Risk factors in women

Urinary tract infections (UTIs) are most common in young to middle-aged sexually active women. Things that increase a woman's risk of getting UTIs include:

• Sexual activity, which pushes bacteria into the urethra. Sexual activity with the use of a diaphragm and spermicide raises the risk.
• Pregnancy. Pregnant women are at risk of developing asymptomatic bacteriuria, which in turn increases the risk of infections that cause symptoms. It also increases the risk of preterm labor.
• Previous UTIs.
• Use of feminine hygiene products that contain deodorant.
• Lack of estrogen, which allows bacteria that can cause UTIs to grow more easily in the vagina or urethra. Women who have gone through menopause are at increased risk for UTIs.

Risk factors in men

Things that increase a man's risk of UTIs include:

• Problems with the prostate gland. Men become increasingly prone to UTIs as they get older because of prostate problems, such as enlarged prostate (benign prostatic hyperplasia) and prostatitis.
• An uncircumcised penis.
• Anal intercourse.
• Unprotected sex with a woman who has a vaginal infection.
• HIV infection.

Risk factors in both women and men

Certain risk factors apply to both women and men. These include:

• Not drinking enough fluids. Drinking more fluids causes increased urination, reducing bacteria in the urinary tract and bladder.
• Having a catheter in place. A catheter is a small, flexible tube inserted through the urethra and into the bladder, allowing urine to drain. Bacteria can enter the catheter and start an infection. Most at risk are older adults who are in hospitals or who live in long-term care facilities. Catheterization also greatly increases the risk for asymptomatic bacteriuria.
• Kidney stones and other obstructions in the urinary tract. These may block the flow of urine, increasing the risk of bacterial infection.
• Diabetes. People with diabetes are at greater risk for UTIs because their immune systems are weakened. Also, long-term high blood sugar can damage the kidneys' filtering system (diabetic nephropathy).
• Structural problems of the urinary tract. These may be present at birth or develop later in life.