Incidental Bladder Lesions on Prostate Multiparametric MRI: Prevalence and Factors Associated with Bladder Carcinoma

Prostate multiparametric magnetic resonance imaging (MRI) is recommended for prostate cancer detection, staging, and surveillance. Incidental bladder lesions are encountered on these studies but remain under-characterized in the literature. The patient characteristics associated with malignancy for these lesions are not well defined. We evaluated the prevalence, histopathologic outcomes, clinical characteristics, and associations with malignancy for incidental bladder lesions on prostate MRI.

A retrospective review included 31,241 patients undergoing prostate MRI examinations from January 2013 to January 2023. Imaging reports and medical records were analyzed for incidental bladder lesions, demographic data, clinical symptoms, urinalysis findings, and histopathologic outcomes. Lesions were categorized based on biopsy results or negative clinical follow-up for bladder tumors in chart review. Logistic regression analysis and receiver operating characteristic analyses were performed.

Incidental bladder lesions occurred in 0.74% (230/31,241) of examinations, with biopsy-confirmed bladder cancer in 0.11% of patients (34/31,241) or 14.8% (34/230) of cases with lesions. In multivariable analysis, gross hematuria had the strongest association with biopsy-proven bladder cancer (OR 9.26, 95% CI 4.12-20.79, p<0.001). A logistic regression model incorporating age, smoking status, and gross hematuria yielded area under the curve of 0.762 for bladder cancer.

Incidental bladder lesions on prostate MRI may represent opportunities for early detection of bladder cancer, but also have potential for harms related to unnecessary procedures. Considering the presence of gross hematuria, possibly stated as part of the MRI referral or patient questionnaire, could improve risk stratification of encountered bladder lesions and early cancer detection.