Early signs of a kidney infection include back pain, chills, fever, bloody or cloudy urine, and painful, burning urination, reports the Centers for Disease Control and Prevention. Urinating frequently or the urge to do so may accompany these symptoms.
If left untreated, a kidney infection, or pyelonephritis, can cause permanent kidney damage or a life-threatening blood infection, warns Mayo Clinic. The risk for a kidney infection is greatest in women, men with enlarged prostates, and people with kidney stones, weakened immune systems, vesicoureteral reflux or bladder-related nerve damage. Prolonged use of a urinary catheter can also be a contributing factor.