Urinary Tract Infections Overview

A urinary tract infection (UTI) is an infection involving the kidneys, ureters, bladder, or urethra. These are the structures that urine passes through before being eliminated from the body.

• The kidneys are a pair of small organs that lie on either side of the spine at about waist level. They have several important functions in the body, including removing wastes and excess water from the blood and eliminating them as urine.
  
• The ureters, 2 narrow tubes about 6 inches long, drain urine from the kidneys into the bladder.
  
• The bladder is a small saclike organ that collects and stores urine. When the urine reaches a certain level in the bladder, the muscle lining the bladder contracts to expel the urine.
  
• The urethra is a small tube connecting the bladder with the outside of the body. A muscle called the urinary sphincter, located at the junction of the bladder and the urethra, must relax at the same time the bladder contracts to expel urine.

Any part of this system can become infected. As a rule, the higher up the infection, the more serious it is.

• The upper urinary tract is composed of the kidneys and ureters. Infection in the upper urinary tract generally affects the kidneys (pyelonephritis).
  
• The lower urinary tract consists of the bladder and the urethra. Infection in the lower urinary tract can affect the urethra (urethritis) or the bladder (cystitis).

Urinary tract infections are usually referred to as simple or complicated.

• Simple infections occur in healthy urinary tracts and do not spread to other parts of the body. They usually go away readily with treatment.
  
• Complicated infections are caused by anatomic abnormalities, spread to other parts of the body, or are resistant to many antibiotics. They are more difficult to cure.

In the United States, urinary tract infections account for more than 7 million visits to medical offices and hospitals each year.

• Urinary tract infection is much more common in adults than in children, but about 1-2% of children do get urinary tract infections. Urinary tract infections in children are more likely to be serious than those in adults.
  
• Urinary tract infection is the most common urinary tract problem in children besides bed wetting.
  
• Urinary tract infection is second only to respiratory infection as the most common type of infection.
  
• These infections are much more common in girls and women than in boys and men younger than 50 years. The reason for this is not well understood. 
  
• About 40% of women and 12% of men have a urinary tract infection at some time in their life.
  
• Urinary tract infection is less common in men and boys than in women and girls but is more likely to be serious.

Urinary Tract Infection Causes

The urine is normally sterile. An infection occurs when bacteria get into the urine and begin to grow.  The infection usually starts at the opening of the urethra where the urine leaves the body and moves upward into the urinary tract.

• The culprit in at least 90% of uncomplicated infections is Escherichia coli, better know as E coli. These bacteria normally live in the bowel (colon) and around the anus.
  
• These bacteria can move from the area around the anus to the opening of the urethra. The two most common causes of this are poor hygiene and sexual intercourse.
  
• Usually, the act of emptying the bladder (urinating) flushes the bacteria out of the urethra. If there are too many bacteria, this won't stop them.
  
• The bacteria can travel up the urethra to the bladder, where they can grow and cause an infection.
  
• The infection can spread further as the bacteria move up from the bladder via the ureters.
  
• If they reach the kidney, they can cause a kidney infection (pyelonephritis), which can become a very serious condition if not treated promptly.

The following people are at increased risk of urinary tract infection:

• People with conditions that block (obstruct) the urinary tract, such as kidney stones.
  
• People with medical conditions that cause incomplete bladder emptying (for example, spinal cord injury or bladder collapse after menopause.
  
• People with suppressed immune systems: Examples of situations in which the immune system is suppressed are AIDS and diabetes. People who take immunosuppressant medications also are at increased risk.
  
• Women who are sexually active - Sexual intercourse can introduce larger numbers of bacteria into the bladder. Infection is more likely in women who have frequent intercourse. Infection attributed to frequent intercourse is nicknamed "honeymoon cystitis." Urinating after intercourse seems to decrease the likelihood of developing a urinary tract infection.
  
• Women who use a diaphragm for birth control.
  
• Men with an enlarged prostate: Prostatitis or obstruction of the urethra by an enlarged prostate can lead to incomplete bladder emptying, thus increasing the risk of infection. This is most common in older men.
  
• Uncircumcised males - This risk is still relatively low, but it is higher than in circumcised males.
  
• Males are also less likely to develop UTIs because their urethra (tube from the bladder) is longer. There is a drier environment where a man’s urethra meets the outside world, and fluid produced in the prostate can fight bacteria.

The following special groups may be at increased risk of urinary tract infection:

• Very young infants - Bacteria gain entry to the urinary tract via the bloodstream from other sites in the body.
  
• Young children - Young children have trouble wiping themselves and washing their hands well after a bowel movement. Poor hygiene has been linked to an increased frequency of urinary tract infections.
  
• Children of all ages - Urinary tract infection in children can be (but is not always) a sign of an abnormality in the urinary tract, usually a partial blockage. An example is a condition in which urine moves backward from the bladder up the ureters (vesicoureteral reflux).
  
• Hospitalized patients or nursing home residents - Many of these individuals are catheterized for long periods and are thus vulnerable to infection of the urinary tract. Catheterization means that a thin tube (catheter) is placed in the urethra to drain urine from the bladder. This is done for people who have problems urinating or cannot reach a toilet to urinate on their own.

Some women have frequent urinary tract infections. We are not really sure why. This may be an inherited trait, and it may be related to blood type.

Urinary Tract Infection Symptoms

Lower urinary tract infection (cystitis): The lining of the urethra and bladder becomes inflamed and irritated.

• Dysuria - Pain or burning during urination
• Frequency - More frequent urination (or waking up at night to urinate)
• Urgency - The sensation of not being able to hold urine
• Hesitancy - The sensation of not being able to urinate easily or completely (or feeling that you have to urinate but only a few drops of urine come out)
• Cloudy, bad smelling, or bloody urine
• Lower abdominal pain
• Mild fever (less than 101°F), chills, and "just not feeling well" (malaise)

Upper urinary tract infection (pyelonephritis): Symptoms develop rapidly and may or may not include the symptoms for a lower urinary tract infection.

• Fairly high fever (higher than 101°F)
• Shaking chills
• Nausea
• Vomiting
• Flank pain - Pain in your back or side, usually on only one side at about waist level

In newborns, infants, children, and elderly people, the classic symptoms of a urinary tract infection may not be present. Other symptoms may indicate a urinary tract infection.

• Newborns - Fever or hypothermia (low temperature), poor feeding, jaundice
• Infants - Vomiting, diarrhea, fever, poor feeding, not thriving
• Children - Irritability, eating poorly, unexplained fever that doesn't go away, loss of bowel control, loose bowels, change in urination pattern
• Elderly people - Fever or hypothermia, poor appetite, lethargy, change in mental status

Typically, pregnant women do not have unusual or unique symptoms. If you are pregnant, your urine should be checked during prenatal visits because an unrecognized infection can cause pregnancy complications.

Although most people have symptoms with a urinary tract infection, some do not.

The symptoms of urinary tract infection can resemble those of sexually transmitted diseases.

When to Seek Medical Care

Any adult or child who develops any of the symptoms of a urinary tract infection needs evaluation by a medical professional, preferably within 24 hours. Most medical offices can test urine for infection by using a quick urine "dipstick" test.

• If you have symptoms of a lower urinary tract infection, call your health care provider for an appointment, preferably on the very day that symptoms are recognized.
  
• If you have symptoms of an upper urinary tract infection involving the kidneys, call your health care provider immediately. Depending on the situation, he or she will recommend either a visit to the office or to a hospital emergency department.

If you have symptoms of a lower urinary tract infection and any of the following applies to you, you may have a urinary tract infection that involves the kidneys. Go to a hospital emergency department right away.

• Vomiting and inability to keep down clear fluids or medication
• Not better after taking antibiotics for 2 days
• Pregnant
• Having diabetes or another disease that affects the immune system (for example, AIDS)
• Taking medication that suppresses the immune system

Infants, children, and elderly people with any of the signs and symptoms should go to an emergency department for evaluation.