Chapter 82 Urinary Tract Infections
PATHOPHYSIOLOGY
Urinary tract infection (UTI) is the colonization of bacteria anywhere along the urinary tract. Infections can be of the lower urinary tract (urethra or bladder, also known as cystitis) or the upper urinary tract (ureters or the kidney, also known as pyelonephritis). The infectious agent is generally enteric in nature, most commonly Escherichia coli, followed by Klebsiella, Proteus, Enterococcus and coagulase-negative staphylococci. The presence of urine and stool around the urinary meatus allows the bacteria to proliferate and ascend upward to the urethra. Voiding is the first line of defense in preventing the causative agent from invading the urethra and bladder walls. Females have a shorter urethra, and bacteria enter at the end of micturition; males have a longer urethra and antibacterial properties that help to contribute to lower incidence of infection. UTI is second in frequency of occurrence of infections to upper respiratory tract infections.
There is an increased incidence in infants and young children learning to toilet-train. Children at risk are those with disorders that do not allow for full bladder emptying such as underlying defects of the urinary system, chronic disease, and neurologic disorders. Immunocompromised children are also at risk.
INCIDENCE
1. Neonatal-infancy period—boys increased incidence over girls
2. Beyond 1 year of life—girls have an increased incidence over boys (10:1)
3. Peak incidence not caused by structural abnormalities is 2 to 6 years
4. E. coli causes 80% of infections.
5. Most recurrence occurs after 3 to 6 months, with 60% to 80% of girls having a recurrence within 18 months.
6. Incidence of symptomatic UTI is lower than that of asymptomatic UTI.
7. UTI rarely leads to permanent damage, end-stage renal disease, or chronic pyelonephritis.
8. Uncircumcised boys typically experience two or three UTIs in childhood.
