Urinary Tract Infection

A urinary tract infection (UTI)can occur anywhere in the urinary tract, including the urethra (urethritis), bladder (cystitis), or kidney (pyelonephritis). Most often, however, UTIs develop in the lower tract as a result of bacteria entering the urethra and moving up the urinary tract system. Unless otherwise noted, it's these lower-tract infections that are addressed below.

Causes of Urinary Tract Infections

Urinary tract infections are one of the most common urological disorders in adults, causing 8.1 million health care visits in the U.S. each year. The bacterium Escherichia coli, which is commonly found in the colon, is a frequent culprit as it's often transferred from the rectal area to the urethral opening.

Other UTI-causing bacteria—such as Staphylococcus, Chlamydia, and Enterococci—are transmitted the same way.

Risk Factors for Urinary Tract Infections

Certain factors make some people more vulnerable to UTIs, including:

  • Gender: Women are more likely to develop urinary tract infections due to their anatomy. (The urethral opening is close to the rectum, which makes bacterial transfer that much easier.)

  • Being sexually active

  • Menopause: During menopause, a woman's estrogen levels decrease, thinning her vaginal walls and modifying the protective layer of the bladder that prevents microbes from attaching to its lining.

  • Diabetes: Diabetes can impact nerves in the bladder, causing it to hold onto urine longer. Stagnant urine provides an environment in which bacteria can grow. Compounding this, the disease also weakens the immune system, making it harder for the body to fight off infection.

  • Enlarged prostate: An enlarged prostate can place pressure on the urethra, which narrows the tube and makes it more difficult for the body to expel urine. Stagnant urine provides an environment in which bacteria can multiply.

  • Pregnancy: Hormonal changes and changes in the structure of the urinary system that occur when a woman is pregnant can increase the risk of UTIs. (Click here for more information on UTIs in pregnancy.)

Symptoms of Urinary Tract Infections

Many people who develop urinary tract infections will not have any symptoms. When symptoms are present, they include the following:

  • Painful urination
  • Burning sensation when urinating
  • Increased urge to urinate
  • Cloudy or foul-smelling urine
  • Blood in the urine (hematuria)
  • Abdominal pain
  • Increased need to urinate
  • Change in urine output (usually a decrease)
  • Pain during intercourse
  • Fever/chills

Even though these symptoms are common for urinary tract infections, they can also indicate other problems with the urinary system. If any of these symptoms develop, contact your physician to determine the cause.

Diagnosis of Urinary Tract Infections

A physician will typically perform a urinalysis to determine if bacteria are present in the urine. If the urine contains bacteria, it may be sent to a lab to determine which bacteria is causing the infection and which medication will be most effective for treating it.

Treating Urinary Tract Infections

Left untreated, UTIs can spread throughout the urinary tract and infect the kidneys and other structures, potentially causing permanent damage. But early intervention with antibiotics can prevent the infection from spreading. When the underlying cause of a UTI is a sexually transmitted infection, both partners will require treatment to prevent further infection and recurrence. (Click here to learn more about treatment for urinary tract infections).


Riley, J. (2012). Urinary tract infection. Conditions and Procedures in Brief, 1-3.

Urinary tract infections in adults. (2012). National Kidney and Urologic Diseases Information Clearinghouse. NIH Publication No. 12–2097.

Have specific questions?

All Article Categories

Suggested Doctors

Sorry, there are no matching doctors in your area
Please choose a different location



See more Suggested Doctors

Recently Asked Questions