Kidney infection is a serious illness that can start from a simple UTI (Urinary Tract Infection). If a UTI is felt untreated, bacteria may travel from the bladder to one or both kidneys and infect them. When that happens a person experiences fever, chills, nausea, vomiting and back pain and generally feels very ill. Kidney infection is diagnosed by a doctor exam and a urine test. Usually, no other tests are necessary. A kidney infection ...