Bladder tumor staging: comparison of contrast-enhanced and gray-scale ultrasound

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 perfor- mance 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.