Chronic pyelonephritis is a sudden and severe kidney infection that causes the kidneys to swell, according to Healthline. The condition can cause permanent damage to the kidneys.
Pyelonephritis infections usually originate in the lower urinary tract, with bacteria entering the body through the urethra, then multiplying and spreading to the bladder before traveling through the ureters to the kidneys, explains Healthline. Symptoms typically appear within two days of infection and may include abdominal, back, side or groin pain; high fever; painful or burning urination; cloudy, bloody or fishy-smelling urine; or urgent or frequent urination.
Home treatment with antibiotics resolves most cases of pyelonephritis, but severe infections sometimes require intravenous antibiotic therapy in a hospital, states WebMD.