Infection (usually bacterial) and inflammation of kidney tissue and the renal pelvis. Acute pyelonephritis is usually localized and may have no apparent cause. Symptoms include fever, chills, lower-back pain, and bacteria and white blood cells in the urine. Treatment with antibiotics requires one to three weeks. Scar tissue forms, but kidney function is usually not impaired. Chronic pyelonephritis results from repeated bacterial infections, which may have no symptoms but destroy more and more tissue over years. If it is diagnosed before too much function is lost, surgery may help, but uremia, severe infections, and heart and blood-vessel disorders can lead to death. Dialysis or kidney transplant sometimes prolongs life.