MDCT Evaluation of Ureteral Tumors: Advantages of 3D Reconstruction and Volume Visualization

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1 Genitourinary Imaging Review Raman et al. MDCT of Ureteral Tumors Genitourinary Imaging Review Downloaded from by on 02/16/18 from IP address Copyright RRS. For personal use only; all rights reserved Siva P. Raman 1 Karen M. Horton Elliot K. Fishman Raman SP, Horton KM, Fishman EK Keywords: 3D technique, CT urography, MDCT, transitional cell carcinoma, ureter DOI: /JR Received March 5, 2013; accepted after revision pril 29, ll authors: Department of Radiology, Johns Hopkins University, JHOC 3251, 601 N Caroline St, altimore, MD ddress correspondence to S. P. Raman (srsraman3@gmail.com). CME/SM This article is available for CME/SM credit. JR 2013; 201: X/13/ merican Roentgen Ray Society MDCT Evaluation of Ureteral Tumors: dvantages of 3D Reconstruction and Volume Visualization OJECTIVE. This article reviews the use of CT urography in diagnosing ureteral transitional cell carcinomas, different CT urography protocols, CT findings suggestive of ureteral malignancy, and the importance of 3D reconstructions. CONCLUSION. The ureters can be problematic to evaluate on CT, partly because of difficulties in obtaining adequate ureteral distention and opacification. Proper diagnosis hinges not only on appropriate interpretation of the axial images but also on the utilization of a 3D technique (volume rendering or maximum intensity projection) as an ancillary tool. T here is little doubt that CT urography provides results that are equivalent, and almost certainly superior, to those of conventional excretory urography in the evaluation of the upper urinary tracts for transitional cell carcinoma (TCC) [1, 2]. lthough our group has previously described the importance of carefully evaluating the intrarenal collecting systems on CT urography, the evaluation of the ureters is equally vital, given that 5% of all urothelial neoplasms arise from the ureters or renal pelvis [3, 4]. However, evaluation of the ureters using CT can be particularly problematic. Not only are the ureters often poorly opacified and underdistended even when using optimal CT techniques, but the majority of ureteral TCCs also are found in the distal third of the ureters, a segment that is particularly difficult to adequately distend [3]. Moreover, even when well distended, ureteral tumors can be extremely subtle and difficult to detect, particularly when relying primarily on the source axial images. This article will discuss optimizing CT urography techniques to improve ureteral distention, the CT findings that can suggest the presence of a tumor, and the vital role of 3D technique in diagnosing subtle lesions. ackground lthough ureteral TCCs are not nearly as common as TCCs of the bladder, nearly 2290 patients in the United States were diagnosed with ureteral TCCs in 2008, and 700 patients died as a result [5]. Upper tract TCCs can oc- cur in any portion of the ureters or intrarenal collecting systems, but the most common location is thought to be the renal pelvis, accounting for 15% of all renal tumors, likely as a result of the large area of urothelium in this location. Within the ureter itself, TCCs of the distal ureter are much more common (73%) compared with lesions in the mid (24%) and proximal (3%) ureters [5]. lthough TCCs account for 90% of all malignancies in the renal pelvis and ureter, in rare instances, squamous cell carcinomas (10%) and adenocarcinomas (1%) can also present as primary urothelial malignancies [6]. Regardless of their location, TCCs are characterized by their multiplicity (2 5% of upper tract TCCs are bilateral), tendency for metachronous lesions, and their high incidence of recurrence. Most TCCs occur in patients older than 60 years, and men are at greater risk compared with women. Major risk factors include increasing age, male sex, smoking, analgesic overuse (including phenacetin), and a variety of chemical carcinogens (most notably aniline dyes). It is thought that most of the carcinogens that predispose toward TCC are excreted into the urine, where they directly interact with the adjacent urothelium [3, 4]. One relatively unique predisposing risk factor for TCC is alkan nephropathy, an endemic degenerative interstitial nephropathy that confers nearly a 200 times greater risk of TCC (usually low-grade and multifocal TCCs) [5]. lthough urothelial tumors are overwhelmingly the most common neoplasms to involve the ureter, on rare occasions, both lymphoma JR:201, December

2 Raman et al. Downloaded from by on 02/16/18 from IP address Copyright RRS. For personal use only; all rights reserved and metastatic disease can involve the ureter as well. Lymphoma may involve the ureter in up to 6% of cases [7]. However, unlike TCC, lymphomas will tend to infiltrate along the margins of the ureter, rather than truly invading or involving the wall itself, and given the relatively soft nature of these tumors, the degree of proximal urinary tract obstruction is usually considerably less than with TCC (Fig. 1). Metastatic disease to the ureters is quite rare, with the most common primary tumors to metastasize to the ureter being breast cancer, gastrointestinal tract malignancies, prostate cancer, cervical cancer, and renal cell carcinoma [7] (Fig. 2). From an imaging perspective alone, distinguishing a metastasis from TCC may not be possible without taking into account the patient s history of a primary malignancy elsewhere in the body. lthough the ureters must be looked on with suspicion in any patient who presents for a CT examination with either gross or microscopic hematuria, the pretest probability increases markedly in patients with a known bladder TCC: 2 4% of patients with bladder TCCs ultimately develop an upper tract TCC, making it vital that this subgroup of patients undergoes CT urography not only at initial presentation but also during routine followup [5]. Gross or microscopic hematuria is the most common presenting symptom in patients with urothelial malignancies of the renal pelvis or ureter and is present in over 75% of patients. s a result, any patient who presents with hematuria should undergo imaging of their upper tracts (typically with CT urography), as well as evaluation of the bladder with conventional cystoscopy (particularly in patients older than 40 years) [1, 8]. Fig year-old man with diffuse large cell lymphoma and involvement of right renal pelvis and ureter. C, Coronal () and axial ( and C) contrast-enhanced images show diffuse masslike thickening (arrows) of ureter and renal pelvis. However, despite this, there is little proximal pelvocaliectasis. CT Technique Starting in the late 1990s, it became clear that excretory phase imaging during contrast-enhanced CT allowed adequate opacification of the upper urinary tracts that was at least comparable (and almost certainly superior) to results provided by conventional excretory urography [1, 2, 9, 10]. Since that time, a variety of different CT urography protocols have been used, which can be broadly divided into three categories: singlebolus technique, split-bolus technique, and, less commonly, triple-bolus technique. Single-olus Technique The single-bolus technique is the earliest of these three CT urography protocols and Fig. 2 Two patients with metastatic disease to ureters., 55-year-old woman with metastatic colon cancer to left ureter. In addition to extensive retroperitoneal adenopathy, there is soft-tissue mass (arrow) obstructing left ureter., 78-year-old man with metastatic prostate cancer to right ureter. Soft-tissue nodule (arrow) is obstructing ureter. is still the most commonly used in day-today practice. In this technique, a single fullstrength bolus of contrast agent is administered, followed by the acquisition of arterial or venous phase images and, subsequently, delayed excretory phase images [4]. Given that the entirety of the dose contributes toward the excretory phase images, this technique provides optimal opacification and distention of the collecting system and ureters. Moreover, by acquiring multiple different phases (often arterial, venous, and delayed), this technique has greater sensitivity for small renal cell carcinomas (compared with split-bolus and triple-bolus techniques), another major cause of hematuria. However, as a result of the need for multiple different im- C 1240 JR:201, December 2013

3 MDCT of Ureteral Tumors Downloaded from by on 02/16/18 from IP address Copyright RRS. For personal use only; all rights reserved aging phases, this protocol is associated with the greatest radiation dose to the patient. Split-olus Technique The split-bolus technique entails dividing the total contrast agent dose into two and acquiring images with a combined excretory and nephrographic phase. In an example protocol, 50 ml of contrast agent could be injected initially, followed by the injection of a second 80-mL bolus 5 minutes later and, finally, by the acquisition of a single set of contrast-enhanced images at 7 minutes with enhancement of the renal parenchyma in the nephrographic phase and opacification of the collecting system in the excretory phase. The main advantage of such a protocol is reduced radiation dose, because the number of imaging phases is minimized [11, 12]. Nevertheless, there is little doubt that this technique provides less-robust opacification of the collecting system, because only one half of the contrast agent dose contributes to the excreted contrast agent, and, in particular, opacification of the distal ureters appears to be a consistent problem [11, 12]. Triple-olus Technique The triple-bolus technique, which is conceptually similar to the split-bolus technique, involves splitting a full dose of contrast agent into three discrete boluses, allowing the acquisition of a combined corticomedullarynephrographic-excretory phase. In a study by Kekelidze et al. [13], 30 ml of contrast agent was initially administered, followed by 50 ml at 435 seconds and 65 ml at 488 seconds, with the patient finally scanned at 510 seconds. s with the split-bolus technique, this protocol, in theory, reduces the patient s contrast agent dose but likely at the expense of distention and opacification of the collecting systems and ureters [13]. Furthermore, by reducing the number of phases acquired in both split-bolus and triple-bolus protocols, the sensitivity for small renal cell carcinomas undoubtedly decreases, because small lesions may only be seen conspicuously in one particular phase of enhancement. When designing a CT urography protocol, the decision must also be made as to whether to use a number of ancillary techniques described in the literature, including abdominal compression, IV saline, IV furosemide, and prone positioning [4]. lthough there are arguments in favor of each of these techniques, the data are equivocal regarding their impact on collecting system and ureteral distention. Fig year-old man with ureteral pseudolesion (arrow) on coronal maximum-intensity-projection image secondary to crossing vessel. bdominal compression, which is often performed using inflatable compression balloons positioned across the patient s abdomen, can be cumbersome to use, especially for obese patients, and may be contraindicated for patients with abdominal aortic abnormalities or recent surgery. Moreover, the efficacy of compression is questionable, with a study by Caoili et al. [14] suggesting no real benefit in terms of collecting system distention. Furthermore, this technique, which is primarily designed to improve distention of the proximal urinary tract, may necessitate a separate set of images following the release of compression to fully visualize the lower urinary tract or distal ureters [14]. Similarly, Fig year-old woman with hematuria. Coronal contrast-enhanced multiplanar reformation shows subtle urothelial thickening (arrow) in left mid ureter, finding that was ultimately found to represent ureteral transitional cell carcinoma. Fig year-old woman with right ureteral transitional cell carcinoma., Coronal maximum-intensity-projection image shows medium-length stricture (arrow) of right proximal ureter., Closer examination of coronal multiplanar reformatted image in excretory phase shows focal soft-tissue thickening (arrow) in this same location. although some studies have suggested that IV hydration may be beneficial in terms of distention, not all studies have concurred, and oral hydration may ultimately produce equivalent results [14 17]. IV diuretic administration (usually furosemide) likely improves collecting system distention and opacification, as shown by Silverman et al. [18]. However, the practical difficulties in administering diuretics routinely, as well as the need to take into account medication allergies and hypotension, make this a difficult element to incorporate for some practices. Overall, given that the data in the literature are mixed regarding the efficacy of many of these practices, as well as the practical difficulties of JR:201, December

4 Raman et al. Downloaded from by on 02/16/18 from IP address Copyright RRS. For personal use only; all rights reserved implementing them into routine day-to-day practice, our practice now uses only oral hydration as an ancillary technique. t our institution, we have chosen to use the single-bolus technique, with 100 ml of nonionic IV contrast agent (iohexol [Omnipaque 350] or iodixanol [Visipaque 320], GE Healthcare) administered at the beginning of the study. In our opinion, although there may be a radiation dose penalty as a result of performing multiple phases, we think that this technique provides the best chance of obtaining adequate ureteral distention and opacification, as well as optimizing lesion detection and characterization [4]. Given the intense concentration of contrast agent in the Fig year-old woman with transitional cell carcinoma of left proximal ureter. C, Coronal maximum-intensity-projection image in excretory phase () shows focal narrowing (arrow, ) of left proximal ureter, corresponding to segment of urothelial thickening and hyperenhancement (arrows, and C) on coronal arterial phase () and excretory phase (C) images. Fig year-old woman with transitional cell carcinoma of left proximal ureter (upper pole moiety in duplicated collecting system)., Coronal maximum-intensity-projection image in excretory phase shows narrowing (arrow) of proximal ureter., Reappraisal of coronal multiplanar reformatted image in excretory phase shows subtle ureteral wall thickening (arrow). Fig year-old woman with transitional cell carcinoma of right intrarenal collecting system and renal pelvis. Coronal maximum-intensity-projection image in excretory phase shows stricture (arrow) of proximal ureter and renal pelvis. This was found to correspond to subtle infiltrative wall thickening in this same location on axial images (not shown). collecting system (particularly with the single-bolus technique) on the delayed excretory phase images, beam-hardening artifact from the excreted contrast agent can be a problem, potentially obscuring lesions in the intrarenal collecting system and pelvis. s a result, in most cases, we think it is generally not advisable to acquire delayed images any later than 5 minutes after contrast agent injection [19]. s an exception, however, if we observe severe collecting system obstruction on the arterial and venous phase images, we will typically acquire the delayed images at 8 minutes (instead of 5 minutes), in hopes of improving the chances of acquiring images with excreted contrast agent. In a few cases, by acquiring images at 5 minutes, the ureters may not yet be entirely opacified, and even opacified segments may not be fully distended. In such select situations, it is imperative that the images be evaluated at the time of acquisition and that an additional delayed scan at 8 10 minutes be performed to ensure adequate ureteral evaluation [20]. We do not routinely use abdominal compression, diuretics, IV saline, or prone positioning in our practice, because we think that simply giving the patient oral hydration provides equivalent results [16]. 3D Technique t our institution, all CT urography datasets are evaluated twice as a result of our de- C 1242 JR:201, December 2013

5 MDCT of Ureteral Tumors Fig year-old man with transitional cell carcinoma of left proximal ureter and renal pelvis. C, Coronal volume-rendered image in excretory phase () shows stricture (arrow, ) in left renal pelvis and ureter, corresponding to urothelial thickening and periureteral fat stranding (arrows, and C) on coronal arterial phase () and excretory phase (C) images. Downloaded from by on 02/16/18 from IP address Copyright RRS. For personal use only; all rights reserved Fig year-old woman with unexplained hematuria for several months and prior negative CT urogram., fter source axial images were initially thought to be normal, 3D evaluation by second reader revealed subtle irregularity (arrow) of left mid ureter on coronal volume-rendered image in excretory phase., Closer examination of coronal multiplanar reformatted image in excretory phase shows subtle urothelial thickening (arrow) in this location, which was later discovered to represent ureteral transitional cell carcinoma. Fig year-old woman with severe bilateral urinary tract infection. and, xial () and coronal () images in arterial phase show bilateral intense urothelial enhancement (arrows) in ureters and proximal collecting systems, with periureteral fat stranding and induration. Patient s urinalysis was floridly positive for infection, and no evidence of underlying malignancy was identified. C partment s workflow requirements. The first evaluation involves a dedicated examination of the source axial images, which are initially acquired at 0.75 mm and reconstructed to 3 mm for review by the radiologist. t this time, coronal and sagittal reconstructions (3 mm) created directly at the scanner are also evaluated. This initial survey of the source axial dataset is followed by a second 3D evaluation (usually by a separate second reader) at a stand-alone workstation (syngo MultiModality Workplace, Siemens Healthcare) with dedicated postprocessing software (InSpace, Siemens Healthcare). Two 3D reconstructions are interactively created by the interpreting radi- JR:201, December

6 Raman et al. Downloaded from by on 02/16/18 from IP address Copyright RRS. For personal use only; all rights reserved ologist: maximum-intensity-projection (MIP) images and volume-rendered (VR) images. MIP MIP algorithms select the highest-attenuation voxels along lines projected through the volumetric dataset and then project these highattenuation voxels into a 2D image. lthough MIP images have traditionally been considered to be most useful in the evaluation of vasculature (particularly in CT angiography), we have found them to be extraordinarily helpful in evaluating the ureters (particularly when well opacified in the delayed excretory phase). However, one should note that this reconstruction algorithm does suffer from some weaknesses, including the fact that portions of the ureters can be obscured by other higher-attenuation adjacent structures (such as calcifications and vasculature) (Fig. 3). Second, although it is a 3D technique, MIP images are 2D representations of the source data, and the 3D relationship between different structures will not be perceptible [21]. VR The VR technique involves classifying the amount of specific tissue types found in each voxel of a dataset and then subsequently assigning a color and transparency according to the percentage of each tissue type in that voxel. Once color and transparency have been assigned to each voxel on the basis of the user s input, the rendering software casts simulated rays of light through the voxels in the volumetric dataset, which are modulated by the color and transparency of each voxel. The VR technique uses a more-complex computer algorithm, compared with MIP imaging, and is relatively computationally intensive [21]. One particularly useful application of VR imaging in the genitourinary system is the creation of a translucent shaded surface display that allows virtual endoscopic images of the collecting systems and ureters [21 24]. Image Interpretation and Diagnosis When evaluating both the source axial dataset and 3D reconstructions, several key imaging features can strongly suggest the presence of malignancy. Fig year-old man with right ureteral transitional cell carcinoma., Coronal maximum-intensity-projection image in excretory phase shows diffuse attenuation and narrowing of right ureter, with severe pelvocaliectasis., Coronal arterial phase reveals intense urothelial enhancement in ureteral wall (arrow) with multiple small tumor vessels and neovascularity. Fig year-old man with diffuse transitional cell carcinoma of left renal pelvis and ureter. and, Coronal arterial phase () and excretory phase () images show diffuse thickening of left renal pelvis and ureter (arrows), with periureteral fat stranding. This was originally thought most likely to represent infection but was ultimately found to be transitional cell carcinoma. Urothelial Thickening Urothelial thickening is the most common manifestation of TCC, accounting for 14 of 24 (58%) of lesions in a series by Caoili et al. [25] (Figs. 4 10). In particular, a series by Xu et al. [26] suggested that urothelial thickening in the renal pelvis is extremely predictive of malignancy (88%), whereas thickening in the ureter itself is less predictive in the absence of other ancillary findings (33%). Nevertheless, the association between urothelial thickening and malignancy stresses the importance of using all the acquired phases of contrast, because subtle urothelial thickening should be visible not only on the excretory phase images but also on the corticomedullary or nephrographic phases. Moreover, if the ureters are extremely well distended with contrast agent, beam-hardening artifact may make subtle urothelial thickening more apparent on the arterial or venous phase images. Even in cases where ureteral wall thickening is circumferential and smooth, rather than irregular and eccentric, it must still be looked on with suspicion [3]. Urothelial Enhancement TCC will often show early enhancement on the arterial phase images, making the inclusion of an arterial phase into protocols extremely useful [3] (Figs. 6, 11, and 12). Increased urothelial enhancement, particularly when focal or asymmetric, should at least raise suspicion as to the presence of malignancy. In rare cases, true neovascularity and tumor vessels related to a TCC can be seen on the arterial phase images in association with a site of urothelial thickening, strongly suggesting the presence of malig JR:201, December 2013

7 MDCT of Ureteral Tumors Downloaded from by on 02/16/18 from IP address Copyright RRS. For personal use only; all rights reserved nancy (Fig. 12). Notably, however, urothelial enhancement (and thickening) can also be inflammatory in nature, related to infections, chronic inflammatory conditions, or instrumentation (such as stents) [7] (Fig. 11). Ureteral Calcifications In a patient with hematuria, the presence of a calcification in the ureter should not always automatically be assumed to be a ureteral calculus. lthough this might be an appropriate assumption when the calcification is in the center of the ureteral lumen, eccentric calcifications or calcifications that appear to be within the wall of the ureter itself should raise suspicion as to the presence of underlying malignancy [5]. Periureteral Fat Stranding Fat stranding around the ureter has traditionally been associated with infectious ureteritis and urinary tract infections. However, periureteral fat stranding, particularly in conjunction with irregular ureteral wall thickening and other ancillary signs of malignancy, can represent extramural spread of tumor (Figs. 9 and 13). Particularly in cases where periureteral fat stranding does not resolve on sequential examinations despite treatment, the possibility of TCC must be considered [3]. Filling Defect or Mass Endoluminal filling defects, whether small or large, should raise concern for malignancy (Figs. 14 and 15). However, the positive predictive value of a filling defect (for malignancy) is greater in the ureter (87.5%) than in the pelvicalyceal system (50%) [26]. Small lesions measuring less than 5 mm can be very difficult to detect prospectively, particularly in the excretory phase where beam-hardening artifact from the contrast agent can obscure small lesions. In such cases, using wide window settings, rather than the standard soft-tissue window, is essential, and some of these smaller lesions may actually be easier to visualize on arterial or venous phase images, particularly if they are avidly enhancing [25]. In addition, readers should be aware that small lesions or filling defects can be obscured when viewing the excretory phase images using MIP reconstruction, because only the highest-attenuation voxels, rather than the low-attenuation tumor, will be displayed. Hydronephrosis and Hydroureter Even in cases where a discrete lesion is not readily visible to the reader, the two ureters must be assessed in tandem for subtle differences or asymmetry in ureteral caliber (Figs. 12 and 16). Even subtle dilatation of one ureter should not merely be attributed to peristalsis, but the ureter should then be carefully evaluated for a transition point or abrupt change in caliber that may hint at the presence of an obstructing lesion. In most cases, TCCs that present as a stricture will be associated with soft-tissue thickening, but this may not always be the case, and any suspected stricture must be further evaluated with ureteroscopy [3]. Fig year-old woman with transitional cell carcinoma of right distal ureter. and, Initially missed on source axial image (), focal irregular filling defect (arrow, ) in right distal ureter (with mild proximal hydroureter and pelvocaliectasis) was identified on coronal volume-rendered image (arrow, ). Fig year-old man with left ureteral transitional cell carcinoma. and, Coronal maximum-intensity-projection image in excretory phase () nicely shows irregular filling defect (arrow, ) in left distal ureter, corresponding to subtle filling defect (arrow, ) in source axial image (). This lesion was initially missed on review of axial images but was identified by second reader on 3D image. enefits of 3D Imaging In a study by Caoili et al. in 2005 [25], using 4- and 8-MDCT, the use of VR and MIP 3D imaging techniques allowed the visualization of six TCCs that were otherwise not detected. Today, although there have been few new data in the literature regarding the utility of 3D techniques in CT urography, we have found that the benefits of 3D imaging and CT urography are even more profound given the improved temporal and spatial resolutions of the latest scanners and the ability to acquire isotropic datasets with identical resolutions in all three planes. t our institution, where two separate readers interpret the axial and 3D datasets, we have seen numerous TCCs initially missed (including several of the examples presented in this review) on a review of the axial images and multiplanar reformations but subsequently diagnosed on the 3D images. In our experience, on the ba- JR:201, December

8 Raman et al. Downloaded from by on 02/16/18 from IP address Copyright RRS. For personal use only; all rights reserved sis of the use of 3D imaging in all of our CT urography studies over the last several years, 3D imaging offers several tangible benefits, as outlined in the following subsections. ccentuation of Subtle Strictures and Sites of Narrowing Subtle differences in caliber between the two ureters are often not perceptible on the source axial images, and the inability to visualize the ureters in their entirety on the coronal multiplanar reformations also makes it difficult to appreciate caliber differences. Coronal MIP and VR images can nicely delineate the entirety of both ureters in a single imaging plane, making it much easier to detect subtle sites of narrowing and proximal dilatation. Even in cases where this may merely reflect ureteral peristalsis or incomplete filling or distention, the coronal VR and MIP images can be cross-referenced with the source axial images for signs of subtle wall thickening or abnormal enhancement. Fig year-old man with ureteral transitional cell carcinoma. and, Coronal multiplanar reformatted () and coronal volume-rendered () images show dilatation of proximal and mid right ureter with abrupt change in caliber and focal thickening (arrows), appearance known as goblet sign. bnormal Urothelial Enhancement and Thickening The VR technique, in particular, can accentuate subtle differences in wall thickness and urothelial enhancement. When a 3D technique is used, it should not be used merely in conjunction with the excretory phase images but should be used with all acquired imaging phases. s mentioned already, the arterial phase may be the phase in which subtle wall thickening and urothelial hyperenhancement are best appreciated. Moreover, we have found that VR images are particularly useful in cases where there is subtle wall thickening only involving a small portion of the ureteral circumference, especially when such thickening extends over only a short distance in the craniocaudal dimension, because this type of abnormality is extremely easy to miss on axial image review. Evaluation of the Distal Ureters The distal ureters are, by far, the most difficult location in the collecting systems to evaluate in either the axial or coronal planes, and distinguishing a true stricture or urothelial thickening from physiologic peristalsis can be challenging. We have found 3D imaging to be useful in delineating true strictures or tumors in this location: Rather than simply seeing an area of narrowing at the ureterovesical junction (as on the axial images), 3D images can help illustrate abrupt or irregular margins of the narrowing, which can suggest a tumor, rather than physiologic ureterovesical junction narrowing or poor distention. Flat Polyploid Lesions lthough large nodules and masses are not difficult to identify on the source axial images alone, subtle flat polyploid lesions can be increased in conspicuity with VR or MIP techniques. Conclusion The ureters can be difficult to evaluate well using CT urography, and even studies performed using optimal techniques and up-todate protocols can be limited by inadequate ureteral distention and opacification. However, even in cases where the ureters are well distended, many cases of ureteral TCC can be extraordinarily subtle and difficult to detect. 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