Women who are sexually active tend to have more UTIs because sexual intercourse can result in bacteria being pushed into the urethra. Women who use diaphragms for birth control also may be at higher risk. Hormonal changes during pregnancy may increase the risk of a bladder infection as well.

Other risk factors in both men and women include anything that impedes the flow of urine, such as an enlarged prostate or a stone in the bladder. Changes in the immune system, which can occur with conditions such as diabetes, also can increase the risk of UTIs. So can the prolonged use of bladder catheters, which may be needed in people with chronic illnesses or in older adults.

Research funded by the National Institutes of Health suggests that a woman's blood type may play a role in her risk of recurrent infections of the bladder and urinary tract. Bacteria may be able to attach to cells in the urinary tract more easily in those with certain blood factors. But more research is needed to determine whether an association exists and whether it could be useful in identifying people at risk of recurrent infection.

Screening and diagnosis

If you have any symptoms of a bladder infection, talk to your doctor as soon as possible. If your doctor suspects you have a bladder infection, he or she may ask for a urine sample to determine whether bacteria, blood or pus is in your urine.

Complications

When treated promptly and properly, UTIs rarely lead to complications. But left untreated, a urinary tract infection can become something more serious than a set of uncomfortable symptoms.

An untreated bladder infection can lead to potentially serious complications, such as a kidney infection (pyelonephritis), which could be associated with a bacterial bloodstream infection (bacteremia). Also, kidney infections may permanently damage your kidneys. Young children and older adults are at the greatest risk of kidney damage due to bladder infections because their symptoms are often overlooked or mistaken for other conditions.