Role of Diffusion -Weighted MRI in Evaluation of Urinary Bladder Masses

Urinary bladder cancer is a common malignant tumor of the urinary tract in both men and women. Proper management of the urinary bladder cancer depends on the stage of the lesions. Differentiating the histopathological types, tumor grade and the depth of tumor invasion are very important for determining the therapeutic approach and are highly correlated with the recurrence, progression and patient's survival. Radical cystectomy (RC) and lymphadenectomy after neoadjuvant chemotherapy is the standard treatment for muscle invasive tumors, whereas the treatment of choice for non-muscle invasive tumors is transurethral resection (TUR) ±chemo/immunotherapy. Cystoscopy with biopsy is still the best tool for bladder cancer staging due to its high sensitivity in detecting lesions and the possibilities of tumor resections, but the main drawbacks are invasiveness, limitation in detection of flat lesions, and lack of the assessment of extra-vesical tumor invasion. Modern diagnostic modalities circumvent these limitations like blue-light cystoscopic examination and infrared cystoscopy. For the radiological evaluation of the urinary bladder, magnetic resonance imaging (MRI) is a valuable imaging modality due to high tissue contrast and multiplanar imaging capabilities. Diffusion-weighted images provides useful information for evaluation of local T stage of the urinary bladder cancer, specially in differentiating T1 stage or lower tumors from T2 stage and higher tumor stages. Apparent diffusion coefficient (ADC) delineating the degree of water molecular diffusion and the degree of restriction to water diffusion in biological tissues is inversely correlated to the integrity of the cell membranes and the tissue cellularity. The apparent diffusion coefficient (ADC) value has been revealed as quantitative measure of the degree of malignancy of the lesions. Decreased ADC values were reported with malignant lesions which have a larger cell diameter and more cellularity than normal