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Urinary Tract Infection: Symptoms and Risk Factors

Urinary tract infections (UTIs) are one of the most common infections. Millions of UTIs occur in the United States every year, most commonly in young, sexually active women.

A UTI can begin anywhere along the urinary tract, which includes the urethra, bladder, and kidneys. Normally, these structures are sterile. That is, they have no bacteria, viruses, or other microbes living in them. A UTI occurs when one or more of these organs become infected, usually by bacteria (E. coli is the most common, causing up to 90 percent of cases).


The simplest type of UTI is urethritis, in which the urethra alone is infected. In this case, symptoms usually include only a burning sensation in the vaginal area or penis. Patients may also feel the need to urinate frequently.

More commonly, the bladder is infected, in which case the disease is called cystitis. Symptoms of cystitis include dysuria (pain when urinating), urinary frequency (the feeling of needing to urinate frequently), and urinary urgency (a feeling of not being able to hold in the urine). In some cases, pain in the lower abdomen occurs. In others, bloody or cloudy urine occurs.

In severe cases, the kidneys become infected, a condition called pyelonephritis, which is a potentially deadly infection that usually requires immediate hospitalization and intravenous antibiotic treatment. Patients with pyelonephritis appear seriously ill, with fever, nausea, vomiting, and severe side or back pain.

Among the elderly, confusion and other changes in mental functioning may be the only signs of a urinary tract infection.

In young children, symptoms typically include irritability, changes in eating habits, incontinence, and diarrhea. Vomiting may be the only symptom in young girls.

Risk Factors

  • Gender: In women, the urethra is shorter than in men, which allows bacteria to more easily move up the urethra and into the bladder to cause a UTI. More than 50 percent of women will have a UTI during their lifetime, and 20 percent of these women will have at least two UTIs. In men, UTIs are rare (less than 0.1 percent), except in men who have abnormalities of the bladder.
  • Sexual intercourse: A woman’s risk of infection is associated with her frequency of intercourse. This is because bacteria are often forced into the urinary tract during intercourse. In addition, a new sexual partner and the use of spermicides are risk factors.
  • Bladder catheterization, such as during a surgery or a hospital stay, increases the risk of UTI greatly.
  • Urinary tract obstruction also increases the risk significantly: Some causes of urinary tract obstruction include kidney stones and enlargement of the prostate gland in men.
  • Diabetes: Diabetic individuals are much more likely to have UTIs. This is partly due to increased sugar (glucose) in their urine, which fosters bacterial growth.
  • Menopause: Menopause also increases the risk for UTI due to weakening (atrophy) of the vaginal walls.


Urinary Tract Infection: Diagnosis and Treatment >>