Each year, UTIs account for about 8 million doctor visits. Only respiratory infections occur more often. One woman in five will develop a UTI during her lifetime, with pregnant women being especially prone to them. People with diabetes also have a higher risk of UTIs because of changes of their immune system. Any disorder that suppresses the immune system increases the risk of a urinary infection.
Kidney stones form in the kidney out of substances in the urine.
A stone may stay in the kidney or break loose and travel down the urinary tract. Although a small stone may pass all of the way out of the body without causing too much pain, larger stones can become stuck in a ureter, the bladder, or the urethra, blocking the flow of urine and causing great pain. The prostate goes through two main periods of growth during a man's lifetime. Bladder trauma, which occurs occasionally in long-distance runners, is also manifested by bloody urine and is apparently due to bruising of the bladder's lining by prolonged periods of running. An empty bladder is believed to increase the risk of trauma by allowing opposing surfaces of the inside of the bladder to rub or bang against each other.