine detected abnormalities were surgically or pathologically confirmed. All abnormalities were identified on all three imaging techniques but were best seen on 3D CTU and enhanced CTDR images. Incomplete opacification of the urinary collecting system occurred in 17 patients with CTU alone, 12 patients with contrast-enhanced CTDR alone, and nine patients with combined CTU and contrast-enhanced CTDR. Compared with CTU alone, the combined technique of 3D CTU and contrast-enhanced CTDR improved opacification by a statistically significant difference (p = 0.037).
CONCLUSION. CTU with 3D rendering can accurately depict both normal and abnormal postoperative findings in patients with urinary diversions. Adding enhanced CTDR can improve visualization of the urinary collecting system.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Complications of urinary diversions are numerous and include anastomotic leaks, hemorrhage, upper urinary tract infection, abscess formation, ischemia and obstruction, deterioration of renal function, and tumor recurrence [2–9]. Radiologic evaluation of patients with urinary diversions to assess postoperative complications, particularly tumor recurrence, can be difficult and technically challenging. Excretory urography and fluoroscopic retrograde contrast injections of the diversion (fluoroscopic loopography or pouchography) historically have been the two main imaging methods for evaluating urinary diversions [2, 10–15]. Although these techniques may reveal some postoperative complications, they also have significant limitations, particularly in showing tumor recurrence.
CT loopography and IV contrast–enhanced CT have been described as effective techniques for identifying both normal postoperative findings and complications after urinary diversion [2, 3, 16]. Examinations performed on single-detector scanners are generally limited by scanning speed, slice collimation, and the inability to perform multiphase scanning or 3D rendering of imaging data. CT urography (CTU) is a relatively new technique using MDCT to obtain rapidly acquired, multiphase scans for near isotropic data sets [17, 18]. These data sets can be transferred to an independent workstation for multiplanar 3D rendering of the genitourinary system.
The purpose of this study was to evaluate patients with urinary diversions who presented with hematuria or possible diversion malfunction, or who were undergoing surveillance for tumor recurrence to determine whether CTU combined with contrast-enhanced CT digital radiography (CTDR) could be used to accurately identify normal postoperative findings, abnormalities affecting the diversion, and other extraurinary abnormalities.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
All patients undergoing CTU were scanned using 8- or 16-MDCT scanners (LightSpeed Ultra and LightSpeed Pro 16, GE Healthcare). All scans were performed with the patient prone in an attempt to improve opacification of the urinary collecting systems. The examination was performed in three phases: Before scanning, a 20-gauge IV catheter was inserted into an appropriate upper-extremity vein. The patients were then placed on the scanner table in the prone position. The first phase was a noninfused scan acquired from the costovertebral angles through the floor of the pelvis with 5-mm collimation and a pitch of 1.35:1 or 1.375:1 (8- or 16-MDCT scanners, respectively). The second phase began with the injection of 40 mL of IV contrast material (iohexol, Omnipaque 300, Amersham Health) via a power injector at a rate of 1.5 mL/sec. After a delay of 10 min, an additional 110 mL of contrast material was injected by a power injector at a rate of 3 mL/sec. Scanning began 100 sec after the start of the second contrast injection and was performed from the dome of the diaphragm through the floor of the pelvis. Scans in this combined nephropyelographic stage were obtained during a single breath-hold, with 1.25-mm detector collimation and 1.34:1 or 1.375:1 pitch and were reconstructed with an overlap of 50%. The third phase consisted of a contrast-enhanced CTDR scan of the abdomen and pelvis obtained 1 min after axial imaging (300 mAs, 80 kVp, Rad View Scout, GE Healthcare). The enhanced CTDR study was monitored by the attending physician to determine if the urinary collecting system and diversion were adequately opacified. No more then three enhanced CTDR images were acquired per examination (obtained 3 and 5 min after axial imaging). These data were then transferred to a workstation (Advantage 4.2, GE Healthcare) for 3D rendering.
Three-dimensional rendering was performed using the data acquired during the nephropyelographic phase (phase 2) in the kidneys, ureters, and urinary reservoir using maximum-intensity-projection and average-intensity-projection techniques. Reformatted images routinely included coronal images of both kidneys, oblique images of the kidneys and ureters individually, and coronal and oblique images of the urinary diversion with particular attention to the ureteroenteric anastomosis.
The CTU and enhanced CTDR images were reviewed by a single genitourinary radiologist who was unaware of the patient's history or physical findings, tumor grade or stage, or the presence of diversion malfunction. The noninfused CTU images were reviewed for the presence of urinary calculi, nonurinary calcifications, renal cystic lesions, hydronephrosis, and perinephric collections. The contrast-enhanced axial and 3D-rendered images obtained during the nephropyelographic phase (phase 2) were evaluated for the presence of cystic or solid renal lesions, congenital genitourinary anomalies, papillary abnormalities (medullary sponge kidney disease and papillary necrosis), or uroepithelial lesions of the urinary collecting system. Extrinsic mass lesions affecting the kidneys, ureters, or urinary diversion and extraurinary abnormalities were recorded.
The enhanced CTDR images were compared with the 3D-rendered CTU images to determine whether abnormalities seen on CTU images could be seen on enhanced CTDR images and whether one technique was superior or complementary to the other. We also compared the two types of images in the opacification of the urinary collecting system and evaluated whether one technique was superior or complementary to the other. The urinary collecting system was separated into segments: the intrarenal collecting system, proximal ureter (the renal pelvis and the proximal 2 cm of the ureter), mid ureter (from the proximal 2 cm of the ureter up to the iliac crest), distal ureter (from the iliac crest to the urinary reservoir), ureteroenteric anastomosis, and urinary reservoir. We noted whether opacification of a collecting system segment was present or absent on the images acquired with each technique and whether opacification of a segment could be identified on images acquired with the combined techniques. Partially opacified ureteral segments were graded as being nonopacified. The locations of nonopacified segments on CTU images were recorded and correlated with any changes in opacification on enhanced CTDR images. The location of any abnormality affecting the urinary diversion was also documented. Segments with ureteral strictures or intrinsic or extrinsic masses that affected the collecting system or reservoir were identified on CTU images; these images were then compared with their corresponding enhanced CTDR images to determine if one technique was superior to the other in depicting these abnormalities.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
|
|
|
|
|
|
|
|
The combined imaging technique of CTU and enhanced CTDR revealed nine abnormalities affecting the urinary diversion: distal right ureteral strictures (n = 3), distal left ureteral stricture (n = 1), focal narrowing of the mid left ureter produced by compression of the overlying inferior mesenteric artery and vein (n = 1), focal defect in the infundibulum of the mid right pole from a prior indwelling nephrostomy tube (n = 1), bilateral hydronephrosis and hydroureter (n = 1), 1.5-cm calculus within the urinary reservoir (n = 1), and tumor recurrence in the pelvis invading the afferent limb of the neobladder (n = 1) (Figs. 5A, 5B, 6A, 6B, 7A, and 7B). Of the nine detected radiographic abnormalities, seven (78%) were clinically significant and were either surgically or pathologically confirmed. On a 6-month follow-up CTU examination, the focal infundibular filling defect had resolved and was presumed to have been secondary to inflammation from a prior indwelling nephrostomy tube. The remaining patient, with focal narrowing of the mid left ureter secondary to vascular compression by the inferior mesenteric artery and vein, had no clinical or radiologic evidence of obstruction and has not undergone surgical revision. This patient continues to have normal renal function 2 years after surgery. The patient with bilateral hydronephrosis and hydroureter had massive reflux but no deterioration of renal function, and the condition was managed with bilateral indwelling ureteral stents. All nine abnormalities were identified on all three imaging techniques (axial CT, 3D-rendered MIP and AIP images and enhanced CTDR), but were seen best on 3D-rendered CTU and enhanced CTDR. Abnormalities were identified equally well with both techniques. Additional abnormalities not related to diversion abnormalities included bilateral nonobstructing renal stones in six patients, simple renal cysts in five patients, a complex renal cyst (Bosniak category 2F) in one patient, gallstones in two patients, and a 2.0-cm splenic artery aneurysm in one patient.
|
|
|
|
|
|
Total opacification of the entire genitourinary collecting system, ureteroenteric anastomosis, and urinary reservoir occurred in 13 of 30 studies (43.3%) by CTU alone and in 18 of 30 studies (60%) with enhanced CTDR alone. Combining enhanced CTDR with CTU allowed total opacification in an additional eight studies. Therefore, the combination of these two techniques depicted total opacification in 21 (70%) of 30 studies (Table 1). The number of enhanced CTDR images acquired per examination was as follows: one in four examinations, two in 18 examinations, and three in eight examinations.
|
The middle and distal left ureteral segments and the left ureteroenteric anastomosis were the most common sites that failed to opacify on either CTU alone, enhanced CTDR, or combined CTU and enhanced CTDR. Total opacification failed to occur on CTU alone in 17 (57%) of 30 studies. Forty-five sites of incomplete opacification were identified in this group, with 31 (68.8%) of these sites involving the left ureter or left ureteroenteric anastomosis (middle ureter, n = 6; distal ureter, n = 14; and ureteroenteric anastomosis, n = 11). The remaining 14 sites included the right ureter (middle ureter, n = 4; distal ureter, n = 4; and ureteroenteric anastomosis, n = 4), and urinary reservoir (n = 2) (Table 2).
|
Incomplete opacification occurred in 12 (40%) of 30 studies with enhanced CTDR alone. In this group, 49 sites of incomplete opacification were identified. Twenty-seven (55%) of the 49 sites involved the left ureter (middle ureter, n = 6; distal ureter, n = 12; and ureteroenteric anastomosis, n = 9). Twenty-one sites of incomplete opacification involved the right ureter (middle ureter, n = 4; distal ureter, n = 8; and ureteroenteric anastomosis, n = 9). The urinary reservoir was not opacified in one patient. The combination of CTU and enhanced CTDR failed to depict total opacification in nine (30%) of 30 studies. In this group, 24 sites of incomplete opacification were identified. Eighteen (75%) of the 24 sites involved the left ureter (middle ureter, n = 3, distal ureter, n = 9, and ureteroenteric anastomosis, n = 6). The remaining six sites (25%) involved the right ureter (middle ureter, n = 1, distal ureter, n = 3, and ureteroenteric anastomosis, n = 2) (Table 2).
A Pearson's chi-square test was performed to determine if total opacification of the urinary collecting system occurred using the combined technique of CTU plus enhanced CTDR compared with either CTU or enhanced CTDR alone. Compared with CTU alone, the combined technique of CTU plus enhanced CTDR improved total opacification, and difference was statistically significant (p = 0.037). Compared with enhanced CTDR alone, the combined technique of CTU plus enhanced CTDR also improved total opacification, but the difference was not statistically significant (p = 0.42). In evaluating nonopacified segments, a trend of improved segmental opacification was identified with the combined technique of CTU and enhanced CTDR, but it was not statistically significant compared with either technique alone.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Complications from urinary diversion, although uncommon, can occur and may be characterized as early or late. Early complications (< 30 days after surgery) relate directly to the surgical procedure itself; these include bowel complications such as ileus, obstruction, anastomotic leak, and ischemia; infectious complications such as urinary tract infection–pyelonephritis and pelvic or retroperitoneal abscess; postoperative fluid collections such as urinomas, hematomas, and lymphoceles; and ureterointestinal complications such as anastomotic leak, obstruction, or ischemia [21, 22]. Late complications include deterioration of renal function, ureteral reflux, hydronephrosis, stone formation (particularly in patients with ileal conduits), fistulas, metabolic disorders (metabolic acidosis, vitamin B12 deficiency), ureteral strictures, pouch necrosis, retroperitoneal fibrosis, and tumor recurrence [2, 3].
Tumor recurrence remains the most ominous late complication of cystectomy for bladder cancer and occurs more frequently in patients with high-grade and high-stage tumors. Recurrent bladder cancer may present as an obstructing ureteral stricture, pelvic lymphadenopathy, and pelvic soft-tissue mass with or without invasion of the urinary reservoir or obstructing stricture of the urethral–intestinal anastomosis. Several studies have shown that tumor recurrence is seen in 18% of patients with an orthotopic neobladder after cystectomy. Tumor recurrence at the urethral–intestinal anastomosis, as was reported by Studer and Zingg [4] and Studer et al. [5], occurs in 3% of patients with orthotopic neobladder [3].
Because of these potentially serious early- and late-term complications, some form of radiographic evaluation is mandatory in patients with urinary diversions. In most cases, early complications occurring after urinary diversion manifest themselves clinically and require urgent radiographic evaluation, usually with IV contrast–enhanced CT. Late complications of urinary diversion are more often insidious, and no consensus has been reached concerning which routine follow-up imaging protocols or technique is most useful (i.e., enhanced CT, fluoroscopic loopography, CT loopography, or IV urography). At the present time, follow-up imaging of patients with urinary diversions is generally directed by the personal philosophy of the referring urologist [23]. At our institution, we now use the following imaging guidelines to evaluate patients after urinary diversion for bladder cancer: All patients undergo CTU with enhanced CTDR 3 months after cystectomy to evaluate renal function, diversion malfunction, or tumor recurrence. Patients with pathologic stage T2 disease undergo CTU with enhanced CTDR 9 and 15 months after cystectomy and once annually thereafter. Patients with pathologic stage T3 disease undergo CTU with enhanced CTDR every 3 months for the first year and every 6 months the second year. If these patients are still clinically and radiographically free of disease, they undergo CTU with enhanced for CTDR annually.
CTU is a new technique using MDCT that permits multiplanar 3D rendering of the genitourinary system. Previous reports have shown that CTU can effectively image the genitourinary system and accurately detect and characterize abnormalities affecting the urinary system [17, 18, 24, 25]. Our use of a dual-contrast bolus allows imaging during a combined nephropyelographic phase and reduces the effective dose delivered by imaging performed in separate phases (noninfused, nephrographic, and pyelographic). Numerous advantages of CTU over IV urography and fluoroscopic loopography include improved detection and localization of urinary calculi, identification and characterization of small renal masses, and detection of uroepithelial lesions and extraurinary disease. Three-dimensionally rendered CTU images are useful for detecting papillary abnormalities such as tubular ectasia or papillary necrosis, congenital anomalies of the collecting system, and vascular anomalies affecting the renal pelvis or ureter and for surgical planning. CTU is generally not limited by a large body habitus, abundant stool, or bowel gas that may negatively affect the diagnostic quality of IV urography.
A major limitation to evaluating the urinary collecting system with CTU is incomplete opacification of the ureters, usually the distal ureters. McTavish et al. [18] found that when comparing opacification of CTU to IV urography in patients with intact urinary systems, the distal ureters were the most common segments that failed to opacify (because of ureteral peristalsis). In our experience, the mid and distal left ureteral segments and the left ureteroenteric anastomosis are the most frequent sites that fail to opacify in patients with urinary diversions evaluated with CTU or enhanced CTDR. The exact cause of the poor opacification of the mid and distal left ureter is not known. Possible explanations for this phenomenon include excessive mobilization of the left ureter when tunneling under the sigmoid mesentery to reach the urinary reservoir or ureteric kinking by the inferior mesenteric artery resulting in reduced peristalsis and thus poor opacification of this segment [6]. Although the mid and distal left ureters are the most commonly reported sites of ureteral stricture or obstruction in patients with urinary diversions, in our series more strictures were found to involve the distal right ureteral segment than the left (3:1 ratio). This difference was not statistically significant because of the small sample size.
Attempts to improve opacification of the ureters during CTU have met with some success. McTavish et al. [18] reported improved opacification of the distal ureters with the addition of a 250-mL saline bolus during the excretory phase. Others have incorporated the use of abdominal compression and release during the excretory phases of CTU to improve ureteral opacification [24]. During this study, enhanced CTDR was performed immediately after CTU to determine if the addition of this technique would improve opacification of the urinary collecting system compared to CTU alone.
Enhanced CTDR is a modification of conventional CTDR, which adds additional
filtering to the x- and y-axes and reduces artifacts between
soft tissue and bone interfaces while simultaneously improving resolution in
the z- axis. This additional filtering has the ultimate effect of
improving edge detail and giving the appearance and resolution of an image
that is nearly identical to those of a conventional radiograph. The effective
dose of enhanced CTDR is similar to that of conventional CTDR (
1 mSv).
The addition of enhanced CTDR to CTU proved to be effective in improving opacification of segments of the urinary diversion that may not have been seen with CTU alone. The addition of enhanced CTDR to CTU resulted in complete opacification in an additional eight (27%) of 30 studies, which was statistically significant (p = 0.037). Although enhanced CTDR could be used alone as a technique to visualize the urinary collecting system, the technique has many of the same limitations that affect IV urography and would not offer any additional information in evaluating patients with urinary diversions.
Our study has several limitations. First, our patient population was relatively small with a limited number of abnormalities detected. When compared with the surgical or pathologic findings, we found no false-positive or false-negative examinations in our study. However, a larger patient population may ultimately lead to increases in false-positive or false-negative findings using these techniques. Second, we did not evaluate whether the addition of a saline bolus, with or without the addition of enhanced CTDR, would have improved opacification of the urinary collecting system. We are currently evaluating this technique.
CTU with 3D rendering is becoming an increasingly useful technique for evaluating the genitourinary system. Using CTU to accurately detect and discriminate small urinary calculi, uroepithelial and renal lesions, and extraurinary disease without encountering the technical limitations of IV urography or fluoroscopic loopography is extremely attractive. This preliminary study shows the potential of CTU with enhanced CTDR rendering for assessing patients with urinary diversions for tumor surveillance or diversion malfunction. CTU with 3D rendering has the potential to be the imaging technique of choice for the initial evaluation of patients for hematuria, tumor surveillance, or diversion malfunction after cystectomy for bladder cancer.
Acknowledgments
We thank Drs. Guillermo F. Carrera and Robert Hellman for their editorial
assistance, Jan Staedler for her help in the preparation of this manuscript,
and Christine Sulok for medical illustrations.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  J Richenberg Haematuria Imaging, March 1, 2008; 20(1): 57 - 72. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. S. Sudakoff, D. P. Dunn, R. S. Hellman, M. A. Laguna, C. R. Wilson, R. W. Prost, D. C. Eastwood, and H. J. Lim Opacification of the Genitourinary Collecting System During MDCT Urography with Enhanced CT Digital Radiography: Nonsaline Versus Saline Bolus Am. J. Roentgenol., January 1, 2006; 186(1): 122 - 129. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J Richenberg and P Thompson Haematuria Imaging, August 1, 2005; 17(1): 34 - 43. [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
