Urinary Tract Infections

Urinary tract infections (UTIs) are caused by bacteria that invade the urinary system and multiply, leading to an infection. UTIs are very common-approximately 8 to 10 million people seek professional medical assistance annually for this disease. Women are affected more than men, although men and children can get UTIs. Approximately one woman in five will have a urinary tract infection in her lifetime.

Most infections are not serious and can be easily treated with antibiotics. However, if left untreated, some infections can result in kidney damage and even death. This is why it is so important to seek appropriate medical treatment if a UTI is suspected.

THE URINARY SYSTEM

The urinary tract is made up of the kidneys, two ureters, the bladder and urethra. The major components are the kidneys, a pair of bean-shaped organs located below the ribs near the middle of one's back. The kidneys comprise a complex filtration system made up of individual nephrons that work together to remove waste products from the blood, which are eliminated from the body in the form of urine. The kidneys also function to maintain a stable balance of salts and other substances in the blood, as well as to produce a hormone erythropoietin, which triggers the production of red blood cells in the bone marrow.

The ureters are tube-like structures that transport the urine from the kidneys to the bladder where the urine is stored. Muscles called sphincters tighten around the urethra to prevent urine from leaking out. There are two sphincters: the internal is not controlled consciously, while the external sphincter is under voluntary control. The bladder is elastic and expands as it fills with urine. When the bladder reaches a certain capacity, which differs for each individual, the brain sends impulses to the internal sphincter to relax and other impulses to a muscle called the detrusor to contract and expel the urine out the urethra. This process is under the voluntary control of the individual, who can hold the urine until social circumstances allow for urination. (Loss of this control is urinary incontinence.)

Urine is normally "sterile," meaning that it usually contains no bacteria. The body accomplishes this through several methods. First, the two sphincter muscles that prevent urine leaking from the bladder to the urethra, also prevent the bacteria that normally colonize the skin from ascending through the meatus (the opening in the urethra) into the bladder. Second, the length of the urethra makes it difficult for bacteria to get to the bladder. The fact that women have a much shorter urethra than men accounts for the five-fold increase of UTIs among women compared to men. Finally, if bacteria do make it to the bladder, the body is equipped with valves where the ureters empty into the bladder, a region known as the trigone. These valves prevent the "reflux" of urine, and any bacteria present, back up into the kidneys. Further, the bladder almost completely empties when urination occurs, so that any bacteria present should be excreted as well. Nevertheless, despite all these defense mechanisms, infections sometimes occur.

RISK FACTORS

There are three types of urinary tract infections:

urethritis is infection of the urethra;
cystitis is infection of the bladder; and
pyelonephritis occurs when bacteria ascend up the ureters and infect the kidneys.

The urinary tract can be infected from above by bacteria that enter the kidney through the bloodstream from an infected source in the body, or a UTI can occur from below by bacteria entering the urethra and spreading upward. Infection from above is most often seen in newborn babies with a systemic infection known as sepsis. Infection from below is much more common. It is most often seen in small children and adults.

Small children, still using diapers, have stool (which is largely bacteria) in close proximity to their urethra. The longer they sit in soiled diapers, the more likely the chance of infection. In addition, small girls are more prone to infection because they have a shorter urethra than boys. Uncircumcised boys are more likely to get an infection than circumcised boys because bacteria survive in warm, moist areas like the area under the foreskin. When toilet trained, older girls may be more likely to get a UTI if they wipe themselves from back to front, because this can expose the vaginal and meatal area to bacteria which colonize the rectum, most commonly Escherichia coli (E. coli). However, infections can be caused by Klebsiella, Proteus, Enterobacter, Pseudomonas, Serratia, Citrobacter, Streptococcus fecalis and, rarely, Staphylococcus aureus.

Sexually active teenagers and adult women are more prone to UTIs because of friction that occurs at the meatus during intercourse, which allows bacteria to enter and ascend the urinary tract. This problem can be avoided by urinating after sexual intercourse.

People with certain medical conditions are more likely to get a UTI than others. Any abnormality in the urinary tract that obstructs the flow of urine, for example a kidney stone, sets the stage for an infection due to urinary stasis. An enlarged prostate (benign prostatic hyperplagia) can also slow the flow of urine and raise the risk of infection.

Another common source of infection is catheters or tubes placed in the bladder. Catheters are normally used when people cannot void, are unconscious or are critically ill, and may stay in place for long periods of time. Some people, especially the elderly or those with nervous system disorders such as spinal cord injury, who lose bladder control may require catheters for the rest of their lives. Bacteria on the outside of the catheter can climb up the device into the bladder and cause infection.

People with diabetes have a higher risk of infection because of changes in the immune system secondary to the high sugar concentrations. Any disorder that affects the immune system raises the risk of developing a UTI. UTIs may occur in infants who are born with abnormalities of the urinary tract, such as posterior urethral valves or vesicoureteral reflux. These conditions sometimes require surgery.

Several studies have shown that women who use a diaphragm are more likely to develop UTIs than women who use other forms of birth control. More recently, investigators have demonstrated that women whose partners use a condom with spermicidal foam also tend to have growth of E. coli bacteria in the vagina.

Many women suffer from frequent UTIs, which is defined as three or more culture-verified UTIs in one year. This condition is known as recurrent cystitis. Studies have shown that nearly 20 percent of women who have one UTI will have another, and 30 percent of those women will have yet another. Of the last group, 80 percent will have a recurrence. Usually the recurrent infection stems from a strain or type of bacteria different from the original UTI, which suggests a separate infection. Research indicates that one factor involved in recurrent UTIs may be the ability of the bacteria to adhere to cells lining the urinary tract. Additional studies have shown that women with specific blood types are more prone to UTIs.

Pregnant women are no more likely to develop a UTI than other women. However, if a UTI occurs it is much more likely to travel to the kidney and cause pyelonephritis. Two to 4 percent of pregnant women develop a UTI; this is believed to be due to the hormonal changes and a shift in the position of the urinary tract during pregnancy. These changes make it easier for bacteria to ascend the urinary tract and travel to the kidneys. For this reason many physicians recommend periodic testing of pregnant women's urine.

SYMPTOMS

Not everyone with a UTI has symptoms, but most people get a least some. These include more frequent urination (the average person urinates six times a day) and dysuria, a painful, burning feeling in the area of the bladder or urethra during urination. Pain at the beginning of urination is usually associated with urethritis, whereas pain in the middle of urination is associated with cystitis.

It is common for a person with a UTI to complain that despite the urge to urinate, only a small amount of urine is passed. It may appear cloudy or even reddish if blood is present. In addition the urine may have a pungent, unpleasant odor. Often women complain of an uncomfortable pressure above the pubic bone and some men experience a feeling of fullness in the rectum.

It also is not unusual to feel bad "all over," with shaky, tired, flu-like symptoms. If a fever is present (greater than 101 degrees Fahrenheit or 39 degrees Celsius) it usually means that the infection has reached the kidneys. Other symptoms specific to kidney infection include pain in the back or side (flank), nausea, and vomiting.

In young children and infants the symptoms of a UTI may be overlooked or mistakenly attributed to another condition. Symptoms in infants and young children include irritability, change in eating habits, unexplained fever that does not go away, urinary incontinence or change in urinary pattern, and loose stools.

DIAGNOSIS

The evaluation of a suspected UTI involves a detailed history, including travel as some parasites can cause UTI symptoms, and physical exam. Your doctor will also want to examine your urine for the presence of white blood cells (pyuria), red blood cells (hematuria) and bacteria (bacteriuria). You will be asked to give a "clean-catch" urine sample, because simply urinating into a sterile cup may not stop contamination by bacteria on the skin (called skin flora). To get a clean-catch sample, you must stop urinating "midstream." After cleaning the meatus and surrounding area with an antiseptic, you urinate a little to expel any bacteria that may be in the urinary tract. You then stop briefly before urinating into the sample cup. The urine is examined under a microscope (urinalysis). If a UTI is suspected, the urine is cultured to see what type of bacteria is growing and which antibiotics will be effective in killing it (called a sensitivity test).

If you have recurrent infections, your urologist may decide to do an imaging procedure of the urinary tract to see if any defects are the cause of the infectionÛkidney stones; diverticula, small pockets that bulge out of the bladder or urethra and contain urine; a narrowing of one of the tubes of the urinary tract; or a cystocele, a condition in women where the structures that support the bladder weaken and allow the bladder to protrude into the vagina. The imaging procedure usually ordered is an intravenous pyelogram (IVP). This test is performed by injecting a special dye. A series of X-rays are taken as the chemical enters the kidneys, ureters and bladder, and finally exits the urethra. If there is an obstruction or abnormality in the urinary tract, it will show up as white on the dark film of these serial X-rays.

Another test that may be performed is called a voiding cystorography (VCUG). It involves instilling a chemical into the bladder and taking serial X-rays as the patient urinates. This test detects any reflux of urine that may be causing UTIs. A renal (kidney) ultrasound may also be ordered to determine if there is any kidney damage due to repeated infections.

When to Call a Healthcare Professional

If symptoms worsen with home therapy or do not improve within 24 hours.
If you have had a UTI that required treatment with antibiotics.

If at any time any of the following apply:

Urologic Conditions