Urinary Tract Infection


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Urinary tract infections are infections that occur in any part of the urinary tract. The urinary tract is composed of the kidneys * bladder * and urethra# The main cause of these infections is bacteria# Sometimes, the infection is carried through the bloodstream to other areas of the body.

What Is Urinary Tract Infection?

When an infection causes inflammation * in the urethra, it is called ure-thritis (yoo-re-THRY-tis). Infections that inflame the bladder are called cystitis (sis-TY-tis). Infections that inflame the kidneys are called pyelonephritis (py-e-lo-ne-FRY-tis).

The primary cause of urinary tract infections is bacteria. Sometimes, the formation of stones or tumors * in the kidneys can cause a blockage in the urinary tract, which puts people at risk of developing a urinary tract infection. Sometimes, other diseases result in urinary tract infection. Urinary tract infection occurs about 10 times more often in women than in men, although infants of both sexes contract the disease at about the same rate.


Urethritis usually is not the result of a urinary tract infection but arises from a sexually transmitted disease such as a chlamydial (kla-MID-ee-al) infection. The main symptom of urethritis is a burning sensation during urination. The condition can be diagnosed with a urine test. Urethritis that is not treated can cause blockage and scarring in the urethra.


When the bladder becomes inflamed from bacteria, a person with cystitis will have a burning sensation during urination. The condition also causes a person to feel the need to pass urine often. Low back pain, mild fever, a tired feeling, and blood in the urine sometimes also are present in cystitis, particularly if the kidneys also are involved.


A urinary tract infection that spreads to the kidneys can be quite serious. The infection needs to be treated properly to avoid any permanent damage to the kidneys. Some symptoms that may be present in kidney infection are back pain, pain in the lower abdomen * , fever, chills, nausea, and vomiting.

How Are Urinary Tract Infections Treated?

First a diagnosis is made, which might be done by procedures that include examining the urine and sending a sample to the laboratory to identify the bacteria. In some cases, doctors use x-ray, ultrasound * , and other methods to diagnose urinary tract disease. Antibiotics * may be prescribed to fight the bacterial infection.

* kidneys (KID-nees) are the pair of organs that filter blood and get rid of waste products and excess water as urine.

* bladder (BLAD-er) is the sac that stores urine produced by the kidneys prior to discharge from the body.

* urethra (yoo-REE-thra) is the tube through which urine is discharged from the bladder to outside of the body.

* bacteria (bak-TEER-ee-a) are single-celled microorganisms, which typically reproduce by cell division. Some, but not all, types of bacteria can cause disease in humans.

* inflammation (in-fla-MAY-shun) is the body's reaction to irritation, infection, or injury that often involves swelling, pain, redness, and warmth.

* tumors (TOO-morz) usually refer to abnormal growths of body tissues that have no physiologic purpose and are not inflammations. Tumors may or may not be cancerous.

* abdomen (AB-do-men), commonly called the belly, is the portion of the body between the chest or thorax (THOR-aks) and the pelvis.

* ultrasound is a painless procedure in which sound waves passing through the body create images on a computer screen.

* antibiotics (an-ty-by-OT-iks) are drugs that kill bacteria.

How Can Urinary Tract Infections Be Prevented?

Practicing good hygiene can help prevent urinary tract infections. It is important to keep the genital, urinary, and anal areas of the body clean. Wiping the rectum separately from the urinary tract opening is important to avoid spreading fecal matter to the urethra, which can cause infection, particularly in females. Urinary tract infections also can be spread through sexual activity; avoiding risky sexual practices will reduce the chances of contracting a urinary tract infection.

See also
Bacterial Infections
Chlamydial Infections
Kidney Disease
Kidney Stones
Sexually Transmitted Diseases
Urethritis, Nonspecific



National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Office of Communications and Public Liaison, NIDDK, NIH, 31 Center Drive, MSC 2560, Bethesda, MD 20892-2560. This organization, part of the National Institutes of Health (NIH), posts fact sheets on urinary tract infections on its website.

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