The urinary system comprises the kidneys, ureters, bladder, and urethra. The kidneys act as a filter and remove wastes from the blood in the form of urine. The ureters carry urine from the kidneys to the bladder, where it is stored and then passed from the body through the urethra.
Normally, urine is sterile and free of foreign bacteria and viruses. However, bacteria can enter the urinary system through the urethra causing cystitis, or a urinary tract infection (UTI) as it is commonly called.
Symptoms of a UTI include: a burning sensation when urinating, frequent urination consisting of small amounts of urine, and the presence of blood in the urine.
Urinary tract infections are very common. After infancy, UTIs occur more often in females because their urethra is shorter and is closer to the anus. If a UTI is not detected and treated early, it can spread from the urethra to the bladder and the kidneys.