Urinary Tract Infection - Introduction

The Urinary System and Its Defenses

The Urinary System

The urinary system helps maintain proper water and salt balance throughout the body and also expels urine from the body. It is made up of the following organs and structures:

• The two kidneys, located on each side below the ribs and toward the middle-back, play the major role in this process. They filter waste products, water, and salts from the blood to form urine.
• Urine passes from each kidney to the bladder through thin tubes called ureters.
• Ureters empty into the bladder, which rests on top of the pelvic floor. This is a muscular structure similar to a sling running between the pubic bone in front to the base of the spine.
• The bladder stores the urine, which is then eliminated from the body via another tube called the urethra, which is the lowest part of the urinary tract. (In men it is enclosed in the penis. In women it leads directly out.)

Defense Systems Against Bacteria

Infection does not always occur when bacteria are introduced into the bladder. A number of defense systems protect the urinary tract against infection-causing bacteria:

• Urine itself functions as an antiseptic, washing potentially harmful bacteria out of the body during normal urination. (Urine is normally sterile, that is, free of bacteria, viruses, and fungi.)
• The ureters are structurally designed to prevent urine from backing up into the kidney.
• The prostate gland in men secretes infection-fighting substances.
• The immune system in both sexes continuously fights bacteria and other harmful micro-invaders. In addition, immune system defenses and antibacterial substances in the mucous lining of the bladder eliminate many organisms.
• In normal fertile women, the vagina is colonized by lactobacilli, beneficial microorganisms that maintain a highly acidic environment (low pH). Acid is hostile to other bacteria. Lactobacilli also produce hydrogen peroxide, which helps eliminate bacteria and reduces the ability of E. coli to adhere to vaginal cells. (E. coli is the major bacterial culprit in urinary tract infections.)
• Some interesting research suggests that when bacteria infect the bladder, the cells that line the bladder literally sacrifice themselves and self-destruct (a process called apoptosis). In so doing, they fall away from the lining, carrying the bacteria with them. This eliminates about 90% of the E. coli.
• Some researchers have identified a possible natural antibiotic called human beta-defensin-1 (HBD-1), which fights E-coli within the female urinary and reproductive tracts.