Entrance of Bacteria into the Female Urinary Bladder

Although bladder urine is normally sterile, it seems likely that small numbers of bacteria may enter the bladder commonly in women, especially in association with trauma to the urethra. Our investigation was undertaken to study bladder urine from women without urinary-tract infection and to determine the effect of mild urethral trauma (urethral milking) on isolation of bacteria from bladder urine. Forty suprapubic bladder aspirations were performed in 28 women; bacteria were isolated in low numbers from 10 (25 per cent) of the aspirates. Only one of 16 aspirates before urethral milking was positive, whereas nine of 24 aspirates after milking were positive, often with the same organism as in the external urethra. At urine culture 48 to 72 hours after the aspiration no patient had "significant" bacteriuria (105 or more bacteria per milliliter of urine) with the same organism as isolated from the aspirate. Thus, small numbers of bacteria may enter the urinary bladder in women, especially in association with urethral trauma, without causing urinary infection.