The urinary tract infection (IPA) is a bacterial infection that affects a part of the urinary tract. When it affects the lower urinary tract, the disease is known as common cystitis (inflammation of the bladder), and when it affects the upper urinary tract, the disease is known as pyelonephritis (inflammation of the kidneys). Symptoms of lower urinary tract infection include painful urination and frequent urination or frequent urination (or both) symptoms, whereas symptoms of pyelonephritis include fever and hip pain in addition to lower urinary tract infection symptoms. In older and very young people the symptoms may not be so pronounced or not specific. The underlying cause for both is Escherichia coli, but in rare cases other bacteria, viruses or fungi can also cause it.