IMAGING

doi: 10.1590/S1677-553820100001000019

Bladder tumor staging: comparison of contrast-enhanced and gray-scale ultrasound
Caruso G, Salvaggio G, Campisi A, Melloni D, Midiri M, Bertolotto M, Lagalla R
Dipartimento di Biotecnologie mediche e Medicina legale, Sezione di scienze radiologiche, Università degli Studi di Palermo, Palermo, Italy
AJR Am J Roentgenol. 2010; 194: 151-6

• Objective: The purpose of this study was to evaluate the effectiveness of contrast-enhanced sonography in comparison with conventional sonography in differentiating muscle-infiltrating and superficial neoplasms of the urinary bladder.
  Subjects and Methods: Conventional and contrast-enhanced sonography were performed on 34 consecutively registered patients with bladder tumors. All examinations were reviewed by two independent sonologists. At gray-scale sonography, interruption of the hyperechoic bladder wall was considered the main diagnostic criterion for differentiating superficial and infiltrating tumors. At contrast-enhanced sonography, a tumor was considered superficial when the hypoenhancing muscle layer of the bladder wall was intact; disruption of the muscle layer by enhancing tumor tissue was considered diagnostic of infiltration. A level of confidence in the diagnosis of tumor infiltration of the muscle layer was assigned on a 5-degree scale. Receiver operating characteristic analysis was used to assess overall confidence in the diagnosis of muscle infiltration by tumor at both conventional and contrast-enhanced sonography. Histologic diagnosis was obtained for all patients.
  Results: Final pathologic staging revealed 25 superficial tumors (Ta-T1 disease) and nine muscle-infiltrating tumors (>T1). Conventional sonography depicted five of nine muscle-infiltrating tumors, and contrast-enhanced sonography depicted all nine. The diagnostic performance of contrast-enhanced sonography approached that of the reference standard (area under the receiver operating characteristic curve, 0.996), but the diagnostic performance of gray-scale ultrasound was worse (area under curve, 0.613).
  Conclusion: Our study showed that contrast-enhanced sonography is better than conventional sonography for differentiating muscle-infiltrating and superficial neoplasms of the urinary bladder.

• Editorial Comment
  According to the American College of Radiology Appropriateness Criteria, the use of transabdominal ultrasound for pretreatment staging of invasive bladder cancer receives rating 3 (rating scale 1 = least appropriate and 9 = most appropriate). This poor rating is due to the inherent limitation of the abdominal transducers in the visualization of the layers of the bladder wall, which usually appeared homogeneously hyperechoic. Based on their previous observation that after microbubble administration the layers of the bladder wall were clearly differentiated with conventional ultrasound the authors decided to investigate the effectiveness of contrast-enhanced sonography compared with conventional gray-scale sonography in differentiating muscle-infiltrating and superficial neoplasms of the urinary bladder. The diagnostic performance of contrast-enhanced sonography was much better than the gray scale ultrasound (AUC 0.996 x AUC 0.613). As already mentioned by the authors contrast-enhanced sonography has many of the limitations of other ultrasound techniques (difficulty to detect flat lesions; obesity and calcification impairs bladder wall evaluation; columnar hypertrophy of the bladder wall, calcification and tumor location may be troublesome during examination). However, one of the most important limitations of this technique is that the FDA did not approve yet its use for internal medicine examination. Another important limitation is related to the necessity of specialized contrast-specific ultrasound techniques found only in state-of-the art equipments. With contrast-enhanced ultrasound is also very difficult to obtain information on the extent of extra-vesical spread of large, widely infiltrating tumors and on the status of pelvic lymph node. For this reason, we still prefer to use magnetic resonance imaging as the main imaging modality for local staging of possible invasive bladder cancer (T staging accuracies 73% to 96% of cases and 73% to 98 % accuracy for staging of nodes and metastases).

Dr. Adilson Prando
Head, Department of Radiology and
Diagnostic Imaging, Vera Cruz Hospital
Campinas, São Paulo, Brazil
E-mail: adilson.prando@gmail.com