Urinary tract infection (UTI) is the term for an infection that begins in the kidney, bladder, or urethra.

What is going on in the body?

The kidneys filter and remove waste products and water from the body, and produce urine. Urine travels from the kidneys through two narrow tubes called ureters down to the bladder, where it is stored. When the bladder becomes full, it empties the urine through the urethra to the outside of the body. The urethra is a small tube at the bottom of the bladder. The opening of the urethra is at the tip of the penis in boys and in front of the vagina in girls. The urinary tract is normally free of germs. When bacteria do get in, they can infect and inflame the urethra, bladder, ureters, or kidneys.

What are the causes and risks of the condition?

UTIs are usually caused by bacteria that enter the urinary tract through the urethra and bladder. The bacteria can come from the skin around the genital area and anus. Some children may be prone to UTIs, just as some are prone to colds or ear infections.

Sometimes UTIs are a sign of an abnormality in the urinary tract. Normally, urine flows from the kidneys down the ureters and into the bladder. If the urine flow is blocked, the urinary tract can get infected. This kind of obstruction can be caused by kidney stones or by a narrow urethra or ureters.

UTIs can also occur if the urine flows up the ureters as well as down. This is usually caused by an abnormality in the way the ureters are inserted into the bladder. The condition is called vesicoureteral reflux.

Girls are more likely to get UTIs because they have shorter urethras than boys. Boys that are uncircumcised may also be at risk for UTIs.