A UTI is a bacterial infection in some part of your urinary system. Your urinary system includes all the organs involved in making and releasing urine (pee):
- Kidneys – these filter your blood to remove waste and extra water to make urine (pee).
- Ureter – two thin tubes of muscle, one on each side of your bladder, through which urine flows from your kidneys to your bladder.
- Bladder – where you store urine until you need to pee.
- Urethra – when you pee, urine passes along your urethra, a central tube that carries urine out of your body.
When the infection is just in the bladder (cystitis) and urethra (urethritis), it is called a lower UTI. If it travels up to affect one or both kidneys as well (pyelonephritis) then it is called an upper UTI. An upper UTI can be more serious than a lower UTI as the kidneys can become damaged by the infection.
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