Urinary tract infections (UTI's) happen when bacteria, typically E. coli, get into the bladder and grow, causing cystitis, an irritation of the bladder. There are many reasons women get these infections more often than men, but it all comes down to the design of their urinary tracts:
A woman's urethra is shorter than a man's, so the bacteria has a shorter distance to travel to reach the bladder.
Normally harmless strands of E. coli live in the lower intestine, and may be present in the rectum. The urethral opening in a woman is close to the rectum, so they don't have far to travel.
Sex can push bacteria into the urethra. As many as 90% of UTI's in young, sexually active women occur for this reason; this is commonly referred to as "honeymoon cystitis."
Pressure from a diaphragm or during pregnancy can make it difficult to completely empty the bladder, giving the bacteria a chance to grow. Hovering over the toilet can also withhold urine.
There is one place where men and women are on equal footing: catheter-related staph infections. Staphylococcus epidermidis, a bacteria normally found on human skin, likes to grow on medical plastics. It can be introduced into the bladder through a catheter, regardless of sex. Unlike E. coli, antibiotics are ineffective, but the infection will generally subside once the catheter is removed.
Posted 2920 day ago