MRI in bladder cancer staging: from principles to practice
Bladder cancer is a common and heterogeneous malignancy in which accurate local staging is critical, as management differs fundamentally between non-muscle-invasive and muscle-invasive disease. While cystoscopy and transurethral resection of bladder tumour (TURBT) remain central to both diagnosis and treatment, they have recognised limitations in assessing depth of invasion, with muscle involvement underestimated in a significant proportion of cases. Multiparametric MRI has therefore emerged as a valuable complementary tool for local staging, particularly in patients with high grade disease or suspected muscle invasion.
This article reviews the principles and practical application of MRI in bladder cancer staging, focusing on technique, interpretation and clinical integration. The Vesical Imaging Reporting and Data System (VI-RADS) is highlighted as a key development that standardises MRI acquisition, reporting and assessment of muscle invasion risk. Optimal patient preparation, appropriate timing of MRI relative to cystoscopy or TURBT and adherence to a VI-RADS-compliant protocol are emphasised as essential for diagnostic accuracy.
The characteristic appearances of bladder cancer on T2-weighted imaging, diffusion-weighted imaging and dynamic contrast-enhanced imaging are described, along with their respective roles within the VI-RADS framework. Key imaging signs, including the ‘inchworm sign’ in papillary tumours and the challenges of tumours arising in bladder diverticula, are discussed. Emerging evidence supporting pre-TURBT MRI pathways, including data from the BladderPath study, suggests that early MRI can expedite correct treatment for muscle-invasive disease while avoiding unnecessary interventions. Overall, MRI is positioned as an increasingly central component of modern bladder cancer staging and management.
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