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Urinary Tract Infection: Overview and Risk Factors

Urinary tract infection (UTI) occurs when pathogenic bacteria enter the urethra and cause infection and inflammation. The urethra alone may be affected (urethritis), but more commonly the infection reaches the bladder (cystitis). The kidneys may also be involved (pyelonephritis), sometimes leading to sepsis. The remainder of this chapter focuses primarily on acute, uncomplicated cystitis.

UTIs are the most common bacterial infection in all age groups. The bacterial pathogens originate from the fecal flora. Escherichia coli (E coli) are the most common (80%–85%). Staphylococcus saprophyticus. Klebsiella, Proteus, and enterococcus may also cause infection.

Cystitis is generally a clinical diagnosis, and radiologic investigation is not required except in children who may have pyelonephritis. The usual symptoms of cystitis are dysuria, urinary frequency, and urinary urgency. However, urinary tract infections are frequently asymptomatic, particularly in the elderly. Pain in the suprapubic region may be reported, and hematuria and cloudy urine may occur as well. Patients with pyelonephritis typically present with fever, nausea/vomiting, and flank pain.

Among the elderly, confusion and other mental status changes may be the only signs of a urinary tract infection. Among children, symptoms typically include irritability, changes in eating habits, incontinence, and diarrhea. Vomiting may be the only symptom in young girls.

Risk Factors

  • Gender. More than 50% of women will have a urinary tract infection during their lifetime,1 with 20% of these women suffering 2 or more. In men, UTIs are rare (less than 0.1%), except in cases of anatomic abnormalities.
  • Sexual intercourse. A woman’s risk of infection is associated with frequency of intercourse. In addition, a new sexual partner and spermicide use are risk factors.
  • Bladder catheterization.
  • Urinary tract obstruction. Prostatic enlargement (benign prostatic hyperplasia or cancer) or inflammation, nephrolithiasis, and other obstructions raise the risk of UTI.
  • Anatomic abnormalities. These may include ureterovesical reflux.
  • Diabetes mellitus. Hyperglycemia and neurogenic bladder predispose to infection.
  • Menopause. Atrophic urogenital changes in women after menopause increase risk.


Urinary Tract Infection: Diagnosis and Treatment >>