Urinary Tract Infection

What is a urinary tract infection (UTI)?

A UTI is an infection in the urinary tract. Infections are caused by microbes—organisms too small to be seen without a microscope. Bacteria are the most common cause of UTIs. Normally, bacteria that enter the urinary tract are quickly removed by the body before they cause symptoms. But sometimes bacteria overcome the body’s natural defenses and cause infection.

What is the urinary tract?

The urinary tract is the body’s drainage system for removing wastes and extra water. The urinary tract includes two kidneys, two ureters, a bladder, and a urethra. The kidneys are a pair of bean-shaped organs, each about the size of a fist. They are located below the ribs, one on each side of the spine, toward the middle of the back. Every minute, your kidneys filter about 3 ounces of blood, removing wastes and extra water. The wastes and extra water make up the 1 to 2 quarts of urine you produce each day. The urine travels from the kidneys down two narrow tubes called the ureters. The urine is then stored in a balloonlike organ called the bladder and emptied through the urethra, a tube at the bottom of the bladder.


What causes UTIs?

Most UTIs are caused by bacteria that live in the bowel. The bacterium Escherichia coli (E. coli)causes most UTIs. The urinary tract has several systems to prevent infection. The points where the ureters attach to the bladder act like one-way valves to prevent urine from backing up toward the kidneys, and urination washes microbes 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, infections still occur.

Who gets UTIs?

People of any age or sex can get UTIs. But about four times as many women get UTIs as men. Women have a shorter urethra, which makes it easier for bacteria to reach the bladder. Also, the opening of a woman’s urethra is near the vagina and anus, where bacteria live. Women who use a diaphragm are also more likely to get UTIs than women who use other forms of birth control.

Others at higher risk for UTIs are people

  • with diabetes or problems with the body’s natural defense system
  • who need a tube to drain their bladder
  • with urinary tract abnormalities that block the flow of urine
  • with spinal cord injuries or other nerve damage

Are UTIs serious?

Most UTIs are not serious, but some infections can lead to serious problems. Chronic kidney infections—infections that recur or last a long time—can cause permanent damage, including kidney scars, poor kidney function, high blood pressure, and other problems. Some acute kidney infections—infections that develop suddenly—can be life threatening, especially if the bacteria enter the bloodstream, a condition called septicemia.

What are the signs and symptoms of a UTI?

You should see your health care provider if you have any of these signs or symptoms:

  • a burning feeling when you urinate
  • frequent or intense urges to urinate, even when you have little urine to pass
  • pain in your back or side below the ribs
  • cloudy, dark, bloody, or foul-smelling urine
  • fever or chills

How are UTIs treated?

UTIs are treated with antibiotics that can kill the bacteria causing the infection. The antibiotic prescribed will depend on the type of bacteria causing your UTI. Some antibiotics may be ruled out if you have allergies to them. Tell your health care provider if you are allergic to any medicines.

You may need to take antibiotics for a few days or for 7 days or longer. The length of treatment depends on a few factors:

  • how severe the infection is
  • whether you were given the right antibiotic at first
  • whether the bacteria resists the antibiotic
  • whether you have repeat infections
  • whether you have a urinary tract abnormality that blocks the flow of urine
  • whether you are male or female; men may need longer treatment because bacteria can hide deep inside prostate tissue

Follow your health care provider’s instructions carefully and completely when taking antibiotics.

Drinking lots of fluids and urinating frequently will speed healing. If needed, you may take various medicines to relieve the pain of a UTI. A heating pad on the back or abdomen may also help.

Will UTIs come back?

For most people, the answer is no. But about one out of every five young women who have a UTI will have another one. Some women have three or more UTIs a year. Men are less likely than women to have a first UTI. But once a man has a UTI, he is likely to have another because bacteria can hide deep inside prostate tissue. Anyone who has diabetes or a problem that makes it hard to urinate may have repeat infections.

If you have repeat infections, your health care provider may refer you to a urologist. Talk with your health care provider or urologist about special treatment plans. For example, you may need to take antibiotics for a longer period of time to help prevent repeat infections. Some patients with frequent UTIs are given a supply of antibiotics to be started at the first sign of infection. Make sure you understand and follow the instructions your health care provider or urologist gives you.

Read the rest of this article and related materials from The National Kidney and Urologic Diseases Information Clearinghouse.

Ilustration of human kidneys and urinary tract

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