Urethral obstruction may be caused by
prostatic hypertrophy,
urethral stricture, or encrustation of a
urethral-catheter lumen.
Bacteriuria often complicates these obstructions. The sequelae include
fever, acute
pyelonephritis, chronic renal
inflammation, and death. We hypothesized that even brief obstruction of the urinary tract containing a nonvirulent bacterium would result in these complications. Mice challenged transurethrally with Escherichia coli FN414, which is rapidly eliminated from normal mice without causing
bacteriuria,
bacteremia, or renal pathology, were subjected to reversible
urethral obstruction by coating the urethral meatus with
collodion for 1, 3, or 6 h. The majority of mice obstructed for 1 h demonstrated parenchymal renal
inflammation 48 h later. At the end of 3 h of obstruction, 9 of 10 mice were bacteremic; some
bacteremias were present at 48 h after removal of the obstruction. At that time, more severe renal
inflammation was seen in these mice. As little
as 6 h of obstruction resulted not only in the acute changes described above but also in chronic renal
inflammation and
fibrosis in the majority of animals sacrificed 3 and 6 weeks later. Additional studies demonstrated that
urethral obstruction enhanced the uropathogenicity of another nonpathogenic E. coli strain (K-12 strain HB101) and caused more severe renal lesions in mice challenged with E. coli CFT073, isolated from a patient with symptoms of
pyelonephritis. These findings demonstrate that brief
urethral obstruction may (i) induce organisms which are cleared rapidly from the normal urinary tract to cause
bacteriuria,
bacteremia, and
pyelonephritis and (ii) intensify the renal lesions caused by a uropathogen.