Urinary tract infection (UTI)

Symptoms

UTIs don't always cause symptoms. When they do, they may include:

• A strong urge to urinate that doesn't go away
• A burning feeling when urinating
• Urinating often, and passing small amounts of urine
• Urine that looks cloudy
• Urine that appears red, bright pink or cola-colored — signs of blood in the urine
• Strong-smelling urine
• Pelvic pain, in women — especially in the center of the pelvis and around the area of the pubic bone

In older adults, UTIs may be overlooked or mistaken for other conditions.

Causes

UTIs typically occur when bacteria enter the urinary tract through the urethra and begin to spread in the bladder. The urinary system is designed to keep out bacteria. But the defenses sometimes fail. When that happens, bacteria may take hold and grow into a full-blown infection in the urinary tract.

The most common UTIs occur mainly in women and affect the bladder and urethra.

• Infection of the bladder. This type of UTI is usually caused by Escherichia coli (E. coli). E. coli is a type of bacteria commonly found in the gastrointestinal (GI) tract. But sometimes other bacteria are the cause.

Having sex also may lead to a bladder infection, but you don't have to be sexually active to develop one. All women are at risk of bladder infections because of their anatomy. In women, the urethra is close to the anus. And the urethral opening is close to the bladder. This makes it easier for bacteria around the anus to enter the urethra and to travel to the bladder.

• Infection of the urethra. This type of UTI can happen when GI bacteria spread from the anus to the urethra. An infection of the urethra can also be caused by sexually transmitted infections. They include herpes, gonorrhea, chlamydia and mycoplasma. This can happen because women's urethras are close to the vagina.