A urinary tract infection (UTI) is an infection caused by bacteria in part of the urinary tract. In the lower urinary tract, it is simple cystitis (a bladder infection). In the upper urinary tract, it is a kidney infection. Symptoms from a lower urinary tract infection include painful peeing and frequent peeing or wanting to pee (or both). Symptoms of a kidney infection include fever and side and back pain. In old people and young children, the symptoms are not always so clear. The main cause for both types is the bacteria Escherichia coli. Other bacteria, viruses, or fungus may be the cause in rare cases.
Women get urinary tract infections more often than men. Half of women have an infection at some point in their lives. It is common to have repeated infections. Risk factors include sexual intercourse as well as family history. Sometimes a person who had a bladder infection will get a kidney infection. Kidney infection may also, but rarely, be caused by bacteria in the blood. Diagnosis in young healthy women can be based on symptoms alone. Sometimes, the urine needs to be tested. A person with frequent infections can take low-dose antibiotics to prevent future infections.
Antibiotics are used to treat simple cases of urinary tract infections. Resistance to antibiotics is increasing. People who have complicated urinary tract infections sometimes have to take antibiotics for a longer time, or might take antibiotics intravenously (through a vein). If symptoms have not improved in two or three days, the person will need further tests. In women, urinary tract infections are the most common form of bacterial infection. Ten percent of women develop urinary tract infections each year.