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What is a Urinary Tract Infection (UTI)?

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UTIs are common infections, usually caused by bacteria, in the bladder or urethra.

There are several kinds of UTI. The type of a UTI depends on where the infection occurs. For example:

  • Urethritis is an infection in the urethra.
  • A bladder infection is called cystitis.

If left untreated, a UTI could travel up one or both ureters (pronounced yoo-REE-ters) to the kidney(s), causing pyelonephritis (pronounced pahy-uh-loh-nuh-FRAHY-tis) or a kidney infection. Kidney infections can become serious and may require hospitalization as part of treatment. UTIs are not the only cause of kidney infections.

UTIs are more common among women than among men. They also can affect children. For information about UTIs in children, visit

Last Reviewed: 04/12/2013
Vision National Institutes of Health Home BOND National Institues of Health Home Home Storz Lab: Section on Environmental Gene Regulation Home Machner Lab: Unit on Microbial Pathogenesis Home Division of Intramural Population Health Research Home Bonifacino Lab: Section on Intracellular Protein Trafficking Home Lilly Lab: Section on Gamete Development Home Lippincott-Schwartz Lab: Section on Organelle Biology