What Is It?
Pyelonephritis is a kidney infection usually caused by bacteria that have traveled to the kidney from an infection in the bladder.
Women have more bladder infections (also called urinary tract infections) than men because the distance to the bladder from skin, where bacteria normally live, is quite short and direct. However, the infection usually remains in the bladder.
A woman is more likely to develop pyelonephritis when she is pregnant. Pyelonephritis and other forms of urinary tract infection increase the risk of premature delivery.