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Causes of UTI
In most cases, the causes of a UTI (urinary tract infection) involve a type of bacteria called Escherichia coli (E. coli), which normally lives in the colon. In addition to bacteria, possible causes include other microorganisms (such as chlamydia and mycoplasma). Certain risk factors increase the chances of developing a urinary tract infection. Examples of these risk factors include urinary tract problems (such as kidney stones), medical conditions (such as diabetes), and menopause.
Normally, urine is sterile, meaning it is free of bacteria, viruses, and fungi, but it does contain fluids, salts, and waste products. The urinary system is also structured in a way that helps ward off infection. The ureters and bladder normally prevent urine from backing up toward the kidneys, and the flow of urine from the bladder helps wash bacteria out of the body. In men, the prostate gland produces secretions that slow bacterial growth. In both sexes, immune defenses also prevent infection.
But despite these safeguards, urinary tract infections (UTI) still occur. Tiny organisms such as bacteria cause a UTI. However, other organisms besides bacteria can also be UTI causes.
In most cases, the causes of a UTI involve a type of bacteria, Escherichia coli (E. coli), which normally lives in the colon. In many cases, bacteria first travel to the urethra. When bacteria multiply, a UTI can occur. A UTI that is limited to the urethra is called urethritis. If bacteria move to the bladder and multiply, a bladder infection, called cystitis, results. If the infection is not treated promptly, bacteria may then travel further up the ureters to multiply and infect the kidneys. A kidney infection is called pyelonephritis.
(Click Pyelonephritis for more information on kidney infections.)
Written by/reviewed by: Arthur Schoenstadt, MD
Last reviewed by: Arthur Schoenstadt, MD