RESUMO
OBJECTIVE: For optimum treatment planning and to establish the prognosis, the main objectives of diagnostic imaging techniques after detecting a tumor in the urinary bladder are to determine 1) its nature and histological structure, 2) depth of bladder wall invasion, 3) tumor localization and involvement of the ureter and trigone, 4) involvement of bladder wall lymphatics, and (5) to determine if there is or no regional and/or distant mestatasis. The capabilities of the diagnostic imaging techniques in regard to achieving the foregoing objectives are analyzed. METHODS: This study comprised 160 patients with a suspected or confirmed bladder tumor. The imaging methods utilized were: conventional radiology including IVP, retrograde and double contrast cystography, ultrasound, CT and MRI. RESULTS: Analysis of the images allowed assessment of 18 morphological parameters, of which the following were among the most relevant: presence of ureterohydronephrosis, filling defect(s), tumor localization, tumor base, tumor-mucosa angle, wall stiffness, total wall thickness, changes observed in the perivesical space and degree of pelvic lymph node involvement. Visualization of a bladder filling defect confirms a bladder tumor. The predictors of the biological behaviour of bladder tumors, such as wall stiffness and lumen asymmetry, characteristically express tumor invasiveness. The tumor-mucosa angles in relation to tumor base and peritumoral edema express a higher grade of infiltration for the obtuse angles and a lower grade for the acute angles. Determining tumor stage with accuracy is the essential challenge of the imaging methods in the assessment of bladder cancer. Both CT and MRI are used to analyze four basic aspects prior to treatment: 1) tumor appearance, 2) presence or absence of perivesical invasion, 3) presence or absence of invasion of the adjacent organs, and 4) presence or absence of lymphadenopathies. The accuracy of CT for tumor staging is estimated to be 88%-92% for stage D1 and 80%-85% for stages C and B2, respectively, while MRI has an accuracy of 95% for stage B2 and 85% for tumor stages that compromise adjacent organs such as the prostate, uterus or vagina. CONCLUSIONS: Conventional radiological methods, together with transabdominal or transrectal ultrasound, have a high rate of accuracy for tumor detection. Determination of the stage of tumor invasion requires analysis of wall thickness, width of tumor base, tumor-mucosa angles and perivesical space. CT and MRI provide highly reliable diagnostic information on the foregoing. CT may present some difficulty in determining the stage of bladder wall invasion. With contrast enhancement, MRI has shown a greater capability to differentiate tumor stages B2 and C and is very similar to CT in detecting pelvic or retroperitoneal lymph node involvement.
