Intermittent catheterization and vesical defenses.

The effectiveness of intermittent catheterization in eradicating bacteriuria in patients requiring catheterization for inadequate voiding was subjected to a mathematical analysis to establish its theoretical basis. It can be shown that, at 1 extreme, with 6 ml. urine remaining in the bladder, assuming reasonable hydration, catheterization must be done at least every 2 to 2 1/2 hours to limit bacteriuria. In contrast, if as little as 0.5 ml. urine is left behind, catheterization may be done every 4 to 5 hours to achieve the same result. Moreover, from the graphic depiction of the calculation it is seen that a reduction in the intervals between catheterization has a much greater effect than an increase in the urinary output in the reduction of the bacterial count. The volume of residual urine after catheterization was directly determined by measurement of phenolsulfonphthalein that was washed out after drainage by catheter in the female dog and in women. In the dog it averaged 0.435 ml. but in women it was somewhat greater than that after normal voiding. Upon applying the equation relating frequency of catheterization and urinary output to residual urine in a clinical program of intermittent catheterization, we found that the usual (convenient) schedule often resulted in showing that an unattainably small volume of urine would have to be left in the bladder. Actual measurement of residual urine by the modified phenolsulfonphthalein test provides the data needed to design a program of intermittent catheterization for each patient that will lead to urinary sterility.