A urinary tract infection (UTI) is an infection from microbes. These are organisms that are too small to be seen without a microscope. Most UTIs are caused by bacteria, but some are caused by fungi and in rare cases by viruses. UTIs are among the most common infections in humans.
A UTI can happen anywhere in your urinary tract. Your urinary tract is made up of your kidneys, ureters, bladder, and urethra. Most UTIs only involve the urethra and bladder, in the lower tract. However, UTIs can involve the ureters and kidneys, in the upper tract. Although upper tract UTIs are more rare than lower tract UTIs, they’re also usually more severe.
Symptoms of a UTI depend on what part of the urinary tract is infected.
Lower tract UTIs affect the urethra and bladder. Symptoms of a lower tract UTI include:
burning with urination
increased frequency of urination without passing much urine
increased urgency of urination
urine that looks like cola or tea
urine that has a strong odor
pelvic pain in women
rectal pain in men
Upper tract UTIs affect the kidneys. These can be potentially life threatening if bacteria move from the infected kidney into the blood. This condition, called urosepsis, can cause dangerously low blood pressure, shock, and death.
Symptoms of an upper tract UTI include:
pain and tenderness in the upper back and sides