Pyelonephritis is an inflammation of one or both kidneys. It is thought to be caused by bacteria entering the urinary tract through the urethra. These bacteria may also cause bladder and urinary infections. Pyelonephritis is more commonly found in women, simply because of the physiological construction of the female genito-urinary system. Follow these steps to avoid, spot and treat pyelonephritis to avoid long term damage to your kidneys.