Population studies on non-obstructive urinary tract infection in non-pregnant women: importance of method and material. Evaluation of 844 women and 232 male controls.

Abstract

ABSTRACT. In earlier population studies other workers found no significant differences in the blood urea levels between bacteriuric non‐pregnant women and their controls matched for age or for age, civil status, and maternity. From these results, far‐reaching negative conclusions were drawn about the importance of urinary tract infection (UTI) and the value of early diagnosis and screening for bacteriuria. It was also concluded that “asymptomatic bacteriuria” is not truly asymptomatic. From a medical examination, patients with obstructive uropathy, concretions, diabetes mellitus, possible glomerulonephritis, and other parenchymal diseases were excluded from the present study. The investigation comprised 232 male controls and 844 nonpregnant women, aged 21–70 years, who were subjectively asymptomatic at the time of examination. The women were divided into four study series, which were uniform with respect to age and maternity: 1) Controls with no past history of upper or lower UTI and no urinary abnormalities, i.e. neither bacteriuria nor pyuria. 2) Women with a past history of symptomatic UTI but no urinary abnormalities at the time of examination. 3) Women with sterile pyuria. 4) Women with bacteriuria/pyuria. About 40% of the women in the latter two series had no past history of UTI. Thus, “asymptomatic” bacteriuria does exist. The concentrations of serum urea N (SUN) and serum creatinine did not differ significantly between the four series of women. In each series both levels increased similarly with increasing age (“ageing”). There was no significant difference in the women with bacteriuria before and after elimination of the infection by treatment. The levels did not rise with increasing age in the male control series and were significantly higher than in the corresponding female control series. In contrast, the level of maximal urinary concentrating ability was significantly higher in the female series 1 than in series 2. There were no significant differences between women in series 2 and either series 3 or 4. Furthermore, in series 3 and 4 there were no significant differences between women with and without a past history of UTI. Elimination of the bacteriuria was accompanied by improved concentrating ability in series 4. The groups with sterile pyuria and bacteriuria/pyuria, respectively, who had no past history of UTI had significantly lower osmolality than the controls. There was a significant difference in the age‐related reduction of concentrating ability between the control series and the other female series (“ageing”) which showed the greatest decrease. The level was higher in the male than in the female control series, the differences in the regression coefficients being significant and in the intercepts not significant. Consequently, compared with the SUN and serum creatinine concentrations, the maximal concentrating ability seems to be the method of choice in population surveys of this kind. It is essential, however, that the test should be carried out under current standardized conditions. Initial diuresis provoked by oral intake of 20–40 mg of furosemide (Lasix®) followed by fluid deprivation will greatly increase the percentage of technically satisfactory tests. Radiological abnormalities suggestive of “chronic pyelonephritis” were noted at i.v. urography in the same prevalence, 11.0, 8.1 and 9.3%, respectively, in the female series 2, 3, and 4. Thus, contrary to conclusions by others, it cannot possibly be inferred that bacteriuria per se is necessarily related to the appearance of acquired abnormalities of this type, unless it is assumed that the women in series 2 and 3 had antecedent bacteriuria. There was an age‐related continuous increase in such acquired abnormalities in the various female age groups, from 1.2 to 11.8%. Further studies of this kind will be necessary to define any special groups at risk.