Does residual urine predispose to urinary tract infection?

The relationship between the presence of post-micturition residual urine and urinary tract infection is unclear. We have performed a retrospective analysis of 342 studies on bladder emptying and compared the incidence of bacterial infection and pyuria in patients with residual urinary volumes of more or less than 100 ml. In patients with a residual volume > 100 ml 49/219 studies showed evidence of pyuria and 28/198 studies of patients whose residual urine was less than 100 ml showed evidence of infection. In cases where the residuals were > 100 ml 33/123 had evidence of pyuria and 19/109 infection. There was no significant increase in the rate of infection in patients with large residual urinary volumes, suggesting that there is no definite correlation between post-micturition residues and urinary tract infection.