Staging of Bladder Carcinoma: MRI—Pathologic Correlation

Abstract

Objective: To evaluate the accuracy of MR imaging in the staging of bladder carcinoma and to correlate the results with pathological stage.Material and methods: Through patients of newly diagnosed bladder carcinoma with a mean age of 45^9.94 years who were candidates for radical cystectomy were included in the study. Patients with distant metastases or those with past history of malignancy elsewhere were excluded. The clinical stage for each patient was determined from the results of the conventional techniques. To avoid artifacts and edema of the bladder wall, cystoscopy and cold cup biopsy / transurethral resection was performed at best 2 -3 weeks before magnetic resonance imaging (MRI). MRI was performed with a 0.2 tesla permanent magnet system (Sigma 0.2T System GEM SO CO1). Within 3 weeks after MRI all patients underwent radical cystectomy. MRI images were prospectively interpreted by two radiologists and reviewed for consensus by one urologist without knowledge of the final pathological findings obtained after surgery. All patients were treated by retrograde radical cystectomy with either ileal conduit or ureterosigmoidostomy or ileal neobladder. Histopathological evaluation included the determination of the type, grade and stage of the tumor. The tumor was staged as per the tumor-node-metastasis (TNM) system (1997). The pathologic findings were finally correlated with the MRI findings.Results: Extension through the deep muscle of the bladder wall was present in 18 of the 20 patients and was diagnosed with a sensitivity of 94.4% and specificity of 100%. Extension to perivesical fat was present in 11 of 20 patients and was diagnosed with a sensitivity of 82% and a specificity of 100%. Invasion of the adjacent organs was present in 3 of 20 patients and was diagnosed with a sensitivity of 33.3% and a specificity of 100%. On the basis of MR findings, the tumor was correctly staged, according to the TNM staging (1997), in 15 of 20 (75%) patients. Tumor extension was overestimated in 2 of 20 (10%) patients and underestimated in 3 of 20 (15%).Conclusion: In summary, MRI is an accurate non-invasive modality for assessing whether the tumor is confined to or extends beyond the bladder wall. It is superior to clinical staging of T 2b , T 3b and T 4 lesions. It is possible to distinguish T 2a from T 2b lesions involving the full thickness of bladder wall and this may have therapeutic implications.