A population-based cohort study examining the association of documented bladder diverticulum and bladder cancer risk in urology patients

OBJECTIVES: Studies have shown a high risk of tumor development within a bladder diverticulum (BD). We were interested in the relationship between BD and the development of bladder cancer. Herein, we attempted to investigate whether there exists an association between documented BD and subsequent risk of bladder cancer. METHODS: We identified 10,662 hospitalized urology patients, including 2,134 documented BD patients (study cohort) and 8,528 non-BD subjects (comparison cohort) from Taiwan’s National Health Insurance database. Only urology patients were enrolled in the study to minimize selection bias. The two cohorts were frequency-matched 1:4 by age, sex and index-year. Patients with less than one year of follow-up were excluded to avoid inverting cause and effect. Risks of developing bladder cancer were estimated using the Cox proportional hazard regression model. RESULTS: There was an increased bladder cancer risk in the documented BD patients. The incidence of bladder cancer in documented BD patients was 2.60-fold higher than that in the comparison group, and the overall risk-factor-adjusted hazard ratio was 2.63 (95% CI, 1.74–3.97). Moreover, stratified analysis by sex also showed that documented BD patients were at higher risk of subsequent bladder cancer than the comparison cohort. The effect of BD on the risk of bladder cancer was higher in males than in females and was more profound in patients without comorbidities than in those with comorbidities. CONCLUSION: In this population-based longitudinal study, urology patients with documented BD might have an elevated risk of subsequent bladder cancer. Based on the limitations of the retrospective study design, further studies are required.