Chronic urinary tract infection and bladder carcinoma risk: a meta-analysis of case-control and cohort studies.

OBJECTIVE: This meta-analysis of published case-control and cohort studies sought to quantify the magnitude and direction of association between chronic UTI (defined as the infection of the urinary tract that either does not respond to treatment or keeps recurring) and risk of bladder carcinoma (BCa) (i.e., including mainly urothelial carcinoma, squamous cell carcinoma or adenocarcinoma).

METHODS: A literature search was conducted using Medline, Embase, Ovid, Web of Science, Science Direct and Cochrane Library, which was supplemented with manual search of reference lists of the identified articles. Case-control and cohort studies examining UTI as a predictor of BCa risk published through June 2016 were eligible. Using random-effects models, odds ratios (OR) or relative risks (RR) from eligible studies were combined to synthesize summary effect estimates. The included studies were assessed for methodological quality and potential publication bias. Heterogeneity by study characteristics was examined by sub-group and meta-regression analyses.

RESULTS: Eighteen case-control and three cohort studies published between 1963 and 2016 were eligible. Random-effects models showed that UTI was significantly associated with an increased BCa risk both in case-control studies (summary ORRE  = 2.33; 95% CI 1.86, 2.92) and cohort studies (summary RRRE  = 2.88; 95% CI 1.20, 6.89). The observed relationship of UTI with an increased BCa risk was independent of the study characteristics considered. No significant publication bias was detected.

CONCLUSIONS: Chronic UTI was significantly and independently associated with an increased BCa risk. However, due to the presence of high between-study heterogeneity and inconsistent patterns of adjusted confounding effects, more data are needed to clarify the role of chronic UTI in causation of BCa and if established, prompt and effective treatment of UTI may minimize a substantial proportion of BCa risk.