Urinary Tract Infection

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Urinary tract infection


A urinary tract infection is a bacterial infection that occurs in any part of the urinary tract.


The organs of the body that produce and discharge urine are called the urinary tract. They include the kidneys, ureters, bladder, prostate (in men only), and urethra. Urine contains water and waste products. It is made by the kidneys, and carried through the ureters to the bladder for storage. It leaves the body through the urethra, which carries the urine from the bladder. In men, the urethra travels from the bladder through the prostate and out through the penis. In women, the urethra is shorter than in the male and emerges above the vaginal opening.

Urine is normally sterile, meaning that it is free from infectious organisms such as bacteria. The urinary tract is also built to mechanically resist infections. For example, urine is normally prevented from backing up in the ureters to the kidneys. The flow of urine also flushes out bacteria from the body. However, an infection can occur when bacteria attach to the opening of the urethra and enter the urinary tract, which leads to an inflammatory response of the lining of the urinary tract (urothelium). Infection can affect the urethra (urethritis), the bladder (cystitis ), and if not treated, can even reach the kidneys (pyelonephritis).


According to the National Institute of Diabetes and Digestive and Kidney Diseases (NDDKD), urinary tract infections account for about 8.3 million medical visits each year in the United States. In 2004, these infections required 429,000 hospital stays. Escherichia coli is the main culprit, causing approximately 80% of urinary tract infections in adults.

Urinary tract infection is extremely common in women. It is estimated that at least 33% of all women


  • What causes a urinary tract infection?
  • What are the signs of a urinary tract infection?
  • How is a urinary tract infection treated?
  • Can it be cured?
  • What can I do to prevent a urinary tract infection?
  • Is a urinary tract infection contagious?

in the United States are diagnosed with a urinary tract infection by the time they reach 24 years of age. Many women also suffer from frequent infections: some 20% of women who have had an infection will have a recurrence.

Causes and symptoms

Most urinary tract infections are caused by Escherichia coli bacteria that normally live in the large intestine, and are present in feces. They can enter the urethra from the skin around the anus in the rectal area. Other microorganisms, such as Chlamydia trachomatis and Mycoplasma hominis, often transmitted from one sexual partner to the other, can also cause infections.

A common source of infection are catheters, the tubes that are placed in the urethra or bladder of patients who cannot urinate or are unconscious. Other people suffering from illnesses also require catheters, sometimes permanently, as for example the elderly or patients with nervous system disorders resulting in loss of bladder control. When catheters are not properly cleaned, bacteria can easily be transferred to the urethra or bladder upon insertion.

Common symptoms of urinary tract infection include:

  • a burning sensation or pain when urinating (dysuria)
  • frequent need to urinate
  • need to urinate during the night (nocturia)
  • dark, cloudy urine
  • blood in the urine (hematuria)
  • pus in the urine (pyuria)
  • urge to urinate but only passing small amounts
  • abnormal urine smell


The diagnosis of urinary tract infection is established on the basis of clinical signs and symptoms in combination with urinalysis results. In the urinalysis test, the urine is examined for white and red blood cells and the presence of bacteria (bacteriuria). Cultures may also be obtained to identify the specific organism involved. When an infection does not clear up with treatment, other tests may be performed, such as an intravenous pyelogram, which provides x-ray images of the bladder, kidneys, and ureters.


Urinary tract infections are commonly treated with an antibiotic. Other medications may also be prescribed to relieve the burning and the frequent urge to urinate.

Nutrition/Dietetic concerns

Some studies have shown that women who drink cranberry juice have fewer repeat urinary tract infections. However, more research is required to evaluate the amount required to provide effective protection.


The drugs most often used to treat mild urinary tract infections include trimethoprim (Trimpex), trimethoprim/sulfamethoxazole (Bactrim, Septra, Cotrim), amoxicillin (Amoxil, Trimox, Wymox), nitrofurantoin (Macrodantin, Furadantin), and ampicillin (Omnipen, Polycillin, Principen, Totacillin). Another class of drugs called quinolones include ofloxacin (Floxin), norfloxacin (Noroxin), ciprofloxacin (Cipro), and trovafloxin (Trovan). Longer treatment is often required by patients with infections caused by Chlamydia and Mycoplasma, commonly treated with tetracycline, trimethoprim/sulfamethoxazole (TMP/SMZ), or doxycycline.


Urinary tract infections can often be cured with proper treatment if the infection is not complicated by another condition. Women who have had three infections are likely to continue having them. For instance, once a woman has had one cystitis episode, she has a 20% chance of developing a second infection. After the second infection, she has a 30% risk of developing a third.


Bacterium —A single-celled microorganism that can cause disease. Pl.: bacteria.

Bacteriuria —Presence of bacteria in the urine.

Bladder —Elastic, muscular pouch in which urine collects before being discharged from the body through the urethra.

Catheter —A hollow flexible tube for insertion into a body cavity, duct, or vessel to allow the passage of fluids or distend a passageway.

Cystitis —Inflammation of the bladder.

Feces —Stool, the excrement discharged from the intestines.

Inflammatory response —The immune system's normal response to tissue injury caused by a physical, chemical, or biological substance.

Kidneys —Pair of bean-shaped organs located below the ribs toward the middle of the back that clean the blood, regulate acid concentration and maintain water balance in the body by excreting urine.

Microorganism —An organism that can be seen only through a microscope. They include bacteria, protozoa, algae, and fungi.

Prostate —In males, a walnut-shaped gland that surrounds the urethra at the neck of the bladder. It supplies fluid that goes into semen.

Pyelonephritis —Bacterial infection of the kidney.

Sterile —Free from infectious organisms such as bacteria.

Ureters —Tubes from the kidneys to the bladder that drain urine.

Urethra —The tube leading from the bladder to discharge urine outside the body. In males, the urethra travels through the penis, and in females, it is shorter than in the male and emerges above the vaginal opening.

Urethritis —Infection of the urethra.

Urinary tract —The organs of the body that produce and discharge urine. They include the kidneys, ureters, bladder, and urethra.

Urine —Fluid containing water and waste products. Urine is made by the kidneys, stored in the bladder, and leaves the body through the urethra.

Urothelium —The lining of the urinary tract, including the renal pelvis, ureters, bladder and urethra.

Inflammatory response —The immune system's normal response to tissue injury caused by a physical, chemical, or biological substance.


Urinary tract infections can be prevented with good hygiene, starting with wiping from front to back after using the toilet and keeping the rectal and genital areas clean. Drinking at least six glasses of water every day also maintains the urinary tract in good working order and capable of flushing waste material and bacteria.

Caregiver concerns

Urinary tract infections are common in older community dwellers aged 65 and older, and also in nursing home residents. The challenge involved in diagnosing these infections in this population results from other illnesses that may have symptoms similar to those of urinary tract infection. Some elderly adults who have cognitive impairment are also not able to report their symptoms.



Icon Health Publications. Urinary Tract Infections—A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References. San Diego, CA: Icon Health Publications, 2004.

Kavaler, Elizabeth. A Seat on the Aisle, Please!: The Essential Guide to Urinary Tract Problems in Women. New York, NY: Springer, 2006.

Kilmartin, Angela, and Geoffrey Chamberlain. The Patient's Encyclopaedia of Urinary Tract Infection, Sexual Cystitis and Interstitial Cystitis. Chula Vista, CA: New Century Press, 2004.

Parker, James N., and Philip M. Parker. The Official Patient's Sourcebook on Urinary Tract Infection: A Revised and Updated Directory for the Internet Age. San Diego, CA: Icon Health Publications, 2002.

Stanton, Stuart L., and Peter L. Dwyer. Urinary Tract Infection in the Female. London, UK: Informa Healthcare, 2000.


Hazelett, S. E., et al. “The association between indwelling urinary catheter use in the elderly and urinary tract infection in acute care.” BMC Geriatrics 12 (October 2006): 6–15.

Juthani-Mehta, M. “Asymptomatic bacteriuria and urinary tract infection in older adults.” Clinics in Geriatric Medicine Geriatrics 23, no. 3 (August 2007): 584–594.

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Urinary Tract Infection (UTI). Women's Health.com, Information Page (March 20, 2008) http://womenshealth.gov/faq/Easyread/uti-etr.htm

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American Urological Association (AUA), 1000 Corporate Blvd., Linthicum, MD, 21090, (410)689-3700, (866) 746-4282, (410)689-3800, [email protected], http://www.auanet.org.

National Institute of Diabetes and Digestive and Kidney Diseases, Building 31, Rm 9A06, 31 Center Drive, MSC 2560, Bethesda, MD, 20892-2560, (301)496.3583, http://www2.niddk.nih.gov/.

National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC), 3 Information Way, Bethesda, MD, 20892–3580, (800)891-5390, (703)738-4929, nkudic@ info.niddk.nih.gov, http://kidney.niddk.nih.gov.

Monique Laberge Ph.D.