The urinary tract consists of the kidneys, ureters (which connect the kidneys and the bladder), bladder, and urethra. Urinary tract infections (UTIs) can occur in any part of the urinary tract. Most UTIs are caused by bacteria. They can also be caused by fungi or viruses.
UTIs are the second most common type of infection in humans. The National Kidney & Urologic Diseases Information Clearinghouse (NKUDIC) reports that UTIs account for over eight million doctor visits annually.
What Is the Urinary Tract?
Your kidneys are two bean-shaped organs. They are located in the abdomen on either side of the spine. The kidneys filter your blood to remove excess water, salt, potassium, urea and other substances.
The waste products are then excreted as urine.
The ureters are thin, spaghetti-shaped tubules. They carry urine from the kidney to the bladder.
The bladder is a small, balloon-shaped organ located in the pelvis. In women, the bladder is located in front of the uterus. In men, the bladder is located just above the prostate gland.
The urethra is the tube through which urine exits the bladder. The urethra in women is far shorter than it is in men. In men, it has to pass through the prostate and the penis.
UTIs can involve the urethra (urethritis), bladder (cystitis), or kidneys (pyelonephritis). When the kidneys are involved, UTIs can be life threatening.
What causes a urinary tract infection?
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 a type of bacteria called 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 improper wiping and sexual intercourse.
Usually, the act of emptying the bladder (urinating) flushes the bacteria out of the urethra. If there are too many bacteria, urinating may not stop their spread.
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 decompensation after menopause)
- People with suppressed immune systems: Examples of situations in which the immune system is suppressed are HIV/AIDS and diabetes. People who take immunosuppressant medications such as chemotherapy for cancer also are at increased risk.
- Women who are sexually active: Sexual intercourse can introduce larger numbers of bacteria into the bladder.
- 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.
- 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.
- Breastfeeding has been found to decrease the risk for urinary tract infections in children.
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.
Symptoms of UTI
Symptoms of UTI depend upon what part of the urinary tract is infected.
Lower UTIs are infections of the urethra and bladder. Their symptoms include:
- burning with urination
- increased frequency of urination with scant amounts of urine being passed
- bloody urine
- cloudy urine
- urine that looks like cola or tea
- strong odor to urine
- pelvic pain (women)
- rectal pain (men)
Upper UTIs are infections of the kidneys. These are potentially life threatening, if bacteria move from the infected kidney into the blood.
This condition is called sepsis. Sepsis can cause dangerously low blood pressures, shock, and death. Symptoms of upper UTI include:
- pain and tenderness in the upper back and sides
Women who are pregnant and have symptoms of UTI should see their doctor right away. UTIs during pregnancy can cause premature delivery and high blood pressure.
UTIs during pregnancy are also more likely to spread to the kidneys.
When should people seek medical care for a UTI?
Any adult or child who develops any of the symptoms of a urinary tract infection needs to be evaluated by a medical professional, preferably within 24 hours.
Most medical offices can test urine for infection by using a quick urine “dipstick” test.
Someone who has symptoms of a lower urinary tract infection should call a health-care professional for an appointment, preferably on the same day that symptoms are recognized.
Someone who has symptoms of an upper urinary tract infection involving the kidneys should call a health-care professional immediately.
Depending on the situation, he or she will recommend either a visit to the office or to a hospital emergency department.
If someone has symptoms of a lower urinary tract infection and any of the following applies, he or she may have a urinary tract infection that can potentially be serious. Go to a hospital emergency department right away.
- Vomiting and inability to keep down clear fluids or medication
- Not better after taking antibiotics for two days
- Having diabetes or another disease that affects the immune system
- Taking medication that suppresses the immune system such as cancer chemotherapy
- Infants, children, and elderly people with any of the signs and symptoms of UTI should see their health-care professional as soon as possible or go to an emergency department for evaluation.
Fever, lethargy, and poor appetite may indicate a urinary tract infection in these groups, but they may also be signs of something more serious.
Urinary tract infections have the potential to make these vulnerable people very ill when the bacteria spread into the bloodstream.
Diagnosis of UTI
History and physical exam may suggest you have a lower or upper UTI.
Definitive diagnosis requires a “clean catch” urine specimen. This is urine collected from the middle of the urinary stream. Your doctor will instruct you how to do a clean catch. The goal is to avoid picking up bacteria from your skin.
Doctors will look for a large number of white blood cells in your urine. This can signal an infection. Your urine will also be cultured for bacteria. This can identify the cause of infection.
It can also help your doctor choose appropriate treatment.
If an upper UTI is suspected, you may also need a complete blood count (CBC) and blood cultures. These can make certain your infection hasn’t spread to the blood.
People with recurrent UTIs may need to be checked for obstructions. Some tests for this include:
- intravenous pyelogram (IVP) – this injected dye allows doctors to see your entire urinary tract
- cystoscopy, which uses a small camera to examine the bladder
During a cystoscopy, your doctor may remove a small piece of bladder tissue. This is called a biopsy. A biopsy can be used to rule out bladder cancer
Treatment of UTI
Antibiotics are used to treat UTIs. Lower UTIs can be treated with oral antibiotics. Upper UTIs require intravenous antibiotics.
Sometimes, bacteria develop resistance to antibiotics. Urine cultures can help your doctor select an effective antibiotic treatment.
Researchers are trying to develop a vaccine to prevent recurrent UTIs.
In the meantime, there are simple steps you can take to help prevent UTIs. WomensHealth.gov recommends:
- wiping from front to back after urinating or having a bowel movement
- drinking six to eight glasses of water daily
- drinking water after having sex
- not holding urine for long periods of time
- cleaning your vaginal and rectal areas daily
- taking showers instead of baths
- wearing comfortable underwear, tight fabric traps moisture
- wearing underpants with a cotton crotch
While these steps are useful, they don’t guarantee that you won’t get a UTI. Contact your medical provider whenever you have any symptoms of UTI.
If you have recurrent UTIs and use spermicides or a diaphragm, your doctor may recommend alternative birth control.