Kidney infections may develop as a complication of a bladder infection or due to a disorder that is specific to the kidney such as a stone or abnormal structure. Typically only one of the two kidneys is affected by the infection, and women are more prone to the condition than men. Usual symptoms of a kidney infection include flank pain, fever, nausea, diarrhea, blood in the urine, painful urination and urinary urgency. In most cases, a kidney infection can be quickly and effectively treated with antibiotic and pain medications along with fluids to re-hydrate the patient. In severe cases, hospitalization may be required so that intravenous antibiotics can be administered.