Abstract
Bacteria are present throughout the female urethra. The female bladder is thus subject to frequent infection which may result in acute pyelonephritis if reflux is present. The male is protected from bladder infection by his long urethra so that even though reflux is present, his urinary tract usually remains sterile. Absence of symptoms may permit sterile reflux to remain undetected for many years. Patients with sterile reflux show much less evidence of pyelonephritic scarring than do patients with infected reflux. In the sterile cases it seems likely that damage to the kidneys results from the hydrostatic effect of the reflux. While sterile reflux is undoubtedly less serious than infected reflux, it may result in an appreciable amount of damage to the kidneys as demonstrated by the patients in this series.