What Causes a Urinary Tract Infection?

Accounting for over 8 million doctor visits each year, wake forest urinary tract infections (UTIs) are one of the most common types of infections.  Caused by viral, fungal, or bacterial microbes, UTIs affect the kidneys, ureters, bladder, and urethra.  Women are more susceptible to UTIs than men and studies show that women have over a 50 percent chance of developing a UTI during their lifetime.  Given the prevalence of UTIs, people may be curious about what causes the infections as well as any risk factors to consider.

UTI Causes

While sometimes caused by viral or fungal mechanisms, most UTIs are bacterial and enter the urinary tract through the urethra before multiplying in the bladder.  The urinary system, much like the overall immune system, has defense mechanisms in place to keep out microscopic invaders.  When these defenses fail, bacteria can take hold, growing into a full-blown urinary tract infection.

The most common urinary tract infections affect the urethra and the bladder.

Urethra infection (urethritis):  Can occur when gastrointestinal bacteria spreads from the anus to the urethra.  And because the female urethra is anatomically close to the vagina, sexually transmitted diseases, like gonorrhea, chlamydia, and herpes, can cause urethritis.

Bladder infection (cystitis):  Also typically caused by gastrointestinal tract bacteria such as Escherichia coli (E. Coli).  Cystitis can be caused by sexual intercourse but sexual activity is not required to develop it.  Again, due to proximity of the urethra to the anus and the urethral opening to the bladder, all women are at risk of developing cystitis.

Risk Factors

As mentioned earlier, women are more prone to developing UTIs than men and many women experience multiple infections throughout their lives.  The following risk factors specific to women are:

-Female Anatomy:  Women have shorter urethras than men do.  As such, bacteria does not have to travel as far in women to reach the bladder.

-Sexual Activity:  Being sexually active or having a new sexual partner, can also increase a woman’s risk for developing a urinary tract infection.

-Birth Control:  Use of spermicidal agents or diaphragms for birth control may increase the risk.

-Menopause:  The decline in circulating estrogen resulting from menopause can lead to changes in the urinary tract that make the woman more susceptible to infection.

Non-gender specific risk factors include:

-Urinary Tract Abnormalities:  Some babies are born with urinary tract birth defects that increase their risk of developing UTIs.  These abnormalities do not allow urine to leave the body normally or cause back ups in the urethra.

-Urinary Tract Blockage:  UTI risk is elevated when urine gets trapped in the bladder such as with an enlarged prostate or kidney stones.

 -Suppressed Immune System:  When the immune system is suppressed, such as with diabetes, the body’s disease fighting mechanisms are impaired and the risk for UTIs can increase.

 -Use of Catheters:  While catheters can be used for people who cannot urinate on their own, they do carry an increased risk of UTIs.  Catheters are commonly used for those hospitalized, patients with neurological problems, or those paralyzed.

 -Recent Procedures:  If a patient has a urinary tract exam or surgical procedure that involves the use of medical instruments, development of a UTI is increased.

More on Urinary Tract Infections : How Long Do Urinary Tract Infections Last?