Urinary Tract Infections

Infections of the urinary tract are the most common of all bacterial infections, and cause significant morbidity worldwide. The urinary system consists of the kidneys, ureters, prostate (in men), bladder, and urethra. On a daily basis, there is large variability in the amount and type of food and fluids that are consumed. The kidneys play a large role in maintaining fluid and electrolyte balance. Urine is produced by the kidneys as a result of filtration of the blood that passes through the kidneys. This urine travels through the ureter to the bladder, and together, the kidneys and bladder are considered the upper urinary tract.

Infection of the kidneys and prostate are termed pyelonephritis and prostatitis, respectively. The lower urinary tract consists of the bladder as well as the urethra, which is the organ that allows for excretion of urine from the bladder to outside of the body.

Infection of the bladder and urethra are termed cystitis and urethritis, respectively. Both the upper and the lower urinary tracts can be infected with a variety of organisms, producing different symptoms and consequences, and requiring different treatments.

Urinary tract infections (UTIs) are frequently defined by detection of pathogenic microorganisms in the urine, urethra, bladder, kidney, or prostate. When a sample of urine is appropriately collected and cultured, the growth of more than 105 organisms from 1 milliliter of urine is considered an infection. However, if a patient is experiencing symptoms of an UTI, then there is often a lower threshold to the number of bacteria that need to be present to diagnose and infection. Bacteria can enter the urinary system from direct entry through the urethra, or they can be introduced as a consequence of catheter insertion or a surgical procedure.