Diffusion-weighted magnetic resonance imaging in follow-up of superficial urinary bladder carcinoma after transurethral resection: initial experience

OBJECTIVE To study the feasibility of using diffusion-weighted (DW) magnetic resonance imaging (MRI) in bladder cancer follow-up after transurethral resection (TUR). PATIENTS AND METHODS Included in the study were 47 patients with a history of TUR of superficial bladder carcinoma, who were admitted to our centre between January and December 2011 for follow-up cystoscopy. Before cystoscopy, DW-MRI was performed and the apparent diffusion coefficient (ADC) value was measured in a circular region of interest within the carcinoma and normal bladder wall. Two radiologists, blinded to the results of cystoscopy, independently interpreted the DW images. A comparison of imaging findings with those of cystoscopy was performed using the McNemar test. RESULTS In our 47 patients, cystoscopy identified 34 bladder lesions in 24 patients and in the remaining 23 the bladder looked normal. In the 24 patients with malignant bladders, DW-MRI detected 32/34 tumours with two false-negative findings of lesions in two patients. In 23 patients with non-malignant bladders, the DW-MRI data were accurate for 21 patients, as two patients were misdiagnosed as malignant. The sensitivity, specificity, accuracy, positive and negative predictive values of DW-MRI for identifying bladder tumours were 91.6% (22/24), 91.3% (21/23), 91.5% (43/47), 91.6 (22/24) and 91.3 (21/23), respectively. Using the McNemar test there was no significant difference between DW-MRI and cystoscopy. CONCLUSIONS DW-MRI has a high reliability in differentiating post-TUR inflammatory changes from bladder tumours, which is similar to that of cystoscopy. DW-MRI could be a first-line diagnostic test in follow-up of patients after TUR.