IMAGING

MDCT urography of upper tract urothelial neoplasms
Caoili EM, Cohan RH, Inampudi P, Ellis JH, Shah RB, Faerber GJ, Montie JE
Department of Radiology, University of Michigan Health System, Ann Arbor, MI, USA
AJR Am J Roentgenol. 2005; 184: 1873-81

• Objective: The purpose of our study was to review the MDCT urography appearance of pathologically proven transitional cell carcinomas of the renal collecting system and ureter and to correlate the MDCT urography findings with pathology findings.
• Materials and Methods: Of 370 MDCT urography examinations performed over an 18-month period, 18 patients were diagnosed with 27 renal collecting system or ureteral urothelial neoplasms at endoscopic biopsy (n = 8) or surgery (n = 19). Initial MDCT reports were reviewed to determine the sensitivity of original reviewers in detecting these neoplasms. Two radiologists also retrospectively reviewed these scans and characterized the CT appearance of the neoplasms on both axial CT and 3D reformatted images. Findings at retrospective review were correlated with pathology results to determine whether any CT features could be used to predict tumor grade.
• Results: Eighteen of 27 neoplasms were prospectively identified on MDCT urography, and an additional six neoplasms were detected on retrospective review. Three ureteral neoplasms could not be visualized. The 24 retrospectively detected neoplasms had three distinct MDCT appearances: circumferential urothelial wall thickening (n = 14), small masses (> 5 mm in maximal diameter) (n = 5), and large masses (> 5 mm in maximal diameter) (n = 5). All detected lesions could be seen on axial excretory phase images provided wide window settings were reviewed; however, only six were detected on 3D reconstructions. MDCT urography appearance did not correlate with tumor grade.
• Conclusion: MDCT urography is a promising technique for detecting upper urinary tract neoplasms. The static 3D reconstructions used in this study are insufficient for visualization. Axial image review remains essential for tumor identification.
  
  
• Editorial Comment
  Multidetector CT (MDCT) urography has been shown to be a promising and effective single comprehensive examination in the evaluation of patients with hematuria or with risk for the development of urothelial malignancies. During MDCT urography the images are obtained in the unenhanced phase (detection of calculi), nephrographic-phase (detection of renal masses) and excretory-phase (detection of urothelial lesions).
  The authors nicely presents the imaging findings of 24 neoplasms retrospectively detected in 18 out 370 patients submitted to the “state of the art” MDCT urography. In this investigation 89% of malignant upper tract foci were detectable with this relatively new technique. One of the several important contributions showed by this study was the possibility of detecting small tumors. These small tumors, similarly to larger ones, were both papillary and flat and both high grade and low grade. The authors were able to retrospectively detect small (< 5 mm) tumors. Similarly to larger lesions, these tumors appeared as intraluminal masses and ureteral wall thickening. Most of these small lesions were seen only on the axial images and with wide window settings.
  Our early experience with MDCT has also been rewarding since we have been able to prospectively detect some cases of small urothelial malignancies, two of these confirmed as carcinoma in situ. The use of virtual endoscopy in both of theses cases was useful to confirm the presence of such small lesions and to differentiate them from ectopic or prominent papillae. Additional information was also offered to the surgeon when endoscopic resection was the modality of treatment.
  As pointed out by the authors MDCT will not identify all urothelial tumors due to either its peculiar location or small size or more frequently due to technical problems (lack of opacification of the pelviocalyceal system and ureter).

Dr. Adilson Prando
Chief, Department of Radiology
Vera Cruz Hospital
Campinas, São Paulo, Brazil