Urinary tract infections, more commonly known as UTIs, affect between 8 and 10 million people each year, Healthcommunities.com reports. Around 95 percent of UTIs result from bacteria gaining access to the urethra and ascending into the bladder, according to the Merck Manual. While most UTIs are uncomplicated, some are complicated, or related to structural or other abnormalities that make UTIs more likely to occur.
Gender
UTIs occur 50 times more often in women than men, the Merck Manual states. Infections occur more frequently in women because they have a shorter urethra, the tube that connects the meatus, or opening to the bladder, than men. Women are more likely to develop UTIs after sexual intercourse, especially if they use diaphragms, spermicides or spermicide-coated condoms.
Bacterial Causes
The most common cause of uncomplicated UTI, causing 80 percent of all UTIs, according to Healthcommunities.com, is infection with Escherichia coli, also known as E. coli, bacteria found in the gastrointestinal tract. While the bladder is normally sterile, the GI tract contains bacteria, which can travel to the urethra after bowel movements if poor cleaning technique is used or if stool remains on the skin, according to the Mayo Clinic. Other common bacterial causes of UTI include Staphylococcus saprophyticus, accounting for 5 to 15 percent of cases, and chlamydia and mycoplasma, common sexually transmitted bacteria, Healthcommunities.com reports.
In hospitalized patients, Klebsiella, Proteus, Enterobacter and Serratia bacteria cause around 40 percent of UTIs, according to the Merck Manual.
Structural Causes
People with congenital or acquired structural abnormalities of the urinary tract are more likely to develop UTIs. Around 35 to 45 percent of children with UTIs have vesicourethral reflux, or VUR, an abnormality of the valve that controls urine flow, the Merck Manual states. VUR can also occur in people with spinal cord injury.
Delayed Bladder Emptying
When the bladder doesn't empty completely or often, bacteria are more likely to stagnate and multiply, resulting in infection. Neurogenic bladder, often caused by injury to the nerves that control emptying; pregnancy; and prostate enlargement frequently cause delayed bladder emptying, according to the Merck Manual.
Indwelling Catheters
Indwelling urinary catheters, which drain urine automatically from the bladder into an attached bag, provide a direct route for bacteria to ascend into the bladder. Most people who have an indwelling urinary catheter for a prolonged period of time will develop an infection. Long-dwelling catheters should be inserted using sterile techniques and should be carefully cleaned and changed at least once a month to help prevent infection, MedlinePlus suggests.
